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Nath, Fred y Sam Galbraith. "The effect of mannitol on cerebral white matter water content". Journal of Neurosurgery 65, n.º 1 (julio de 1986): 41–43. http://dx.doi.org/10.3171/jns.1986.65.1.0041.
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✓ The authors have studied the effect of a low-dose (0.28 gm/kg) bolus infusion of mannitol on brain water in man. In eight patients with severe head injury, small pieces of subcortical white matter were taken at craniotomy both before and after infusion of mannitol. The tissue specific gravity was measured using a graduated specific-gravity column, and from it the brain water content was calculated. White matter specific gravity rose from a mean (± standard error of the mean) of 1.0325 ± 0.0012 before mannitol infusion to 1.0352 ± 0.0011 after mannitol administration, and the brain water content fell from a mean of 80.94% ± 2.5% to 75.28% ± 2.3%. The differences were significant (p < 0.01). This study shows that, after head injury in man, mannitol increases the white matter specific gravity and probably does so by reducing brain water.
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Y., Mr Deokate A., Prof Mundhe V. L. y Dr N. G. Narve. "Critical Time –Motion and Economic Analysis of Linear and Rotary Gravity Conveyor for application One man multi-machine setup as low cost automation in material handling". International Journal of Trend in Scientific Research and Development Volume-2, Issue-3 (30 de abril de 2018): 489–96. http://dx.doi.org/10.31142/ijtsrd10961.
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ANTONIADIS, I. "POSSIBLE LOW ENERGY MANIFESTATIONS OF STRINGS AND GRAVITY". International Journal of Modern Physics D 19, n.º 08n10 (agosto de 2010): 1339–50. http://dx.doi.org/10.1142/s0218271810017536.
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Lowering the string scale in the TeV region provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter region, and transverse to a braneworld where our universe must be confined. The author reviews the main properties of this scenario and its implications for observations at both particle colliders, and in non-accelerator gravity experiments.
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Wardenaar, Floris, Carmen P. Ortega-Santos, Kaila Vento, Stephanie Olzinski, Jason Olig, Stavros Kavouras y Carol Johnston. "Reliability of 3 Urine Specific Gravity Meters for Measuring Brix and Urine Solutions at Different Temperatures". Journal of Athletic Training 56, n.º 4 (31 de marzo de 2021): 389–95. http://dx.doi.org/10.4085/1062-6050-0142.20.
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Context Urine specific gravity (USG) should be measured at room temperature (20°C), but the temperature of the sample is not always considered. Objective To evaluate the effect of sample temperature on the measurement accuracy of a digital refractometer (DIG), manual optical refractometer (MAN), and hydrometer (HYD). Design Descriptive laboratory study. Main Outcome Measure(s) Urine specific gravity. Results Experiment 1 (24 Brix (°Bx) samples) showed that measurements via the DIG and MAN did not differ from the reference, but HYD provided lower or inconsistent values compared with °Bx and was highly correlated with °Bx solutions (r, > = 0.89). The overall diagnostic ability of elevated USG cut-off values (≥1.020, ≥1.025, ≥1.030) was high for all tools (area under the curve >0.92). Misclassification of samples increased from 0 to 2 at 1.020 to 1 to 3 samples at cutoffs of 1.025 and 1.030 USG. Bland-Altman analysis showed that the DIG 5°C underreported slightly without reporting bias (r = −0.344, P = .13); all other plots for the DIG, MAN, and HYD showed considerably larger underreporting at higher concentrations (r = −0.21 to −0.97 with P >.02) at all temperatures. The outcomes of experiment 2 (33 fresh urine samples) using DIG 20°C as the standard demonstrated only negligible differences between the DIG and MAN at all temperatures but larger differences using the HYD. Conclusions All tools showed reporting bias compared with the °Bx solutions, which can affect the classification of low and high urine concentration at higher USG cutoff values, especially with a sample temperature of 37°C.
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Hauk, Markus y Roland Pail. "Gravity Field Recovery Using High-Precision, High–Low Inter-Satellite Links". Remote Sensing 11, n.º 5 (5 de marzo de 2019): 537. http://dx.doi.org/10.3390/rs11050537.
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Past temporal gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE), as well as current solutions from GRACE Follow-On, suffer from temporal aliasing errors due to undersampling of the signal to be recovered (e.g., hydrology), which arise in terms of stripes caused by the north–south observation direction. In this paper, we investigate the potential of the proposed mass variation observing system by high–low inter-satellite links (MOBILE) mission. We quantify the impact of instrument errors of the main sensors (inter-satellite link and accelerometer) and high-frequency tidal and non-tidal gravity signals on achievable performance of the temporal gravity field retrieval. The multi-directional observation geometry of the MOBILE concept with a strong dominance of the radial component result in a close-to-isotropic error behavior, and the retrieved gravity field solutions show reduced temporal aliasing errors of at least 30% for non-tidal, as well as tidal, mass variation signals compared to a low–low satellite pair configuration. The quality of the MOBILE range observations enables the application of extended alternative processing methods leading to further reduction of temporal aliasing errors. The results demonstrate that such a mission can help to get an improved understanding of different components of the Earth system.
