Is the optical image of a non-Lambertian fractal surface fractal?

This letter generalizes Pentland's result about the fractal dimension of the optical image of rough natural surfaces, without imposing his requirement that the reflection is Lambertian. Instead, it is assumed that the reflectance coefficient is proportional to the focusing/defocusing due to local surface curvature. It will be proved for this case that the density distribution across the optical image inherits the fractal dimension of the mapped surface

Fractal Metrology for biogeosystems analysis

The solid-pore distribution pattern plays an important role in soil functioning being related with the main physical, chemical and biological multiscale and multitemporal processes of this complex system. In the present research, we studied the aggregation process as self-organizing and operating near a critical point. The structural pattern is extracted from the digital images of three soils (<i>Chernozem, Solonetz</i> and <i>"Chocolate" Clay</i>) and compared in terms of roughness of the gray-intensity distribution quantified by several measurement techniques. Special attention was paid to the uncertainty of each of them measured in terms of standard deviation. Some of the applied methods are known as classical in the fractal context (box-counting, rescaling-range and wavelets analyses, etc.) while the others have been recently developed by our Group. The combination of these techniques, coming from Fractal Geometry, Metrology, Informatics, Probability Theory and Statistics is termed in this paper <i>Fractal Metrology</i> (FM). We show the usefulness of FM for complex systems analysis through a case study of the soil's physical and chemical degradation applying the selected toolbox to describe and compare the structural attributes of three porous media with contrasting structure but similar clay mineralogy dominated by montmorillonites

ATTENUATION CHARACTERISTICS OF SAUDI ARABIAN RESERVOIR SANDSTONE AND LIMESTONE CORES

INTRODUCTION Lithology, porosity, permeability, pore fluids, and effective pressure are some of the important criteria for reservoir characterization. These parameters significantly affect the seismic signature of a reservoir. Thus, establishing correlations between seismic properties on one hand, and lithology, porosity, permeability, and stress on the other, will increase the reliability of reservoir property predictions from seismic measurements. Another advantage of seismic attributes is that they are much easier to measure in-situ than the above mentioned reservoir properties, and since such measurements are noninvasive, an observed correlation between them could also prove useful as an important exploration tool for oil and gas reservoirs. In recent years, with the improvement in borehole sonic sources and receivers, full waveforms are being recorded and processed at the rig site itself. Enough expertise is gained to accurately compute the attenuation quality factors from the full waveforms recorded in the laboratory and borehole sonics. In this paper attenuation quality factors of several Saudi Arabian reservoir sandstone and limestone cores are computed and possible correlation between quality factors and reservoir properties like porosity, permeability, velocities, and wetting state are studied. OBJECTIVE The objective of this paper is to study the pressure dependent behavior of quality factor and to discuss the possible correlation of the seismic attributes like attenuation to the more relevant reservoir characterization properties like porosity, permeability, velocity, and saturation. It has been observed that quality factor Q does not have a good correlation with either porosity or permeability LABORATORY MEASUREMENTS A total of twenty sandstone and limestone reservoir cores have been tested for porosity, permeability, P-and S-wave velocities and quality factors under dry and water saturated conditions. The dried cores were flushed with air, therefore in effect, dry core samples are air saturated dry rocks. Nine simultaneous P-and S-wave measurements were made in the pressure range of 0 -82 MPa. The dry and water saturated P-and S-wave velocities and quality factors were measured on the same core sample. First the measurements on dry core were completed, the core sample was then fully saturated with water and then the Pand S-wave velocities and quality factors were measured on the water saturated core back to contents SCA 2001-57 2 sample under the same confining pressure conditions. Simultaneous Porosity and Permeability measurements in the same pressure range were made on a different sister sample from the same depth. The full wave broadband ultrasonic waves used in this study had a central frequency of 700 KHz. The attenuation quality factors were calculated using spectral ratio method (Toksoz et al., 1979). Correction for diffraction loss due to the finite size of the transducer and the non-planar wavefronts (Papadakis, 1968) were applied using tabulated data of To validate the calculation and diffraction correction procedure for the quality factors, Q, some experiments were performed on French Gres' des Vesges sandstone samples and the results were compared to those available in the literature RESULTS AND DISCUSSION Several investigators In SCA 2001-57 3 CONCLUSIONS • A new parameter, the ratio of P-wave to S-wave quality factors Qp/Qs gives a good correlation to porosity and permeability. • The results presented in this paper confirm the previously published results in literature. • In most of the studies reported in literature, outcrop rocks with emphasis on sandstone were used. Whereas in this paper sandstone and limestone reservoir cores are used. Therefore correlations developed using outcrop samples give a good estimate of reservoir rock properties

