Mean Error

This paper investigates the efficiency of Black-Scholes model used for valuation of call option contracts written on Eight Indian stocks quoted on NSE. It has been generally observed that the B & S Model misprices options considerably on several occasions and the volatilities are 'high for options which are highly overpriced. Mispriced worsen with the increased in volatility of the underlying stocks. In most of cases options are also highly underpriced by the model. In this research paper, the theoretical options prices of Nifty stock call options are calculated under the B & S Model. These theoretical prices are compared with the actual quoted prices in the market to gauge the pricing accuracy.

Accurate prediction of burst pressure plays a central role in engineering design and integrity assessment of oil and gas pipelines. Theoretical and empirical solutions for such prediction are evaluated in this paper relative to a burst pressure database comprising more than 100 tests covering a variety of pipeline steel grades and pipe sizes. Solutions considered include three based on plasticity theory for the endcapped, thin-walled, defect-free line pipe subjected to internal pressure in terms of the Tresca, von Mises, and ZL (or Zhu-Leis) criteria, one based on a cylindrical instability stress (CIS) concept, and a large group of analytical and empirical models previously evaluated by Law and Bowie (International Journal of Pressure Vessels and Piping, 84, 2007: 487e492). It is found that these models can be categorized into either a Tresca-family or a von Mises-family of solutions, except for those due to Margetson and Zhu-Leis models. The viability of predictions is measured via statistical analyses in terms of a mean error and its standard deviation. Consistent with an independent parallel evaluation using another large database, the Zhu-Leis solution is found best for predicting burst pressure, including consideration of strain hardening effects, while the Tresca strength solutions including Barlow, Maximum shear stress, Turner, and the ASME boiler code provide reasonably good predictions for the class of line-pipe steels with intermediate strain hardening response.

Murici (Byrsonima sericea) and ingá (Ingá edulis) desorption isotherms were determined by the gravimetric method at two different temperatures. Experimental data was adjusted to five sorption models of Langmuir, Oswin, Anderson, GAB and Peleg. Sorption isotherms were determined gravimetrically by exposing the samples to controlled atmospheres produced by saturated salt solutions. The coefficient of regression R2 and mean squares of

Evapotranspiration plays a central role in the water balance of arid and semi-arid areas, as it is the major loss flux. The spatial estimation of actual evapotranspiration is thus of critical importance for hydrologic, environmental and agricultural purposes. This study therefore applied the Surface Energy Balance System for turbulent heat fluxes (SEBS) algorithm to determine actual evapotranspiration in the Upper Manyame catchment in Zimbabwe. The SEBS algorithm was run using atmospherically corrected MODIS satellite imagery on nine clear skies days stretching from 2003 to 2005. SEBS determined actual evapotranspiration was evaluated based on two criteria over Harare-Kutsaga and Grasslands research stations. Firstly, a plausibility or physical consistency check was applied by which SEBS actual evapotranspiration estimates were compared to FAO Penman-Monteith potential evapotranspiration estimates. On average, it was observed that SEBS actual evapotranspiration estimates were physically consistent. SEBS estimates were 36.5% and 76.5% of potential evapotranspiration over Harare-Kutsaga and Grasslands stations, respectively. However, on a few days over Grasslands station SEBS actual evapotranspiration estimates were physically inconsistent as they were greater than potential evapotranspiration. SEBS actual evapotranspiration estimates were also evaluated against actual evapotranspiration from the advection aridity equation. Over Harare-Kutsaga the mean error showed a slight underestimation of 0.32 mm d À1 by SEBS and the mean absolute error was 0.5 mm d À1. However, over Grasslands station the results were not as good as the mean error and mean absolute error showed an overestimation 2.6 mm d À1. This was relatively high. The discussed reasons for the relatively high overestimation errors over Grasslands station include; roughness parameterisation, the spatial variability of input temperature data and heterogeneity. An analysis of the evaporative behaviour of the different land cover types in the catchment showed that: water bodies, closed broadleaved deciduous forests, and open broadleaved deciduous forests had relatively higher mean actual evapotranspiration rates and yet these land cover types constituted less than 5% of the catchment area. Open grasslands were observed to have low evaporative behaviour. Overall this study showed that SEBS has potential for estimating spatial actual evapotranspiration and providing useful information that can be used for water resources and environmental management and planning.

A prospective study was conducted at Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife, Nigeria, between 3 January and 31May 2004, to compare the accuracy of clinical and ultrasonographic estimation of foetal weight at term. One hundred pregnant women ...