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Haworth, Thomas J., James Cadman, Farzana Meru, Cassandra Hall, Emma Albertini, Duncan Forgan, Ken Rice y James E. Owen. "Massive discs around low-mass stars". Monthly Notices of the Royal Astronomical Society 494, n.º 3 (7 de abril de 2020): 4130–48. http://dx.doi.org/10.1093/mnras/staa883.
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ABSTRACT We use a suite of smoothed particle hydrodynamic simulations to investigate the susceptibility of protoplanetary discs to the effects of self-gravity as a function of star–disc properties. We also include passive irradiation from the host star using different models for the stellar luminosities. The critical disc-to-star mass ratio for axisymmetry (for which we produce criteria) increases significantly for low-mass stars. This could have important consequences for increasing the potential mass reservoir in a proto Trappist-1 system, since even the efficient Ormel et al. formation model will be influenced by processes like external photoevaporation, which can rapidly and dramatically deplete the dust reservoir. The aforementioned scaling of the critical Md/M* for axisymmetry occurs in part because the Toomre Q parameter has a linear dependence on surface density (which promotes instability) and only an $M_*^{1/2}$ dependence on shear (which reduces instability), but also occurs because, for a given Md/M*, the thermal evolution depends on the host star mass. The early phase stellar irradiation of the disc (for which the luminosity is much higher than at the zero age main sequence, particularly at low stellar masses) can also play a key role in significantly reducing the role of self-gravity, meaning that even solar mass stars could support axisymmetric discs a factor two higher in mass than usually considered possible. We apply our criteria to the DSHARP discs with spirals, finding that self-gravity can explain the observed spirals so long as the discs are optically thick to the host star irradiation.
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Charbonnel, Corinne y Suzanne Talon. "Deep inside low-mass stars". Proceedings of the International Astronomical Union 4, S252 (abril de 2008): 163–74. http://dx.doi.org/10.1017/s1743921308022710.
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AbstractLow-mass stars exhibit, at all stages of their evolution, the signatures of complex physical processes that require challenging modeling beyond standard stellar theory. In this review, we recall the most striking observational evidences that probe the interaction and interdependence of various transport processes of chemicals and angular momentum in these objects. We then focus on the impact of atomic diffusion, large scale mixing due to rotation, and internal gravity waves on stellar properties on the main sequence and slightly beyond.
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Horst, L., P. V. F. Edelmann, R. Andrássy, F. K. Röpke, D. M. Bowman, C. Aerts y R. P. Ratnasingam. "Fully compressible simulations of waves and core convection in main-sequence stars". Astronomy & Astrophysics 641 (septiembre de 2020): A18. http://dx.doi.org/10.1051/0004-6361/202037531.
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Context. Recent, nonlinear simulations of wave generation and propagation in full-star models have been carried out in the anelastic approximation using spectral methods. Although it makes long time steps possible, this approach excludes the physics of sound waves completely and requires rather high artificial viscosity and thermal diffusivity for numerical stability. A direct comparison with observations is thus limited. Aims. We explore the capabilities of our compressible multidimensional Seven-League Hydro (SLH) code to simulate stellar oscillations. Methods. We compare some fundamental properties of internal gravity and pressure waves in 2D SLH simulations to linear wave theory using two test cases: (1) an interval gravity wave packet in the Boussinesq limit and (2) a realistic 3 M⊙ stellar model with a convective core and a radiative envelope. Oscillation properties of the stellar model are also discussed in the context of observations. Results. Our tests show that specialized low-Mach techniques are necessary when simulating oscillations in stellar interiors. Basic properties of internal gravity and pressure waves in our simulations are in good agreement with linear wave theory. As compared to anelastic simulations of the same stellar model, we can follow internal gravity waves of much lower frequencies. The temporal frequency spectra of velocity and temperature are flat and compatible with the observed spectra of massive stars. Conclusion. The low-Mach compressible approach to hydrodynamical simulations of stellar oscillations is promising. Our simulations are less dissipative and require less luminosity boosting than comparable spectral simulations. The fully-compressible approach allows for the coupling of gravity and pressure waves in the outer convective envelopes of evolved stars to be studied in the future.
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Zhang, Yan Yan y Cai Ying Chen. "Temperature Stress Analysis for Concrete Dam of Jiangya Hydropower Station". Applied Mechanics and Materials 556-562 (mayo de 2014): 683–86. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.683.
