Vegetation cover and radiocarbon dates of palsa and peat plateaus in the Hudson Bay Lowlands

The Holocene development of a treed palsa bog and a peat plateau bog, located near the railroad to Churchill in the Hudson Bay Lowlands of northeastern Manitoba, was traced using peat macrofossil and radiocarbon analyses. Both sites first developed as wet rich fens through paludification of forested uplands around 6800 cal. yr BP. Results show a 20th-century age for the palsa formation and repeated periods of permafrost aggradation and collapse at the peat plateau site during the late Holocene. This timing of permafrost dynamics corroborates well with that inferred from previous studies on other permafrost peatlands in the same region. The developmental history of the palsa and peat plateau bogs is similar to that of adjacent permafrost-free fens, except for the specific frost heave and collapse features associated with permafrost dynamics. Permafrost aggradation and degradation is ascribed to regional climatic, local autogenic and other factors. Particularly the very recent palsa development can be assessed in terms of climatic changes as inferred from meteorological data and surface hydrological changes related to construction of the railroad. The results indicate that cold years with limited snowfall as well as altered drainage patterns associated with infrastructure development may have contributed to the recent palsa formation.

A 18-years long (1993-2011) snow and meteorological dataset from a mid-altitude mountain site (Col de Porte, France, 1325 altitude)

A quality-controlled snow and meteorological dataset spanning the period 1 August 1993-31 July 2011 is presented, originating from the experimental station Col de Porte (1325 m altitude, Chartreuse range, France). Emphasis is placed on meteorological data relevant to the observation and modelling of the seasonal snowpack. In-situ driving data, at the hourly resolution, consist of measurements of air temperature, relative humidity, windspeed, incoming short-wave and long-wave radiation, precipitation rate partitioned between snow- and rainfall, with a focus on the snow-dominated season. Meteorological data for the three summer months (generally from 10 June to 20 September), when the continuity of the field record is not warranted, are taken from a local meteorological reanalysis (SAFRAN), in order to provide a continuous and consistent gap-free record. Data relevant to snowpack properties are provided at the daily (snow depth, snow water equivalent, runoff and albedo) and hourly (snow depth, albedo, runoff, surface temperature, soil temperature) time resolution. Internal snowpack information is provided from weekly manual snowpit observations (mostly consisting in penetration resistance, snow type, snow temperature and density profiles) and from a hourly record of temperature and height of vertically free ''settling'' disks. This dataset has been partially used in the past to assist in developing snowpack models and is presented here comprehensively for the purpose of multi-year model performance assessment. The data is placed on the PANGAEA repository (doi:10.1594/PANGAEA.774249) as well as on the public ftp server ftp://ftp-cnrm.meteo.fr/pub-cencdp/.

Precipitation over sea: Validation against shipboard in-situ measurements

The satellite derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in-situ precipitation measurements from ship rain gauges and optical disdrometers over the open-ocean by applying a statistical analysis for binary forecasts. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the forecast times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the numbers of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, regionally averaged over latitudinal belts, there are deviations between the observed mean precipitation rates and ERA-Interim. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern sub-tropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers it can be concluded that both HOAPS and ERA-Interim are suitable to detect the occurrence of solid precipitation.

Transport costs, distance, and time : evidence from the Japanese Census of Logistics

Geographic distance is a standard proxy for transport costs under the simple assumption that freight fees increase monotonically over space. Using the Japanese Census of Logistics, this paper examines the extent to which transport distance and time affect freight costs across shipping modes, commodity groups, and prefecture pairs. The results show substantial heterogeneity in transport costs and time across shipping modes. Consistent with an iceberg formulation of transport costs, distance has a significantly positive effect on freight costs by air transportation. However, I find the puzzling results that business enterprises are likely to pay more for short-distance shipments by truck, ship, and railroad transportation. As a plausible explanation, I discuss aggregation bias arising from freight-specific premiums for timely, frequent, and small-batch shipments.