We consider the fundamental problem of estimating the mean of a vector $y=X\beta+z$, where $X$ is an $n\times p$ design matrix in which one can have far more variables than observations, and $z$ is a stochastic error term--the so-called "$p>n$" setup. When $\beta$ is sparse, or, more generally, when there is a sparse subset of covariates providing a close approximation to the unknown mean vector, we ask whether or not it is possible to accurately estimate $X\beta$ using a computationally tractable algorithm. We show that, in a surprisingly wide range of situations, the lasso happens to nearly select the best subset of variables. Quantitatively speaking, we prove that solving a simple quadratic program achieves a squared error within a logarithmic factor of the ideal mean squared error that one would achieve with an oracle supplying perfect information about which variables should and should not be included in the model. Interestingly, our results describe the average performance of the lasso; that is, the performance one can expect in an vast majority of cases where $X\beta$ is a sparse or nearly sparse superposition of variables, but not in all cases. Our results are nonasymptotic and widely applicable, since they simply require that pairs of predictor variables are not too collinear.

Abstract-Jitter is the limiting effect for high speed analog-to-digital converters with high resolution and wide digitization bandwidth, which are required in receivers in order to support high data rates. The rapid development of digital wireless system has led to a need of high ...

We introduce, for the first time, a new class of Birnbaum-Saunders nonlinear regression models potentially useful in lifetime data analysis. The class generalizes the regression model described by Rieck and Nedelman [1991, A log-linear model for the Birnbaum-Saunders distribution, Technometrics, 33, 51-60]. We discuss maximum likelihood estimation for the parameters of the model, and derive closedform expressions for the second-order biases of these estimates. Our formulae are easily computed as ordinary linear regressions and are then used to define bias corrected maximum likelihood estimates. Some simulation results show that the bias correction scheme yields nearly unbiased estimates without increasing the mean squared errors. We also give an application to a real fatigue data set.

In this paper, we propose a novel approach to econometric forecasting of stationary and ergodic time series within a panel-data framework. Our key element is to employ the (feasible) bias-corrected average forecast. Using panel-data sequential asymptotics we show that it is potentially superior to other techniques in several contexts. In particular, it is asymptotically equivalent to the conditional expectation, i.e., has an optimal limiting mean-squared error. We also develop a zeromean test for the average bias and discuss the forecast-combination puzzle in small and large samples. Monte-Carlo simulations are conducted to evaluate the performance of the feasible bias-corrected average forecast in …nite samples. An empirical exercise based upon data We are especially grateful for the comments and suggestions given by two anonymous referees,

Solar panels are frequently used in wireless sensor nodes because they can theoretically provide quite a bit of harvested energy. However, they are not a reliable, consistent source of energy because of the Sun's cycles and the everchanging weather conditions. Thus, in this paper we present a fast, efficient and reliable solar prediction algorithm, namely, Weather-Conditioned Moving Average (WCMA) that is capable of exploiting the solar energy more efficiently than state-of-the-art energy prediction algorithms (e.g. Exponential Weighted Moving Average EWMA). In particular, WCMA is able to effectively take into account both the current and past-days weather conditions, obtaining a relative mean error of only 10%. When coupled with energy management algorithm, it can achieve gains of more than 90% in energy utilization with respect to EWMA under the real working conditions of the Shimmer node, an active sensing platform for structural health monitoring.

We introduce, for the first time, a new class of Birnbaum-Saunders nonlinear regression models potentially useful in lifetime data analysis. The class generalizes the regression model described by Rieck and Nedelman [1991, A log-linear model for the Birnbaum-Saunders distribution, Technometrics, 33, 51-60]. We discuss maximum likelihood estimation for the parameters of the model, and derive closedform expressions for the second-order biases of these estimates. Our formulae are easily computed as ordinary linear regressions and are then used to define bias corrected maximum likelihood estimates. Some simulation results show that the bias correction scheme yields nearly unbiased estimates without increasing the mean squared errors. We also give an application to a real fatigue data set.

A group contribution technique is proposed t . ~ predict the coefficients in the heat capacity correlation, C, = a + bT + : + dT2 , for solid inorganic salts. The results fiom this C T work are compared with fits to experimental data fiom the literature. It is shown to give good predictions for both simple and complex solid inorganic salts. Literature heat capacities for a large number (664) of solid inorganic salts covering a broad range of cations (129), anions (17) and ligands (2) have been used in regressions to obtain group contributions for the parameters in the heat capacity temperature function. A mean error of 3.18% is found when predicted values are compared with literature values for heat DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or procxss disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. c capacity at 298 O K . Estimates of the error standard deviation fiom the regression for each additivity constant are also determined.

