Rigid body motion in viscous flows using the Finite Element Method

A new model for the numerical simulation of a rigid body moving in a viscous fluid flow using FEM is presented. One of the most interesting features of this approach is the small computational effort required to solve the motion of the rigid body, comparable to a pure fluid solver. The model is based on the idea of extending the fluid velocity inside the rigid body and solving the flow equations with a penalization term to enforce rigid motion inside the solid. In order to get the velocity field in the fluid domain the Navier-Stokes equations for an incompressible viscous flow are solved using a fractional-step procedure combined with the two-step Taylor-Galerkin for the fractional linear momentum. Once the velocity field in the fluid domain is computed, calculation of the rigid motion is obtained by averaging translation and angular velocities over the solid. One of the main challenges when dealing with the fluid-solid interaction is the proper modelling of the interface which separates the solid moving mass from the viscous fluid. In this work the combination of the level set technique and the two-step Taylor-Galerkin algorithm for tracking the fluid-solid interface is proposed. The good properties exhibited by the two-step Taylor-Galerkin, minimizing oscillations and numerical diffusion, make this method suitable to accurately advect the solid domain avoiding distortions at its boundaries, and thus preserving the initial size and shape of the rigid body. The proposed model has been validated against empirical solutions, experimental data and numerical simulations found in the literature. In all tested cases, the numerical results have shown to be accurate, proving the potential of the proposed model as a valuable tool for the numerical analysis of the fluid-solid interaction.Comment: Research article; 41 pages, 40 figures, 5 tables, 91 reference

Transformations due to mylonitization processes in granitic rocks

[Resumen] El objetivo de este estudio es determinar las transformaciones, tanto a nivel mineralógico como textural, experimentadas por rocas graníticas tardihercínicas afectadas por procesos de milonitización en el sector oriental de la Sierra de Gredos (Sistema Central Español). De igual modQ se intenta determinar la influencia de dichas transformaciones en la composición química de las rocas milonitizadas . El incremento progresivo de la deformación provoca una serie de transformaciones texturales en las que a partir de granitoides de grano grueso porfídicos se generan unas milonitas porfidoclásticas planolineares en el núcleo de la banda de fractura. Desde el punto de vista mineralógico se aprecia una total trituración y degradación de la biotita, que se transforma a clorita de grano muy fino dispersa en la matriz milonítica. También se observan ciertas removilizaciones de feldespato potásico y albita y reajustes metamórficos de bajo grado (en facies de esquistos verdes). Los cambios composicionales acompañantes consisten en un enriquecimiento en Si02, CaO y Na20 en la zona de máxima milonitización y un empobrecimiento en K20 y P20 S en el mismo sentido. En cuanto a los elementos traza, tan sólo Rb y Sr muestran un ligero empobrecimiento en la zona milonítica.[Abstract] The aim of this paper is the determination of the textural and mineralogical transformations introduced in late-Hercynian granitic rocks which have undergone mylonitization processes in the Eastern Sierra de Gredos (Spanish Central System). It also is intended to determine the influence of such changes on the chemical composition of the mylonitic rocks. The progressive increasing of strain causes a series of textural transformations in the originally porphyritic, coarse-grained granitoids leading to formation of porphyroclastic mylonitic rocks with development of planelinear fabrics at the core of the fracture zone. From a mineralogical point of view, transformation~ consist in entire crushing and degradation of biotite, which converts into very fine-grained chlorite disseminated within the mylonitic matrix. Likewise, K-feldspar and albite remobilizations and low grade (greenschists facies) metamorphic readjustments can be observed. The accompanying compositional changes are Si02, CaO and Na20 enrichment and K20 and P20S impoverishment towards the zone of maximum mylonitization. Concerning the trace elements, only Rb and Sr show a weak impoverishment within the mylonitic zone

Non-Destructive Global and Localized 2D T1/T2 NMR Relaxometry to Resolve Microstructure in Apples Affected by Watercore

Apples can be considered as having a complex system formed by several structures at different organization levels: macroscale (>100 μm) and microscale (>100 μm) and microscale (<100 μm). This work implements 2D T1/T2 global and localized relaxometry sequences on whole apples to be able to perform an intensive non-destructive and non-invasive microstructure study. The 2D T1/T2 cross-correlation spectroscopy allows the extraction of quantitative information about the water compartmentation in different subcellular organelles. A clear difference is found as sound apples show neat peaks for water in different subcellular compartments, such as vacuolar, cytoplasmatic and extracellular water, while in watercore-affected tissues such compartments appear merged. Localized relaxometry allows for the predefinition of slices in order to understand the microstructure of a particular region of the fruit, providing information that cannot be derived from global 2D T1/T2 relaxometry

MRI texture analysis as means for addressing rehydration and milk diffusion in cereals