Study of the damage evolution of the concrete under freeze-thaw cycles using traditional and non-traditional techniques

Some experiments have been performed to investigate the cyclic freeze-thaw deterioration of concrete, using traditional and non-traditional techniques. Two concrete mixes, with different pore structure, were tested in order to compare the behavior of a freeze-thaw resistant concrete from one that is not. One of the concretes was air entrained, high content of cement and low w/c ratio, and the other one was a lower cement content and higher w/c ratio, without air-entraining agent. Concrete specimens were studied under cyclic freeze-thaw conditions according to UNE-CENT/TS 12390-9 test, using 3% NaCl solution as freezing medium (CDF test: Capillary Suction, De-icing agent and Freeze-thaw Test). The temperature and relative humidity were measured during the cycles inside the specimens using embedded sensors placed at different heights from the surface in contact with the de-icing agent solution. Strain gauges were used to measure the strain variations at the surface of the specimens. Also, measurements of ultrasonic pulse velocity through the concrete specimens were taken before, during, and after the freeze-thaw cycles. According to the CDF test, the failure of the non-air-entraining agent concrete was observed before 28 freeze-thaw cycles; contrariwise, the scaling of the air-entraining agent concrete was only 0.10 kg/m 2 after 28 cycles, versus 3.23 kg/m 2 in the deteriorated concrete, after 28 cycles. Similar behavior was observed on the strain measurements. The residual strain in the deteriorated concrete after 28 cycles was 1150 m versus 65 m, in the air-entraining agent concrete. By means of monitoring the changes of ultrasonic pulse velocity during the freeze-thaw cycles, the deterioration of the tested specimens were assessed

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented.