A new methodology is developed for estimating unemployment or employment characteristics in small areas, based on the assumption that the sample totals of unemployed and employed individuals follow a multinomial logit model with random area effects. The method is illustrated with UK labour force data aggregated by sex-age groups. For these data, the accuracy of direct estimates is poor in comparison with estimates that are derived from the multinomial logit model. Furthermore, two different estimators of the mean-squared errors are given: an analytical approximation obtained by Taylor linearization and an estimator based on bootstrapping. A simulation study for comparison of the two estimators shows the good performance of the bootstrap estimator.

Ordinal data are often modeled using a continuous latent response distribution, which is partially observed through windows of adjacent intervals de¯ned by cutpoints. In this paper we propose the beta distribution as a model for the latent response. The beta distribution has several advantages over the other common distributions used, e.g., normal and logistic. In particular, it enables separate modeling of location and dispersion e®ects which is essential in the Taguchi method of robust design. First, we study the problem of estimating the location and dispersion parameters of a single beta distribution (representing a single treatment) from ordinal data assuming known equispaced cutpoints. Two methods of estimation are compared: the maximum likelihood method and the method of moments. Two methods of treating the data are considered: in raw discrete form and in smoothed continuousized form. A large scale simulation study is carried out to compare the di®erent methods. The mean square errors of the estimates are obtained under a variety of parameter con¯gurations. Comparisons are made based on the ratios of the mean square errors (called the relative e±ciencies). No method is universally the best, but the maximum likelihood method using continuousized data is found to perform generally well, especially for estimating the dispersion parameter. This method is also computationally much faster than the other methods and does not experience convergence di±culties in case of sparse or empty cells. Next, the problem of estimating unknown cutpoints is addressed. Here the multiple treatments setup is considered since in an actual application, cutpoints are common to all treatments, and must be estimated from all the data. A two-step iterative algorithm is proposed for estimating the location and dispersion parameters of the treatments, and the cutpoints. The proposed beta model and McCullagh's (1980) proportional odds model are compared by¯tting them to two real data sets.

This paper is concerned with estimating the solutions of numerically ill-posed least squares problems through Tikhonov regularization. Given a priori estimates on the covariance structure of errors in the measurement data b, and a suitable statistically-chosen σ, the Tikhonov regularized least squares functional J(σ) = Ax − b 2 W b + 1/σ 2 D(x − x 0) 2 2 , evaluated at its minimizer x(σ), approximately follows a χ 2 distribution withm degrees of freedom. Herem = m + p − n for A ∈ R m×n , D ∈ R p×n , matrix W b is the inverse covariance matrix of the mean 0 normally distributed measurement errors e in b, and x 0 is an estimate of the mean value of x. Using the generalized singular value decomposition of the matrix pair [W 1/2 b AD], σ can then be found such that the resulting J follows this χ 2 distribution, Mead and Renaut (2008). Because the algorithm explicitly relies on the direct solution of the problem obtained using the generalized singular value decomposition it is not practical for large scale problems. Here the approach is extended for large scale problems through the use of the Newton iteration in combination with a Golub-Kahan iterative bidiagonalization of the regularized problem. The algorithm is also extended for cases in which x 0 is not available, but instead a set of measurement data provides an estimate of the mean value of b. The sensitivity of the Newton algorithm to the number of steps used in the Golub-Kahan iterative bidiagonalization, and the relation between the size of the projected subproblem and σ are discussed. Experiments presented contrast the efficiency and robustness with other standard methods for finding the regularization parameter for a set of test problems and for the restoration of a relatively large real seismic signal. An application for image deblurring also validates the approach for large scale problems. We conclude that the presented approach is robust for both small and large scale discretely ill-posed least squares problems.

Two approaches for downscaling and calibrating error estimates from ensemble precipitation forecasts are evaluated; the two methods are intended to be used to produce flood forecasts based on global weather forecasts in ungauged river basins. The focus of this study is on the ability of the approaches to reproduce observed forecast errors when applied to daily precipitation forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS) for a 10-day forecast period. The two approaches are bias correction with spatial disaggregation (BCSD) and an analog technique. Mean forecast errors and skills are evaluated with respect to Tropical Rainfall Monitoring Mission (TRMM) observations over the Ohio River basin for the period 2002–06 for daily and 5-day accumulations and for 0.25° and 1° spatial resolutions. The Ohio River basin was chosen so that a relatively dense gauge-based observed precipitation dataset could also be used in the evaluati...

