Reduction of truncation errors in planar, cylindrical and partial spherical near-field antenna measurements

A method to reduce truncation errors in near-field antenna measurements is presented. The method is based on the Gerchberg-Papoulis iterative algorithm used to extrapolate band-limited functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward hemisphere. The extension of the valid region is achieved by the iterative application of a transformation between two different domains. After each transformation, a filtering process that is based on known information at each domain is applied. The first domain is the spectral domain in which the plane wave spectrum (PWS) is reliable only within a known region. The second domain is the field distribution over the antenna under test (AUT) plane in which the desired field is assumed to be concentrated on the antenna aperture. The method can be applied to any scanning geometry, but in this paper, only the planar, cylindrical, and partial spherical near-field measurements are considered. Several simulation and measurement examples are presented to verify the effectiveness of the method.

Correction of systematic errors in Wide Area Multilateration

This work presents a method to estimate and correct slow time-dependent position errors due to non perfect ground station synchronization and tropospheric propagation. It uses opportunity traffic emissions, i.e. signals transmitted from the aircrafts within the coverage zone. This method is used to overcome the difficulty of installing reference beacons simultaneously visible by all the base stations in a given Wide Area Multilateration (WAM) system.

A New Method to Reduce Truncation Errors in Partial Spherical Near-Field Measurements

A new and effective method for reduction of truncation errors in partial spherical near-field (SNF) measurements is proposed. The method is useful when measuring electrically large antennas, where the measurement time with the classical SNF technique is prohibitively long and an acquisition over the whole spherical surface is not practical. Therefore, to reduce the data acquisition time, partial sphere measurement is usually made, taking samples over a portion of the spherical surface in the direction of the main beam. But in this case, the radiation pattern is not known outside the measured angular sector as well as a truncation error is present in the calculated far-field pattern within this sector. The method is based on the Gerchberg-Papoulis algorithm used to extrapolate functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward hemisphere. To verify the effectiveness of the method, several examples are presented using both simulated and measured truncated near-field data.

New methods to reduce leakage errors in planar near-field measurements

This paper describes two methods to cancel the effect of two kinds of leakage signals which may be presented when an antenna is measured in a planar near-field range. One method tries to reduce leakage bias errors from the receiver¿s quadrature detector and it is based on estimating the bias constant added to every near-field data sample. Then, that constant is subtracted from the data, removing its undesired effect on the far-field pattern. The estimation is performed by back-propagating the field from the scan plane to the antenna under test plane (AUT) and averaging all the data located outside the AUT aperture. The second method is able to cancel the effect of the leakage from faulty transmission lines, connectors or rotary joints. The basis of this method is also a reconstruction process to determine the field distribution on the AUT plane. Once this distribution is known, a spatial filtering is applied to cancel the contribution due to those faulty elements. After that, a near-field-to-far-field transformation is applied, obtaining a new radiation pattern where the leakage effects have disappeared. To verify the effectiveness of both methods, several examples are presented.

Subjective Evaluation of Transmission Errors in IPTV and 3DTV

The increase of multimedia services delivered over packet-based networks has entailed greater quality expectations of the end-users. This has led to an intensive research on techniques for evaluating the quality of experience perceived by the viewers of audiovisual content, considering the different degradations that it could suffer along the broadcasting system. In this paper, a comprehensive study of the impact of transmission errors affecting video and audio in IPTV is presented. With this aim, subjective assessment tests were carried out proposing a novel methodology trying to keep as close as possible home environment viewing conditions. Also 3DTV content in side-by-side format has been used in the experiments to compare the impact of the degradations. The results provide a better understanding of the effects of transmission errors, and show that the QoE related to the first approach of 3DTV is acceptable, but the visual discomfort that it causes should be reduced.

Subjective assessment of the impact of transmission errors in 3DTV compared to HDTV

Recently, broadcasted 3D video content has reached households with the first generation of 3DTV. However, few studies have been done to analyze the Quality of Experience (QoE) perceived by the end-users in this scenario. This paper studies the impact of trans- mission errors in 3DTV, considering that the video is delivered in side-by-side format over a conventional packet-based network. For this purpose, a novel evaluation methodology based on standard sin- gle stimulus methods and with the aim of keeping as close as pos- sible the home environment viewing conditions has been proposed. The effects of packet losses in monoscopic and stereoscopic videos are compared from the results of subjective assessment tests. Other aspects were also measured concerning 3D content as naturalness, sense of presence and visual fatigue. The results show that although the final perceived QoE is acceptable, some errors cause important binocular rivalry, and therefore, substantial visual discomfort.