Significado empírico de la multifractalidad de la precipitación

El objetivo central de la presente investigación es profundizar la interpretación de los parámetros multifractales en el caso de las series de precipitación. Para ello se aborda, en primer lugar, la objetivación de la selección de la parte lineal de las curvas log-log que se encuentra en la base de los métodos de análisis fractal y multifractal; y, en segundo lugar, la generación de series artificiales de precipitación, con características similares a las reales, que permitan manipular los datos y evaluar la influencia de las modificaciones controladas de las series en los resultados de los parámetros multifractales derivados. En cuanto al problema de la selección de la parte lineal de las curvas log-log se desarrollaron dos métodos: a. Cambio de tendencia, que consiste en analizar el cambio de pendiente de las rectas ajustadas a dos subconjuntos consecutivos de los datos. b. Eliminación de casos, que analiza la mejora en el p-valor asociado al coeficiente de correlación al eliminar secuencialmente los puntos finales de la regresión. Los resultados obtenidos respecto a la regresión lineal establecen las siguientes conclusiones: - La metodología estadística de la regresión muestra la dificultad para encontrar el valor de la pendiente de tramos rectos de curvas en el procedimiento base del análisis fractal, indicando que la toma de decisión de los puntos a considerar redunda en diferencias significativas de las pendientes encontradas. - La utilización conjunta de los dos métodos propuestos ayuda a objetivar la toma de decisión sobre la parte lineal de las familias de curvas en el análisis fractal, pero su utilidad sigue dependiendo del número de datos de que se dispone y de las altas significaciones que se obtienen. En cuanto al significado empírico de los parámetros multifratales de la precipitación, se han generado 19 series de precipitación por medio de un simulador de datos diarios en cascada a partir de estimaciones anuales y mensuales, y en base a estadísticos reales de 4 estaciones meteorológicas españolas localizadas en un gradiente de NW a SE. Para todas las series generadas, se calculan los parámetros multifractales siguiendo la técnica de estimación de la DTM (Double Trace Moments - Momentos de Doble Traza) desarrollado por Lavalle et al. (1993) y se observan las modificaciones producidas. Los resultados obtenidos arrojaron las siguientes conclusiones: - La intermitencia, C1, aumenta al concentrar las precipitaciones en menos días, al hacerla más variable, o al incrementar su concentración en los días de máxima, mientras no se ve afectado por la modificación en la variabilidad del número de días de lluvia. - La multifractalidad, α, se ve incrementada con el número de días de lluvia y la variabilidad de la precipitación, tanto anual como mensual, así como también con la concentración de precipitación en el día de máxima. - La singularidad probable máxima, γs, se ve incrementada con la concentración de la lluvia en el día de precipitación máxima mensual y la variabilidad a nivel anual y mensual. - El grado no- conservativo, H, depende del número de los días de lluvia que aparezcan en la serie y secundariamente de la variabilidad general de la lluvia. - El índice de Hurst generalizado se halla muy ligado a la singularidad probable máxima. ABSTRACT The main objective of this research is to interpret the multifractal parameters in the case of precipitation series from an empirical approach. In order to do so the first proposed task was to objectify the selection of the linear part of the log-log curves that is a fundamental step of the fractal and multifractal analysis methods. A second task was to generate precipitation series, with real like features, which allow evaluating the influence of controlled series modifications on the values of the multifractal parameters estimated. Two methods are developed for selecting the linear part of the log-log curves in the fractal and multifractal analysis: A) Tendency change, which means analyzing the change in slope of the fitted lines to two consecutive subsets of data. B) Point elimination, which analyzes the improvement in the p- value associated to the coefficient of correlation when the final regression points are sequentially eliminated. The results indicate the following conclusions: - Statistical methodology of the regression shows the difficulty of finding the slope value of straight sections of curves in the base procedure of the fractal analysis, pointing that the decision on the points to be considered yield significant differences in slopes values. - The simultaneous use of the two proposed methods helps to objectify the decision about the lineal part of a family of curves in fractal analysis, but its usefulness are still depending on the number of data and the statistical significances obtained. Respect to the empiric meaning of the precipitation multifractal parameters, nineteen precipitation series were generated with a daily precipitation simulator derived from year and month estimations and considering statistics from actual data of four Spanish rain gauges located in a gradient from NW to SE. For all generated series the multifractal parameters were estimated following the technique DTM (Double Trace Moments) developed by Lavalle et al. (1993) and the variations produced considered. The results show the following conclusions: 1. The intermittency, C1, increases when precipitation is concentrating for fewer days, making it more variable, or when increasing its concentration on maximum monthly precipitation days, while it is not affected due to the modification in the variability in the number of days it rained. 2. Multifractility, α, increases with the number of rainy days and the variability of the precipitation, yearly as well as monthly, as well as with the concentration of precipitation on the maximum monthly precipitation day. 3. The maximum probable singularity, γs, increases with the concentration of rain on the day of the maximum monthly precipitation and the variability in yearly and monthly level. 4. The non-conservative degree, H’, depends on the number of rainy days that appear on the series and secondly on the general variability of the rain. 5. The general Hurst index is linked to the maximum probable singularity.

Do charges to freight trucks and trains in the European Union reflect their social marginal costs? Application to the case of Spain

In the last few years, the European Union (EU) has become greatly concerned about the environmental costs of road transport in Europe as a result of the constant growth in the market share of trucks and the steady decline in the market share of railroads. In order to reverse this trend, the EU is promoting the implementation of additional charges for heavy goods vehicles (HGV) on the trunk roads of the EU countries. However, the EU policy is being criticised because it does not address the implementation of charges to internalise the external costs produced by automobiles and other transport modes such as railroad. In this paper, we first describe the evolution of the HGV charging policy in the EU, and then assess its practical implementation across different European countries. Second, and of greater significance, by using the case study of Spain, we evaluate to what extent the current fees on trucks and trains reflect their social marginal costs, and consequently lead to an allocative-efficient outcome. We found that for the average case in Spain the truck industry meets more of the marginal social cost produced by it than does the freight railroad industry. The reason for this lies in the large sums of money paid by truck companies in fuel taxes, and the subsidies that continue to be granted by the government to the railroads.