Evapotranspiration plays a central role in the water balance of arid and semi-arid areas, as it is the major loss flux. The spatial estimation of actual evapotranspiration is thus of critical importance for hydrologic, environmental and agricultural purposes. This study therefore applied the Surface Energy Balance System for turbulent heat fluxes (SEBS) algorithm to determine actual evapotranspiration in the Upper Manyame catchment in Zimbabwe. The SEBS algorithm was run using atmospherically corrected MODIS satellite imagery on nine clear skies days stretching from 2003 to 2005. SEBS determined actual evapotranspiration was evaluated based on two criteria over Harare-Kutsaga and Grasslands research stations. Firstly, a plausibility or physical consistency check was applied by which SEBS actual evapotranspiration estimates were compared to FAO Penman-Monteith potential evapotranspiration estimates. On average, it was observed that SEBS actual evapotranspiration estimates were physically consistent. SEBS estimates were 36.5% and 76.5% of potential evapotranspiration over Harare-Kutsaga and Grasslands stations, respectively. However, on a few days over Grasslands station SEBS actual evapotranspiration estimates were physically inconsistent as they were greater than potential evapotranspiration. SEBS actual evapotranspiration estimates were also evaluated against actual evapotranspiration from the advection aridity equation. Over Harare-Kutsaga the mean error showed a slight underestimation of 0.32 mm d À1 by SEBS and the mean absolute error was 0.5 mm d À1. However, over Grasslands station the results were not as good as the mean error and mean absolute error showed an overestimation 2.6 mm d À1. This was relatively high. The discussed reasons for the relatively high overestimation errors over Grasslands station include; roughness parameterisation, the spatial variability of input temperature data and heterogeneity. An analysis of the evaporative behaviour of the different land cover types in the catchment showed that: water bodies, closed broadleaved deciduous forests, and open broadleaved deciduous forests had relatively higher mean actual evapotranspiration rates and yet these land cover types constituted less than 5% of the catchment area. Open grasslands were observed to have low evaporative behaviour. Overall this study showed that SEBS has potential for estimating spatial actual evapotranspiration and providing useful information that can be used for water resources and environmental management and planning.

In previous work on acoustical lens effect, a model based on the annular decomposition of an axisymmetric focused piezoelectric transducer was described and found to be in agreement with FEM and experimental results. The design of a focused transducer must take into account both radiation and transduction properties. These complex models such as FEM, FDTD and PSTD methods take into

To assess the literature on accuracy and clinical performance of computer technology applications in surgical implant dentistry. Materials and Methods: Electronic and manual literature searches were conducted to collect information about (1) the accuracy and (2) clinical performance of computer-assisted implant systems. Meta-regression analysis was performed for summarizing the accuracy studies. Failure/complication rates were analyzed using random-effects Poisson regression models to obtain summary estimates of 12-month proportions. Results: Twenty-nine different image guidance systems were included. From 2,827 articles, 13 clinical and 19 accuracy studies were included in this systematic review. The meta-analysis of the accuracy (19 clinical and preclinical studies) revealed a total mean error of 0.74 mm (maximum of 4.5 mm) at the entry point in the bone and 0.85 mm at the apex (maximum of 7.1 mm). For the 5 included clinical studies (total of 506 implants) using computer-assisted implant dentistry, the mean failure rate was 3.36% (0% to 8.45%) after an observation period of at least 12 months. In 4.6% of the treated cases, intraoperative complications were reported; these included limited interocclusal distances to perform guided implant placement, limited primary implant stability, or need for additional grafting procedures. Conclusion: Differing levels and quantity of evidence were available for computer-assisted implant placement, revealing high implant survival rates after only 12 months of observation in different indications and a reasonable level of accuracy. However, future long-term clinical data are necessary to identify clinical indications and to justify additional radiation doses, effort, and costs associated with computer-assisted implant surgery.

A comprehensive, physically based model of snow accumulation, redistribution, sublimation, and melt for open and forested catchments was assembled, based on algorithms derived from hydrological process research in Russia and Canada. The model was used to evaluate the long-term snow dynamics of a forested and an agricultural catchment in northwestern Russia without calibration from snow observations. The model was run with standard meteorological variables for the two catchments, and its results were tested against regular surface observations of snow accumulation throughout the winter and spring period for 17 seasons. The results showed mean errors in comparison to observations of less than 3% in estimating snow water equivalent during the winter and melt seasons. Snow surface evaporation and blowing snow were found to be small components of the mass balance, but intercepted snow sublimation removed notable amounts of snow over the winter from the forested catchment. Average snow accumulation was 15% higher in the open catchment, largely due to a lack of intercepted snow sublimation. Melt rates were 23% higher in the open than in the forest, but the effect on melt duration was suppressed by the smaller premelt accumulation in the forest. Only a moderate sensitivity of snow accumulation to forest leaf area was found, while a substantial variation was observed from season to season with changing weather patterns. This suggests that the ensemble of snow processes is more sensitive to variations in atmospheric processes than in vegetation cover. The success in using algorithms from both Canada and Russia in modeling snow dynamics suggests that there may be a potential for large-scale transferability of the modeling techniques.