Cereals microstructure is one of the primary quality attributes of cereals. Cereals rehydration and milk diffusion depends on such microstructure and thus, the crispiness and the texture, which will make it more palatable for the final consumer. Magnetic Resonance Imaging (MRI) is a very powerful tomographic tool since acquisition parameter leads to a wide possibility for identifying textures, structures and liquids mobility. It is suited for noninvasive imaging of water and fats. Rehydration and diffusion cereals processes were measured by MRI at different times and using two different kinds of milk, varying their fat level. Several images were obtained. A combination of textural analysis (based on the analysis of histograms) and segmentation methods (in order to understand the rehydration level of each variety of cereals) were performed. According to the rehydration level, no advisable clustering behaviour was found. Nevertheless, some differences were noticeable between the coating, the type of milk and the variety of cereals

Reforma beneficial en Palencia a fines del Antiguo Régimen

La reforma beneficial es el intento por parte de la Corona de mejorar aquella parte de los bienes del clero que estaban vinculados a cargos u organismos eclesiásticos, pertenecían a la Iglesia como institución y la participación de sus miembros se producía como contraprestación al desempeño de unas funciones. Había una gran diferencia entre parroquias e incluso dentro de ellas. Estos objetivos hay que enmarcarlos dentro de la política reformista e ilustrada que se realizó durante el reinado de Carlos III

Optimization of Planck/LFI on--board data handling

To asses stability against 1/f noise, the Low Frequency Instrument (LFI) onboard the Planck mission will acquire data at a rate much higher than the data rate allowed by its telemetry bandwith of 35.5 kbps. The data are processed by an onboard pipeline, followed onground by a reversing step. This paper illustrates the LFI scientific onboard processing to fit the allowed datarate. This is a lossy process tuned by using a set of 5 parameters Naver, r1, r2, q, O for each of the 44 LFI detectors. The paper quantifies the level of distortion introduced by the onboard processing, EpsilonQ, as a function of these parameters. It describes the method of optimizing the onboard processing chain. The tuning procedure is based on a optimization algorithm applied to unprocessed and uncompressed raw data provided either by simulations, prelaunch tests or data taken from LFI operating in diagnostic mode. All the needed optimization steps are performed by an automated tool, OCA2, which ends with optimized parameters and produces a set of statistical indicators, among them the compression rate Cr and EpsilonQ. For Planck/LFI the requirements are Cr = 2.4 and EpsilonQ <= 10% of the rms of the instrumental white noise. To speedup the process an analytical model is developed that is able to extract most of the relevant information on EpsilonQ and Cr as a function of the signal statistics and the processing parameters. This model will be of interest for the instrument data analysis. The method was applied during ground tests when the instrument was operating in conditions representative of flight. Optimized parameters were obtained and the performance has been verified, the required data rate of 35.5 Kbps has been achieved while keeping EpsilonQ at a level of 3.8% of white noise rms well within the requirements.Comment: 51 pages, 13 fig.s, 3 tables, pdflatex, needs JINST.csl, graphicx, txfonts, rotating; Issue 1.0 10 nov 2009; Sub. to JINST 23Jun09, Accepted 10Nov09, Pub.: 29Dec09; This is a preprint, not the final versio

1H HR MAS NMR metabolomic and non-destructive 2D NMR relaxometry to assess internal quality in apples.

NMR can be considered a multi-scale multidimensional technology in the sense that it provides both spatial insight at macroscopic (MRI) or microscopic level (relaxometry), together with chemical characterization (HR-MAS). In this study 296 apples (from 4 cultivars) were MRI screened (20 slices per fruit) among which 7 fruits were used for metabolomic study by 1H HR MAS in order to assess various chemical shifts: malic acid, sucrose, glucose, fructose and ethanol. On the first season, tissue samples were taken from the sound and affected apples (near the core, centre and outer part of the mesocarp) belonging to sound and affected locations, while on the second season, tissue samples were focused on the comparison between sound and affected tissue. Beside, MRI and 2D non-destructive relaxometry (on whole fruits, and localized tissue) where performed on 72 and 12 apples respectively in order to compare features at macroscopic (tissue) and microscopic (subcellular) level. HR MAS shows higher content of ?-glucose, ?-glucose, malic acid and aromatic compounds in watercore affected tissues from both seasons, while sound tissue reflects higher sucrose. Microscopic (subcellular) degradation of tissue varies according to disorder development and is in good accordance with macroscopic characterization with MRI

Validation of a gas chromatography-mass spectrometry method for the analysis of sterol oxidation products in serum

A validated gas chromatography-mass spectrometry (GC-MS) detection method for the quantitative analysis of sterol oxidation products (SOPs) in serum is described. After a lipid extraction procedure with chloroform-methanol, a cold saponification and purification by solid phase extraction, oxysterols were derivatized to form trimethyl-sylil-ethers which were subjected to GC-MS analysis. Calibration curves for cholesterol oxidation products showed determination coefficient (R(2)) of 1.0, with low values for the coefficient of variation of the response factors (< 1%). Detection and quantification limits were below 5 ng/mL and 10 ng/mL, respectively. Recovery data were between 77.65% and 110.29% (CV < 10% for all compounds). Good results were obtained for within- and between-day repeatability, with values below 10%. In conclusion, the method performed is suitable for the determination and quantification of SOPs in serum