Cobertura de la trinchera ferroviaria de Hendaya

Un problema del ferrocarril al paso por las ciudades europeas es el efecto barrera generado, que impide su desarrollo más allá de las vías. Si se salta la barrera lo cierto es que ello se hace sólo en sitios concretos y el efecto psicológico de aislamiento persiste para los habitantes del entorno. Este trabajo presenta de manera sucinta los problemas de concepción, comprobación y vibraciones planteados por la estructura de cubierta de la trinchera ferroviaria de Hendaya, consistente en una losa de hormigón pretensado y luz variable de 20-40 metros, que resuelve el problema de aislamiento entre las dos partes de la ciudad. Su construcción ha sido posible gracias al acuerdo entre la SNCF e inversores privados y está permitiendo la construcción sobre ella de 6 edificios de viviendas y una residencia de turismo, la demolición del antiguo ?Pont-Vieux? y la construcción de un nuevo ?Pont-Vieux?, integrado completamente en la promoción inmobiliaria. An important problem put by the train in its passage by the cities of Europe generally and in France in particular is the effect barrier which builds up, preventing the cities from developing beyond. Even if this barrier is crossed, it is certain that the passage is restricted to concrete places and always acts as psychological barrier for the local residents. This article presents in a brief way the problems of conception, analysis and vibration of the cover structure of the railroad trench of Hendaye. This structure consists of a 20-40 meters span slab of pre-stressed concrete that solves the isolation problem of both parts of the town of Hendaye. Its construction was possible thanks to the agreement of the SNCF (French Railways)and some private investors, and is allowing the investors the construction on top of 6 residential buildings and a holiday residence, with demolition of the ancient “Pont-Vieux” and building of a new “Pont-Vieux”, which is completely integrated into the real-estate development. Special attention is given to the change of transverse cross-section of the slab during construction stages, which originates a redistribution of stresses, and to the long-term equilibrium of horizontal forces.

Risk assessment of the spanish national railway system

The principal risks in the railway industry are mainly associated with collisions, derailments and level crossing accidents. An understanding of the nature of previous accidents on the railway network is required to identify potential causes and develop safety systems and deploy safety procedures. Risk assessment is a process for determining the risk magnitude to assist with decision-making. We propose a three-step methodology to predict the mean number of fatalities in railway accidents. The first is to predict the mean number of accidents by analyzing generalized linear models and selecting the one that best fits to the available historical data on the basis of goodness-offit statistics. The second is to compute the mean number of fatalities per accident and the third is to estimate the mean number of fatalities. The methodology is illustrated on the Spanish railway system. Statistical models accounting for annual and grouped data for the 1992-2009 time period have been analyzed. After identifying the models for broad and narrow gauges, we predicted mean number of accidents and the number of fatalities for the 2010-18 time period.

Offshore Measurements of Ocean Waves using Stereo Vision Systems

In recent years, remote sensing imaging systems for the measurement of oceanic sea states have attracted renovated attention. Imaging technology is economical, non-invasive and enables a better understanding of the space-time dynamics of ocean waves over an area rather than at selected point locations of previous monitoring methods (buoys, wave gauges, etc.). We present recent progress in space-time measurement of ocean waves using stereo vision systems on offshore platforms, which focus on sea states with wavelengths in the range of 0.01 m to 10 m. Classical epipolar techniques and modern variational methods are reviewed to reconstruct the sea surface from the stereo pairs sequentially in time. The statistical and spectral properties of the resulting observed waves are analyzed. Current improvements of the variational methods are discussed as future lines of research.

Análisis de micromovilidad en vástagos femorales mediante ensayo dinámico de oscilaciones libres