The possibilities of adapting the Modern Analogs Technique (MAT) based on planktonic foraminifers for estimating sea-surface temperatures (SST) in the Mediterranean during the Pliocene are discussed in this article. The calibration database used comprises 684 core-top samples distributed in the North Atlantic and the Mediterranean. MAT estimates show an imperceptible bias (−0.03°C; σ = 0.59) and a low mean error of estimates (0.42°C; σ = 0.42) when applied over the samples of the calibration dataset. The procedure used for assimilating the Pliocene taxonomic categories to those of the modern assemblages results in an increase from 17 to 40 in the number of samples showing an error N 2°C when applied over the calibration database. However, the precision of MAT does not diminish when these samples are removed from the dataset. This methodology was used for obtaining SST estimates of late-middle Pliocene-earliest Pleistocene samples from ODP-site 975 (Menorca area), which have close modern analogs within the calibration database. In order to compare this technique with an additional proxy, we measured also δ 18 O values of G. bulloides tests from these samples. The results obtained show a good agreement on the whole, which corroborates the validity of the technical approach proposed.

We develop a statistical method for discriminating and classifying multivariate nonstationary signals. It is assumed that the processes that generate the signals are characterized by their time-evolving spectral matrix-a description of the dynamic connectivity between the time series components. Here, we address two major challenges: first, data massiveness and second, the poor conditioning that leads to numerically unstable estimates of the spectral matrix. We use the SLEX library (collection bases functions consisting of localized Fourier waveforms) to extract the best set of timefrequency features that best separate classes of time series. The SLEX approach yield readily interpretable results since it is a time-dependent analogue of Fourier approach to stationary time series. Moreover, it uses computationally efficient algorithms to enable handling of large data sets. We estimate the SLEX spectral matrix by shrinking the initial SLEX periodogram matrix estimator towards the identity matrix. The resulting shrinkage estimator has lower mean-squared error than the classical smoothed periodogram matrix. A leave-one out analysis for predicting motor intent (left vs. right movement) using electroencephalograms indicates that the proposed SLEX-Shrinkage method gives robust estimates of the evolutionary spectral matrix and good classification results.

In order to optimize the accuracy of imaging in Gamma Knife radiosurgery using the image fusion options available in the Leksell gamma plan. Phantom images from 1.5 Tesla MRI Scan (Magnetom vision-Siemens) and Computed Tomography images from Philips Brilliance 16 CT scanner were used for image fusion in Gammaplan treatment planning system. The images were fused using co-registration technique using multiview and imagemerge modules. Stereotactic coordinates were then calculated for known targets. Vector distances from the centre of the Leksell coordinate system to five known targets were measured in CT, MR and CT-MR fused images and compared with geometrical measurements. The mean values of maximum absolute errors were 0.34 mm ,0.41 mm.0.38 mm (along x-axis), 0.43 mm, 1.53 mm, 0.62 mm (along y-axis) and 0.75 mm 2.02 mm, 0.93 mm (along z-axis) for CT ,MR and CT-MR fused image data respectively. The mean error in calculating the vector distances from the center of the Leksell coordinate system (100, 100, 100) to the known target volumes are 0.22 mm, 0.8 mm and 0.43 mm for CT, MR and CT-MR fused images, respectively. Image fusion functions available in gamma plan are useful for combining the features of CT and MR imaging modalities. These methods are highly useful in clinical situations where the error associated with Magnetic Resonance Imaging is beyond acceptable levels.

Ingeniería e Investigación Universidad Nacional de Colombia revii_bog@unal.edu.co ISSN (Versión impresa): 0120-5609 COLOMBIA ... Everaldo Joaquín Montes Montes / Ramiro Torres Gallo / Ricardo David Andrade Pizarro / Omar Andrés Pérez Sierra / José Luis Marimon ...