Validation of microsatellite markers for cytotype discrimination in the model grass Brachypodium distachyon

Brachypodium distachyon (2n = 2x = 10) is a small annual grass species where the existence of three different cytotypes (10, 20 and 30 chromosomes) has long been regarded as a case of autopolyploid series, with x = 5. However, it has been demonstrated that the cytotypes assumed to be polyploids represent two separate Brachypodium species recently named as B. stacei (2n = 2x = 20) and B. hybridum (2n = 4x = 30). The aim of this study was to find a PCR-based alternative approach that could replace standard cytotyping methods (i. e., chromosome counting and flow cytometry) to characterize each of the three Brachypodium species. We have analyzed with four microsatellite (SSR) markers eighty-three Brachypodium distachyon-type lines from varied locations in Spain, including the Balearic and Canary Islands. Within this set of lines, 64, 4 and 15 had 10, 20 and 30 chromosomes, respectively. The surveyed markers produced cytotype-specific SSR profiles. So, a single amplification product was generated in the diploid samples, with non-overlapping allelic ranges between the 2n = 10 and 2n = 20 cytotypes, whereas two bands, one in the size range of each of the diploid cytotypes, were amplified in the 2n = 30 lines. Furthermore, the remarkable size difference obtained with the SSR ALB165 allowed the identification of the Brachypodium species by simple agarose gel electrophoresis.

Hexagonal patterns in a model for rotating convection

We study a model equation that mimics convection under rotation in a fluid with temperature- dependent properties (non-Boussinesq (NB)), high Prandtl number and idealized boundary conditions. It is based on a model equation proposed by Segel [1965] by adding rotation terms that lead to a Kuppers-Lortz instability [Kuppers & Lortz, 1969] and can develop into oscillating hexagons. We perform a weakly nonlinear analysis to find out explicitly the coefficients in the amplitude equation as functions of the rotation rate. These equations describe hexagons and os- cillating hexagons quite well, and include the Busse?Heikes (BH) model [Busse & Heikes, 1980] as a particular case. The sideband instabilities as well as short wavelength instabilities of such hexagonal patterns are discussed and the threshold for oscillating hexagons is determined.

Including functional usability features in a Model-Driven Development Method

The Software Engineering (SE) community has historically focused on working with models to represent functionality and persistence, pushing interaction modelling into the background, which has been covered by the Human Computer Interaction (HCI) community. Recently, adequately modelling interaction, and specifically usability, is being considered as a key factor for success in user acceptance, making the integration of the SE and HCI communities more necessary. If we focus on the Model-Driven Development (MDD) paradigm, we notice that there is a lack of proposals to deal with usability features from the very first steps of software development process. In general, usability features are manually implemented once the code has been generated from models. This contradicts the MDD paradigm, which claims that all the analysts? effort must be focused on building models, and the code generation is relegated to model to code transformations. Moreover, usability features related to functionality may involve important changes in the system architecture if they are not considered from the early steps. We state that these usability features related to functionality can be represented abstractly in a conceptual model, and their implementation can be carried out automatically.

Influencia del viento en los ensayos de rebase en modelo físico a escala reducida = Wind effect on wave overtopping in physical model test

El artículo que se presenta a continuación recoge la ampliación de una investigación previa sobre los rebases en los espaldones de los diques verticales y en talud. Para ello se han realizado una serie de ensayos en modelo físico a escala reducida sobre la sección vertical del Dique de Levante de Málaga, cuyo objeto principal fue analizar el efecto del viento en el rebase. Los ensayos se han realizado generando oleaje con y sin viento, comparando los resultados obtenidos en cada una de las dos situaciones y se han llevado a cabo en el Canal de Oleaje y Viento de Gran Escala existente en el Laboratorio de Experimentación Marítima del Centro de Estudios de Puertos y Costas del CEDEX. The purpose of the research work as summarised in this article, resulting from diverse work carried out at the CEDEX, is to make an analysis of the influence of wind effects on the wave overtopping of vertical sea-walls. The results obtained in the Málaga´s Levante breakwater tests are presented here. The test was carried out in large sized facilities where waves and wind are generated.

The interurban DRAG-Spain model: the main factors of influence on road accidents in Spain

This paper presents the results of applying DRAG methodology to the identification of the main factors of influence on the number of injury and fatal accidents occurring on Spain’s interurban network. Nineteen independent variables have been included in the model grouped together under ten categories: exposure, infrastructure, weather, drivers, economic variables, vehicle stock, surveillance, speed and legislative measures. Highly interesting conclusions can be reached from the results on the basis of the different effects of a single variable on each of the accident types according to severity. The greatest influence revealed by the results is exposure, which together with inexperienced drivers, speed and an ageing vehicle stock, have a negative effect, while the increased surveillance on roads, the improvement in the technological features of vehicles and the proportion of high capacity networks have a positive effect, since the results obtained show a significant drop in accidents.