La artroplastia de cadera se considera uno de los mayores avances quirúrgicos de la Medicina. La aplicación de esta técnica de Traumatología se ha incrementado notablemente en los últimos anos, a causa principalmente del progresivo incremento de la esperanza de vida. En efecto, con la edad aumentan los problemas de artrosis y osteoporosis, enfermedades típicas de las articulaciones y de los huesos que requieren en muchos casos la sustitución protésica total o parcial de la articulación. El buen comportamiento funcional de una prótesis depende en gran medida de la estabilidad primaria, es decir, el correcto anclaje de la prótesis en el momento de su implantación. Las prótesis no cementadas basan su éxito a largo plazo en la osteointegración que tiene lugar entre el material protésico y el tejido óseo, y para lograrla es imprescindible conseguir unas buenas condiciones de estabilidad primaria. El aflojamiento aséptico es la principal causa de fallo de artroplastia total de cadera. Este es un fenómeno en el que, debido a complejas interacciones de factores mecánicos y biológicos, se producen movimientos relativos que comprometen la funcionalidad del implante. La minimización de los correspondientes danos depende en gran medida de la detección precoz del aflojamiento. Para lograr la detección temprana del aflojamiento aséptico del vástago femoral se han ensayado diferentes técnicas, tanto in vivo como in vitro: análisis numéricos y técnicas experimentales basadas en sensores de movimientos provocados por cargas transmitidas natural o artificialmente, tales como impactos o vibraciones de distintas frecuencias. Los montajes y procedimientos aplicados son heterogéneos y, en muchas ocasiones, complejos y costosos, no existiendo acuerdo sobre una técnica simple y eficaz de aplicación general. Asimismo, en la normativa vigente que regula las condiciones que debe cumplir una prótesis previamente a su comercialización, no hay ningún apartado referido específicamente a la evaluación de la bondad del diseño del vástago femoral con respecto a la estabilidad primaria. El objetivo de esta tesis es desarrollar una metodología para el análisis, in vitro, de la estabilidad de un vástago femoral implantado, a fin de poder evaluar las técnicas de implantación y los diferentes diseños de prótesis previamente a su oferta en el mercado. Además se plantea como requisito fundamental que el método desarrollado sea sencillo, reversible, repetible, no destructivo, con control riguroso de parámetros (condiciones de contorno de cargas y desplazamientos) y con un sistema de registro e interpretación de resultados rápido, fiable y asequible. Como paso previo, se ha realizado un análisis cualitativo del problema de contacto en la interfaz hueso-vástago aplicando una técnica optomecánica del campo continuo (fotoelasticidad). Para ello se han fabricado tres modelos en 2D del conjunto hueso-vástago, simulando tres tipos de contactos en la interfaz: contacto sin adherencia y con holgura, contacto sin adherencia y sin holgura, y contacto con adherencia y homogéneo. Aplicando la misma carga a cada modelo, y empleando la técnica de congelación de tensiones, se han visualizado los correspondientes estados tensionales, siendo estos más severos en el modelo de unión sin adherencia, como cabía esperar. En todo caso, los resultados son ilustrativos de la complejidad del problema de contacto y confirman la conveniencia y necesidad de la vía experimental para el estudio del problema. Seguidamente se ha planteado un ensayo dinámico de oscilaciones libres con instrumentación de sensores resistivos tipo galga extensométrica. Las muestras de ensayo han sido huesos fémur en todas sus posibles variantes: modelos simplificados, hueso sintético normalizado y hueso de cadáver, seco y fresco. Se ha diseñado un sistema de empotramiento del extremo distal de la muestra (fémur) con control riguroso de las condiciones de anclaje. La oscilación libre de la muestra se ha obtenido mediante la liberación instantánea de una carga estética determinada y aplicada previamente, bien con una maquina de ensayo o bien por gravedad. Cada muestra se ha instrumentado con galgas extensométricas convencionales cuya señal se ha registrado con un equipo dinámico comercial. Se ha aplicado un procedimiento de tratamiento de señal para acotar, filtrar y presentar las respuestas de los sensores en el dominio del tiempo y de la frecuencia. La interpretación de resultados es de tipo comparativo: se aplica el ensayo a una muestra de fémur Intacto que se toma de referencia, y a continuación se repite el ensayo sobre la misma muestra con una prótesis implantada; la comparación de resultados permite establecer conclusiones inmediatas sobre los efectos de la implantación de la prótesis. La implantación ha sido realizada por un cirujano traumatólogo utilizando las mismas técnicas e instrumental empleadas en el quirófano durante la práctica clínica real, y se ha trabajado con tres vástagos femorales comerciales. Con los resultados en el dominio del tiempo y de la frecuencia de las distintas aplicaciones se han establecido conclusiones sobre los siguientes aspectos: Viabilidad de los distintos tipos de muestras sintéticas: modelos simplificados y fémur sintético normalizado. Repetibilidad, linealidad y reversibilidad del ensayo. Congruencia de resultados con los valores teóricos deducidos de la teoría de oscilaciones libres de barras. Efectos de la implantación de tallos femorales en la amplitud de las oscilaciones, amortiguamiento y frecuencias de oscilación. Detección de armónicos asociados a la micromovilidad. La metodología se ha demostrado apta para ser