This work seeks to analyze empirically the coherence of the VaR and the Expected Shortfall by the definition of Artzner et al. (1997) at the Brazilian Stock Market (Bovespa), calculated with three methodologies: the historical simulation, the analytical approach with EWMA volatility from RiskMetricsTM and the hybrid approach developed by Boudoukh et al. (1998). The sample includes the ten most

The accuracy of Geosat satellite altimetry over the Greenland ice sheet is evaluated by comparing the measured heights to radar elevations from the airborne Greenland Aerogeophysics Project. At the center of the ice sheet where the ice surface is nearly level, surface comparisons show a fit at the 1 to 3 m level as expected, but even at moderately sloping ice regions (0.3 ø-0.6ø), satellite altimetry mean errors in the range of 10 to 35 m are observed. These errors are found for slope-corrected and waveformretracked data, so most previous accuracy estimates of current satellite altimetry ice sheet elevations in regions of sloping or undulating ice appear to be too optimistic. 1. Introduction Satellite altimetry is generally recognized as the most extensive mad valuable source of elevation data for topographical and glaciological studies of ice sheets mad ice shelves. Altimetry over ice sheets mad ice shelves is primarily introduced in two research areas, determination of the ice sheet topography mad of possible elevation changes versus time. Although a number of investigations have studied possible temporal changes by means of satellite altimetry [e.g. Zwally et al., 1989; Lingle et al., 1990; Andersen, 1994], only limited efforts have been made to obtain an independent evaluation of the accuracy of the surface heights themselves [see Thonms et al., 1994]. The internal consistency of satellite altimetry has previously been examined through crossover analysis [Brooks et al., 1978; Zwally et al., 1983, 1987], and error budgets derived from analysis of statistical estimators are presented by, e.g., Lingle et al. [1990] mad HerzfeM et al. [1993]. However, an independent, absolute assessment has been difficult, primarily because of lack of groundtruth data. Such data are scarce, both in Greenland mad Antarctica, are typically clustered around areas of particular glaciological interest, mad are often of insufficient accuracy. In Greenland, for example, most data previously used for evaluation cluster on the southern ice dome around the drilling site of Dye-3, where the terrain is nearly level mad not ideal for evaluating satellite altimetry. In the present investigation we examine Geosat altimetry by comparing it to airborne radar profile data from the Greenland Aerogeophysics Project [Brozena et al., 1993], a unique airborne geophysical survey of Greenland, which provided an island-wide coverage of high

The aim of this paper is to propose two new hybrid cellular techniques for mobile positioning in UMTS. Developed methods are entirely mobile-based since no modifications are required on the network side. Proposed techniques exploit signal strength and delay spread measurements from at least two base stations. The estimation accuracy of the presented location techniques has been assessed by measurement campaigns performed in various network configurations and in diverse propagation environments. Measurement results have indicated that the accuracy of positioning based on signal strength measurements can be improved in majority of propagation environments if one of the proposed methods is used. Namely, in a measured area in an urban micro cellular environment the mean error in the range estimation has been reduced from 58 m to 30 m when introduced method has been used. Slightly smaller improvement (30%) has been observed in macro cellular urban and no improvement -in macro cellular su...

We propose a new method to estimate the cumulative hazard function and the corresponding distribution function of survival times under randomly left truncated and right censored observations (LTRC). For the density function, a new kerneltype estimator is also presented obtained by the convolution of a kernel with this new estimator of the distribution function. The new methodology is based on presmoothing ideas, the estimation of the conditional expectation m of the censoring indicator. Asymptotic properties, including an almost sure representation, strong consistency, asymptotic normality and mean integrated squared error expressions, are given. It is shown that the presmoothed modification leads to a gain in terms of asymptotic mean squared error. The practical performance of these estimators and the efficiency with respect to the classical ones are illustrated in a simulation study. Finally, they are used to analyze the lifetime in a real data example.

The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant along-track sea surface height (SSH) signal: the case of tropical cyclone Isabel is presented here. The Sand C-band measurements are used because they are less impacted by rain than the Ku-band, and new sea state bias (SSB) and wet troposphere corrections are proposed. More accurate strong altimeter wind speeds are computed thanks to the Young algorithm. Ocean signals not related to atmospheric pressure can be removed with accuracy, even within a Near Real Time context, by removing the maps of sea level anomaly (SLA) provided by SSALTO/Duacs. In the case of Extra-Tropical Depressions, the classical altimeter processing can be used. Ocean signal not related to atmospheric pressure is along-track filtered. The sea level pressure (SLP)-SLA relationship is investigated for the North Atlantic, North Pacific and Indian oceans; three regression models are proposed allowing restoring an altimeter SLP with a mean error of 5 hPa if compared to ECMWF or buoys SLP. The analysis of barotropic simulation outputs points out the regional variability of the SLP/Model Sea Level relationship and the wind effects.