An assessment of patient satisfaction for a short-stay program in a physical and rehabilitation medicine day hospital

AbstractIntroductionThe aim of the Physical and Rehabilitation Medicine (PRM) day hospital's short-stay program is to propose a one- or two-day medical and psychosocial assessment to patients with disabilities. The day hospital is run by an interprofessional team, using interdisciplinary cooperation and a hospital/community network.ObjectivesTo describe a tool for assessing patient satisfaction and to present the results of our survey.Patients and methodsA self-administered questionnaire about patient satisfaction was created and given to patients coming to the PRM day hospital. The questionnaire included 27 multiple-choice questions, two visual analogic scales, and one free-response question. The survey was conducted over two months. For the 603 annual day hospital sessions, 143 questionnaires on 143 sessions were filled out.ResultsPatients found the questionnaire easy to use, but a few needed help to fill it out. It permitted us to highlight the places where the short-stay program performed unsatisfactorily.ConclusionsThe self-administered questionnaire seems to be appropriate for assessing patient satisfaction. The highest scores helped to emphasize where the program was functioning correctly, and the lowest scores allowed us to identify the points that needed to be improved

Smoothed particle hydrodynamics (SPH) model for coupled analysis of a damaged ship with internal sloshing in beam seas

The flooding of a damaged ship in waves is a complex process, often coupled with the internal and external liquid motion together with the ship hull motion. Paramount to the operation safety, in order to improve the prediction accuracy of ship motion during the flooding process, the strip theory is applied to study the dynamic response of the damaged ship in beam seas; a smoothed particle hydrodynamics (SPH) model is developed to consider the coupling effects of various factors including internal sloshing of intact cabins and damaged cabins and external waves. The numerical wave tank with a perfectly matched layer absorbing boundary condition is established and validated by the experimental results. The detailed sensitivity study is carried out focusing on the effects of damaged opening sizes, the relative position of opening, and the incident wave and the liquid loading conditions on the dynamic response of the damaged ship in regular beam waves. It is observed that the flooding process was slowed down and interrupted by the water exchanges at the damaged opening due to the dynamic motion. Compared with the opening facing the incident wave, the back one endangered the ship pronouncedly with large amplitude and frequency roll motion. It is also revealed that the liquid tank in the damaged ship imposes a significant influence on its rolling response. It is further demonstrated that the present SPH model is capable of handling the nonlinear phenomenon in a flooding process of a damaged ship

Accessing ns–μs side chain dynamics in ubiquitin with methyl RDCs

This study presents the first application of the model-free analysis (MFA) (Meiler in J Am Chem Soc 123:6098–6107, 2001; Lakomek in J Biomol NMR 34:101–115, 2006) to methyl group RDCs measured in 13 different alignment media in order to describe their supra-τc dynamics in ubiquitin. Our results indicate that methyl groups vary from rigid to very mobile with good correlation to residue type, distance to backbone and solvent exposure, and that considerable additional dynamics are effective at rates slower than the correlation time τc. In fact, the average amplitude of motion expressed in terms of order parameters S2 associated with the supra-τc window brings evidence to the existence of fluctuations contributing as much additional mobility as those already present in the faster ps-ns time scale measured from relaxation data. Comparison to previous results on ubiquitin demonstrates that the RDC-derived order parameters are dominated both by rotameric interconversions and faster libration-type motions around equilibrium positions. They match best with those derived from a combined J-coupling and residual dipolar coupling approach (Chou in J Am Chem Soc 125:8959–8966, 2003) taking backbone motion into account. In order to appreciate the dynamic scale of side chains over the entire protein, the methyl group order parameters are compared to existing dynamic ensembles of ubiquitin. Of those recently published, the broadest one, namely the EROS ensemble (Lange in Science 320:1471–1475, 2008), fits the collection of methyl group order parameters presented here best. Last, we used the MFA-derived averaged spherical harmonics to perform highly-parameterized rotameric searches of the side chains conformation and find expanded rotamer distributions with excellent fit to our data. These rotamer distributions suggest the presence of concerted motions along the side chains