incorporada a la normativa de prótesis, es de aplicación universal y abre vías para el análisis de la detección y caracterización de la micromovilidad de una prótesis frente a las cargas de servicio. ABSTRACT Total hip arthroplasty is considered as one of the greatest surgical advances in medicine. The application of this technique on Traumatology has increased significantly in recent years, mainly due to the progressive increase in life expectancy. In fact, advanced age increases osteoarthritis and osteoporosis problems, which are typical diseases of joints and bones, and in many cases require full or partial prosthetic replacement on the joint. Right functional behavior of prosthesis is highly dependent on the primary stability; this means it depends on the correct anchoring of the prosthesis at the time of implantation. Uncemented prosthesis base their long-term success on the quality of osseointegration that takes place between the prosthetic material and bone tissue, and to achieve this good primary stability conditions is mandatory. Aseptic loosening is the main cause of failure in total hip arthroplasty. This is a phenomenon in which relative movements occur, due to complex interactions of mechanical and biological factors, and these micromovements put the implant functionality at risk. To minimize possible damage, it greatly depends on the early detection of loosening. For this purpose, various techniques have been tested both in vivo and in vitro: numerical analysis and experimental techniques based on sensors for movements caused by naturally or artificially transmitted loads, such as impacts or vibrations at different frequencies. The assemblies and methods applied are heterogeneous and, in many cases, they are complex and expensive, with no agreement on the use of a simple and effective technique for general purposes. Likewise, in current regulations for governing the conditions to be fulfilled by the prosthesis before going to market, there is no specific section related to the evaluation of the femoral stem design in relation to primary stability. The aim of this thesis is to develop a in vitro methodology for analyzing the stability of an implanted femoral stem, in order to assess the implantation techniques and the different prosthesis designs prior to its offer in the market. We also propose as a fundamental requirement that the developed testing method should be simple, reversible, repeatable, non-destructive, with close monitoring of parameters (boundary conditions of loads and displacements) and with the availability of a register system to record and interpret results in a fast, reliable and affordable manner. As a preliminary step, we have performed a qualitative analysis of the contact problems in the bone-stem interface, through the application of a continuous field optomechanical technique (photoelasticity). For this proposal three 2D models of bone–stem set, has been built simulating three interface contact types: loosened an unbounded contact, unbounded and fixed contact, and bounded homogeneous contact. By means of applying the same load to each model, and using the stress freezing technique, it has displayed the corresponding stress states, being more severe as expected, in the unbounded union model. In any case, the results clearly show the complexity of the interface contact problem, and they confirm the need for experimental studies about this problem. Afterward a free oscillation dynamic test has been done using resistive strain gauge sensors. Test samples have been femur bones in all possible variants: simplified models, standardized synthetic bone, and dry and cool cadaveric bones. An embedding system at the distal end of the sample with strong control of the anchoring conditions has been designed. The free oscillation of the sample has been obtained by the instantaneous release of a static load, which was previously determined and applied to the sample through a testing machine or using the gravity force. Each sample was equipped with conventional strain gauges whose signal is registered with a marketed dynamic equipment. Then, it has applied a signal processing procedure to delimit, filter and present the time and frequency response signals from the sensors. Results are interpreted by comparing different trials: the test is applied to an intact femur sample which is taken as a reference, and then this test is repeated over the same sample with an implanted prosthesis. From comparison between results, immediate conclusions about the effects of the implantation of the prosthesis can be obtained. It must be said that the implementation has been made by an expert orthopedic surgeon using the same techniques and instruments as those used in clinical surgery. He has worked with three commercial femoral stems. From the results obtained in the time and frequency domains for the different applications the following conclusions have been established: Feasibility of the different types of synthetic samples: simplified models and standardized synthetic femur. Repeatability, linearity and reversibility of the testing method. Consistency of results with theoretical values deduced from the bars free oscillations theory. Effects of introduction of femoral stems in the amplitude, damping and frequencies of oscillations Detection of micromobility associated harmonics. This methodology has been proved suitable to be included in the standardization process of arthroplasty prosthesis, it is universally applicable and it allows establishing new methods for the analysis, detection and characterization of prosthesis micromobility due to functional loads.