Context. To investigate the link between the International Celestial Reference Frame (ICRF) and its optical Hipparcos-based representation on the northern hemisphere. Aims. To present results of a pilot investigation on the astrometry of 59 northern ICRF sources. Methods. We used the 0.6 m Zeiss telescope at Belogradchik Observatory, Bulgaria. The optical CCD source positions were referred to the UCAC2 catalog. Improved astrometric methods were applied including telescope shifting between exposures, (x, y) Gaussian measurements within 1 full width at half maximum, and the observation of a large number of frames per source. The huge amount of data generated was treated with a new astrometric package, PRAIA (Platform for Reduction of Astronomical Images Astrometrically). Results. Average and standard deviation for the optical minus radio position offsets were +6 mas (51 mas) and +7 mas (57 mas) for RA and Dec, respectively. The errors of all (x, y) measurements from Gaussian fits displayed a typical distribution with respect to magnitude, dependent on the sky transparency. For the ICRF objects, the (x, y) errors per source ranged from 50 mas to 100 mas. The RA and Dec reduction mean errors were 46 mas. Conclusions. No large scale systematic errors with respect to RA or Dec were found within the attained position precision. Comparison with three independent telescope/catalog datasets shows that the precision obtained here represents an important improvement on previous works. In comparison with the southern hemisphere, more astrometry on ICRF sources are needed in the north, and it is shown here that the continuation of this program can fill this need.

Ingeniería e Investigación Universidad Nacional de Colombia revii_bog@unal.edu.co ISSN (Versión impresa): 0120-5609 COLOMBIA ... Everaldo Joaquín Montes Montes / Ramiro Torres Gallo / Ricardo David Andrade Pizarro / Omar Andrés Pérez Sierra / José Luis Marimon ...

We tested the hypothesis that the mechanism, rate, and extent of in vivo placental transfer of dideoxynucleoside drugs against human immunodeficiency virus can be predicted by the in vitro perfused human placenta and the drug octanol-water partition coefficient. Near-term pregnant macaques (Macaca nemestrina ) underwent long-term catheterization for the administration of 4 dideoxynucleosides against human immunodeficiency virus: zidovudine, didanosine, zalcitabine, and stavudine. Maternal plasma, fetal plasma, and amniotic fluid concentrations were determined frequently after intravenous bolus and/or infusion of the drugs administered into the maternal or fetal circulation on separate occasions. Antipyrine was included in all experiments as a marker of placental blood flow. The mechanism, rate, and extent of placental transfer of the 4 dideoxynucleosides in perfused human placenta were determined and compared with the findings obtained by others. The mechanism and rate of the antipyrine-normalized placental transfer of the 4 dideoxynucleosides in perfused human placenta were highly correlated with those observed in vivo. The extent of placental transfer (fetal/maternal steady-state plasma concentration ratio) was also highly correlated with both the antipyrine-normalized placental transfer clearance (clearance index) determined in the in vitro perfused human placenta model (r 2 = 0.95, in vitro clearance-index model) and the drug octanol-water partition coefficient (r 2 = 0.99, in vitro partition-coefficient model). To determine the predictive capacity of these correlative models, we predicted the fetal/maternal steady-state plasma concentration ratio of each drug after excluding the data on that drug from the model fit. Both in vitro models to predict in vivo placental transfer of drug models resulted in good predictions of the observed fetal/maternal steady-state plasma concentration ratio (mean error: in vitro clearance-index model = -1. 2%; in vitro partition-coefficient model = 3.9%). We propose that our models will accurately predict the extent of placental transfer of dideoxynucleoside drugs against human immunodeficiency virus. The models may also be applicable to other classes of drugs, regardless of therapeutic category, provided that these drugs passively diffuse across the placenta. Such a result will expedite phase 1 clinical trials of drugs in pregnant women.

We present relative astrometric measurements of visual binaries made during the first semester of 2007, with the Pupil Interferometry Speckle camera and COronagraph (PISCO) at the 102-cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 226 new measurements of 214 objects, with angular separations

The velocity–azimuth display (VAD) technique was designed to estimate the areal mean vertical profile of the horizontal wind above a ground-based Doppler radar. The method uses radial velocity observations under the assumption of a linear wind field, though it encounters difficulty when the observations are contaminated by velocity ambiguities, large noise, and when viable data exist only over a restricted azimuthal range. The method suggested in this paper uses gradients of radial velocity, rather than only the velocity itself, to derive wind profiles and thus is termed the gradient velocity–azimuth display (GVAD) technique. Both the VAD and GVAD methods are tested first on simulated data to examine their sensitivity to different type of errors in radial velocity. The retrieved mean wind profiles are shown to be insensitive to random errors in radial velocity, even at large amplitude. However, the VAD method is very sensitive to systematic errors caused by velocity ambiguities. The...