Regularized model learning in EDAs for continuous and multi-objective optimization

Probabilistic modeling is the de�ning characteristic of estimation of distribution algorithms (EDAs) which determines their behavior and performance in optimization. Regularization is a well-known statistical technique used for obtaining an improved model by reducing the generalization error of estimation, especially in high-dimensional problems. `1-regularization is a type of this technique with the appealing variable selection property which results in sparse model estimations. In this thesis, we study the use of regularization techniques for model learning in EDAs. Several methods for regularized model estimation in continuous domains based on a Gaussian distribution assumption are presented, and analyzed from di�erent aspects when used for optimization in a high-dimensional setting, where the population size of EDA has a logarithmic scale with respect to the number of variables. The optimization results obtained for a number of continuous problems with an increasing number of variables show that the proposed EDA based on regularized model estimation performs a more robust optimization, and is able to achieve signi�cantly better results for larger dimensions than other Gaussian-based EDAs. We also propose a method for learning a marginally factorized Gaussian Markov random �eld model using regularization techniques and a clustering algorithm. The experimental results show notable optimization performance on continuous additively decomposable problems when using this model estimation method. Our study also covers multi-objective optimization and we propose joint probabilistic modeling of variables and objectives in EDAs based on Bayesian networks, speci�cally models inspired from multi-dimensional Bayesian network classi�ers. It is shown that with this approach to modeling, two new types of relationships are encoded in the estimated models in addition to the variable relationships captured in other EDAs: objectivevariable and objective-objective relationships. An extensive experimental study shows the e�ectiveness of this approach for multi- and many-objective optimization. With the proposed joint variable-objective modeling, in addition to the Pareto set approximation, the algorithm is also able to obtain an estimation of the multi-objective problem structure. Finally, the study of multi-objective optimization based on joint probabilistic modeling is extended to noisy domains, where the noise in objective values is represented by intervals. A new version of the Pareto dominance relation for ordering the solutions in these problems, namely �-degree Pareto dominance, is introduced and its properties are analyzed. We show that the ranking methods based on this dominance relation can result in competitive performance of EDAs with respect to the quality of the approximated Pareto sets. This dominance relation is then used together with a method for joint probabilistic modeling based on `1-regularization for multi-objective feature subset selection in classi�cation, where six di�erent measures of accuracy are considered as objectives with interval values. The individual assessment of the proposed joint probabilistic modeling and solution ranking methods on datasets with small-medium dimensionality, when using two di�erent Bayesian classi�ers, shows that comparable or better Pareto sets of feature subsets are approximated in comparison to standard methods.

A method for Kinematic Calibration of a Parallel Robot by using one camera in hand and a spherical object

The main purpose of robot calibration is the correction of the possible errors in the robot parameters. This paper presents a method for a kinematic calibration of a parallel robot that is equipped with one camera in hand. In order to preserve the mechanical configuration of the robot, the camera is utilized to acquire incremental positions of the end effector from a spherical object that is fixed in the word reference frame. The positions of the end effector are related to incremental positions of resolvers of the motors of the robot, and a kinematic model of the robot is used to find a new group of parameters which minimizes errors in the kinematic equations. Additionally, properties of the spherical object and intrinsic camera parameters are utilized to model the projection of the object in the image and improving spatial measurements. Finally, the robotic system is designed to carry out tracking tasks and the calibration of the robot is validated by means of integrating the errors of the visual controller.

Tomas Lopez's Geographic Atlas of Spain in the Peninsular War: A methodology for determining errors

During the Peninsular War, Napoleon's and Wellington's armies were aware of the lack of precision in the maps of Spain and its provinces that appeared in Tomas Lopez \s Geographical Atlas of Spain. The errors were due to the non-topographical surveying method he used which he had learned from his teacher Jean Baptiste Bourguignon D 'Anville. To map all of the Spanish provinces, Tomas Lopez divided them into circles of three leagues in diameter (16,718 m), taking a particular town as the centre. He asked the town's priest to draw a map of the territory and to complete a questionnaire that Tomas Lopez sent to him. The priest was to return the two documents after he had completed them. Subsequently, at his desk, Tomas Lopez used the maps and reports as well as other graphic and written sources from various locations to make an outline of each map. Next, he made a mosaic that served as a pattern for drawing the final provincial map. We will see the way that this method was applied in two concrete cases: the villages ofChavaler and Monteagudo, situated in the Spanish province of Soria, and verify their degree of accuracy. We will use the maps drawn by the priests in 1767, the final map of the province which was published in 1804 by Tomás López, and a current map of the province showing the angular and linear errors in Lopez \s map.

Analytic model of a cache-only memory architecture

An approximate analytic model of a shared memory multiprocessor with a Cache Only Memory Architecture (COMA), the busbased Data Difussion Machine (DDM), is presented and validated. It describes the timing and interference in the system as a function of the hardware, the protocols, the topology and the workload. Model results have been compared to results from an independent simulator. The comparison shows good model accuracy specially for non-saturated systems, where the errors in response times and device utilizations are independent of the number of processors and remain below 10% in 90% of the simulations. Therefore, the model can be used as an average performance prediction tool that avoids expensive simulations in the design of systems with many processors.