Offshore remote sensing of the ocean by stereo vision systems

In recent years, remote sensing imaging systems for the measurement of oceanic sea states have attracted renovated attention. Imaging technology is economical, non-invasive and enables a better understanding of the space-time dynamics of ocean waves over an area rather than at selected point locations of previous monitoring methods (buoys, wave gauges, etc.). We present recent progress in space-time measurement of ocean waves using stereo vision systems on offshore platforms, which focus on sea states with wavelengths in the range of 0.01 m to 1 m. Both traditional disparity-based systems and modern elevation-based ones are presented in a variational optimization framework: the main idea is to pose the stereoscopic reconstruction problem of the surface of the ocean in a variational setting and design an energy functional whose minimizer is the desired temporal sequence of wave heights. The functional combines photometric observations as well as spatial and temporal smoothness priors. Disparity methods estimate the disparity between images as an intermediate step toward retrieving the depth of the waves with respect to the cameras, whereas elevation methods estimate the ocean surface displacements directly in 3-D space. Both techniques are used to measure ocean waves from real data collected at offshore platforms in the Black Sea (Crimean Peninsula, Ukraine) and the Northern Adriatic Sea (Venice coast, Italy). Then, the statistical and spectral properties of the resulting observed waves are analyzed. We show the advantages and disadvantages of the presented stereo vision systems and discuss future lines of research to improve their performance in critical issues such as the robustness of the camera calibration in spite of undesired variations of the camera parameters or the processing time that it takes to retrieve ocean wave measurements from the stereo videos, which are very large datasets that need to be processed efficiently to be of practical usage. Multiresolution and short-time approaches would improve efficiency and scalability of the techniques so that wave displacements are obtained in feasible times.

Space-time ocean wave measurement using variational stereo vision systems

Remote sensing imaging systems for the measurement of oceanic sea states have recently attracted renovated attention. Imaging technology is economical, non-invasive and enables a better understanding of the space-time dynamics of ocean waves over an area rather than at selected point locations of previous monitoring methods (buoys, wave gauges, etc.). We present recent progress in space-time measurement of ocean waves using stereo vision systems on offshore platforms. Both traditional disparity-based systems and modern elevation-based ones are presented in a variational optimization framework: the main idea is to pose the stereoscopic reconstruction problem of the surface of the ocean in a variational setting and design an energy functional whose minimizer is the desired temporal sequence of wave heights. The functional combines photometric observations as well as spatial and temporal smoothness priors. Disparity methods estimate the disparity between images as an intermediate step toward retrieving the depth of the waves with respect to the cameras, whereas elevation methods estimate the ocean surface displacements directly in 3-D space. Both techniques are used to measure ocean waves from real data collected at offshore platforms in the Black Sea (Crimean Peninsula, Ukraine) and the Northern Adriatic Sea (Venice coast, Italy). Then, the statistical and spectral properties of the resulting observed waves are analyzed. We show the advantages and disadvantages of the presented stereo vision systems and discuss the improvement of their performance in critical issues such as the robustness of the camera calibration in spite of undesired variations of the camera parameters.