In this paper we assess accuracy of some commonly used estimators of upper quantiles of a right skewed distribution under both parameter and model uncertainty. In particular, for each of log-normal, log-logistic, and log-double exponential distributions, we study the bias ...

Central pattern generated walking for bipedal robots has proven to be a versatile and easily implementable solution that is used by several robot soccer teams in the RoboCup Humanoid Soccer League with great success. However, the forward character of generating motor commands from an abstract, rhythmical pattern does not inherently provide the means for controlling the precise location of footsteps. For implementing a footstep planning gait control, we developed a step prediction model that estimates the location of the next footstep in Cartesian coordinates given the same inputs that control the central pattern generator. We used motion capture data recorded from walking robots to estimate the parameters of the prediction model and to verify the accuracy of the predicted footstep locations. We achieved a precision with a mean error of 1.3 cm.

In selected patients undergoing epilepsy surgery, subdural electrode grids play an important role in localizing the epileptogenic zone and identifying eloquent cortex. Determining the relationship of the electrodes to underlying brain architecture traditionally has been difficult. This report describes and validates the use of an original computer-aided method that displays a representation of the electrode positions, based on postimplantation CT or MR findings, coregistered with a 3D-rendered image of the brain, on an image-guided surgery system. Seventeen patients underwent the procedure with visual verification of the actual and virtual grids undertaken during the second (postimplantation) surgery. The accuracy of the Virtual Grid electrode positions was further studied in a subgroup of five patients during surgery by plotting the distance from the actual electrode positions by using an infrared stereotactic probe. The accuracy of the Virtual Grid electrode positions by visual in...

We consider a distributed multi-agent network system where the goal is to minimize a sum of convex objective functions of the agents subject to a common convex constraint set. Each agent maintains an iterate sequence and communicates the iterates to its neighbors. Then, each agent combines weighted averages of the received iterates with its own iterate, and adjusts the iterate

Determining a vehicle's lateral position in a highway lane is important for many applicationspreventing runoff the road accidents, determining erratic driving behavior based on vehicle motion, providing feedback to the driver under low visibility conditions, etc. We present a systematic method for quantifying the dynamic performance of Differential GPS, in particular, the Novate1 RT-20 DGPS unit. This is achieved by using an image processing approach. Novatel's RT-20 Double Differencing Carrier Phase Measurement System is specified t o achieve real-time positioning performance of better then 20 cm nominal accuracy. This paper documents the results from a series of dynamic tests carried out on the RT-20 to verify its actual accuracy while on a moving vehicle. The approach adopted here incorporates synchronized data acquisition using two separate computer systems, and experimental verification of the computational latency of the RT-20. The image processing scheme used for this analysis achieved high accuracy by taking advantage of subpixel resolution in the image processing algorithm. Our results indicate that the RT-20 system exhibited a mean error of 2.03 cm in the lateral direction, and 3.16 cm in the longitudinal direction (note that both lateral and longitudinal are with respect to the moving truck) while moving at speeds ranging from 15 mph through 40 mph. The corresponding error standard deviations were 1.98 cm and 34.87 cm respectively. Our main interest is in the lateral positioning performance of the RT-20, which turns out to be very good. Furthermore, we believe that the longitudinal error standard deviation exhibited by the RT-20 can be reduced further by using an algorithm that eliminates the outlier data points.

SUMMARY: The point source recording can be decomposed into a set of plane-wave components with an arbitrary angle of propaga-tion. Such plane wave seismograms have a far simpler structure over spherical waves of the point source records, which makes them ...

In order to test the feasibility of cementum annulations to estimate age in humans, observer error and tooth variability in cementum ring counts were evaluated in a sample of 42 mandibular canine and first premolar pairs. Additionally, two sectioning techniques were evaluated. Demineralized thin sections (7 pm) stained with hematoxylin are the preferred technique since their age related variance is greater than 75% for all tooth types examined. In contrast, less than 50% of the total variance was accounted for among individuals when mineralized sections (80 pm) stained with alizarin red were used. Intertooth variability in ring counts of demineralized sections was large between canines and premolars (43%). Premolars provide counts with lower interobserver error and are the preferred tooth. In a n expanded sample (N = 51) of demineralized premolars, intraobserver and interobserver error accounted for 2% and 5% of the total variance, respectively. Evaluation of several experimental designs showed that increasing the number of slides per tooth has the greatest effect on reducing variance followed by increasing the number of observers. Increasing the number of observations has little effect. Cementum ring counts are measurable to a highly repeatable extent and provide a level of repeatability greater than that reported for the pubic symphysis and auricular surface aging techniques.