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Temperature is one of the main loads of concrete dam, adverse temperature load can lead to the dam body cracks, this paper study temperature load’s influence on concrete gravity dam. This paper use finite element method, it adopts finite element calculation software to establish concrete gravity dam’s finite element model of Jiangya hydropower station. Based on monitoring data of water temperature, air temperature, dam body temperature, foundation temperature about Jiangya hydropower station, calculates and analyzes temperature field of dam during operation period, researches stress variation law of dam under the influence of temperature field. The results showe that, temperature load has a great influence on the dam operation, but dam still meet code design requirements; when continuous high temperature during summer, dam should avoid operate under high water level; when continuous low temperature during winter, dam should avoid operate under low water level. Research results provide theoretical according for concrete gravity dam’s safe operation of Jiangya hydropower station.
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Bowman, D. M., C. Aerts, C. Johnston, M. G. Pedersen, T. M. Rogers, P. V. F. Edelmann, S. Simón-Díaz et al. "Photometric detection of internal gravity waves in upper main-sequence stars". Astronomy & Astrophysics 621 (enero de 2019): A135. http://dx.doi.org/10.1051/0004-6361/201833662.
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Context. Main sequence stars with a convective core are predicted to stochastically excite internal gravity waves (IGWs), which effectively transport angular momentum throughout the stellar interior and explain the observed near-uniform interior rotation rates of intermediate-mass stars. However, there are few detections of IGWs, and fewer still made using photometry, with more detections needed to constrain numerical simulations. Aims. We aim to formalise the detection and characterisation of IGWs in photometric observations of stars born with convective cores (M ≳ 1.5 M⊙) and parameterise the low-frequency power excess caused by IGWs. Methods. Using the most recent CoRoT light curves for a sample of O, B, A and F stars, we parameterised the morphology of the flux contribution of IGWs in Fourier space using an MCMC numerical scheme within a Bayesian framework. We compared this to predictions from IGW numerical simulations and investigated how the observed morphology changes as a function of stellar parameters. Results. We demonstrate that a common morphology for the low-frequency power excess is observed in early-type stars observed by CoRoT. Our study shows that a background frequency-dependent source of astrophysical signal is common, which we interpret as IGWs. We provide constraints on the amplitudes of IGWs and the shape of their detected frequency spectrum across a range of mass, which is the first ensemble study of stochastic variability in such a diverse sample of stars. Conclusions. The evidence of a low-frequency power excess across a wide mass range supports the interpretation of IGWs in photometry of O, B, A and F stars. We also discuss the prospects of observing hundreds of massive stars with the Transiting Exoplanet Survey Satellite (TESS) in the near future.
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Hillenbrand, Lynne A. "Age-related observations of low mass pre-main and young main sequence stars". Proceedings of the International Astronomical Union 4, S258 (octubre de 2008): 81–94. http://dx.doi.org/10.1017/s1743921309031731.
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AbstractThis overview summarizes the age dating methods available for young sub-solar mass stars. Pre-main sequence age diagnostics include the Hertzsprung-Russell (HR) diagram, spectroscopic surface gravity indicators, and lithium depletion; asteroseismology is also showing recent promise. Near and beyond the zero-age main sequence, rotation period or vsiniand activity (coronal and chromospheric) diagnostics along with lithium depletion serve as age proxies. Other authors in this volume present more detail in each of the aforementioned areas. Herein, I focus on pre-main sequence HR diagrams and address the questions: Do empirical young cluster isochrones match theoretical isochrones? Do isochrones predict stellar ages consistent with those derived via other independent techniques? Do the observed apparent luminosity spreads at constant effective temperature correspond to true age spreads? While definitive answers to these questions are not provided, some methods of progression are outlined.
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Borovin, Gennady Konstantinovich, Alexey Vasilyevich Grushevskii, Andrey Georgievich Tuchin y Denis Andreevich Tuchin. "Modern mission design with the high inclined orbit formation using gravity assists: main methods". Mathematica Montisnigri 49 (2020): 87–95. http://dx.doi.org/10.20948/mathmontis-2020-49-7.
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An effective space exploration is impossible without gravity assists (GA) using. Their application relaxes the constraints imposed on the space mission scenarios by the characteristic velocity budgets being realized at the current stage of development of space technology. A significant change in the inclinations of operational spacecraft (SC) orbits in flight aimed at studying the inner heliosphere from out-of ecliptic positions (the ESA “Solar Orbiter” mission, Russian “Interheliozond”) is needed to accomplish some prospective space missions. Low-cost tours for the high inclined orbit formation in the Solar system with use of gravity assists near its planets (Earth and Venus) with the full ephemeris using are considered. The limited dynamic possibilities of using gravity maneuvers require their repeated performance. Based on the formalization of the search for the GA- timetables with subsequent adaptive involvement of a large number of options, a high-precision algorithm for synthesizing chains of increasing gravity assists was built. Its use leads to a significant inclination change of the research SC's orbit without significant fuel consumption during a reasonable flight time.
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Yang, Hui, Yuanfei Jiang, Mengxiao Fu y Rui Wang. "Application of low temperature soaking liquid in combined freezing-based desalination processes in summer". Journal of Water Reuse and Desalination 11, n.º 3 (16 de junio de 2021): 425–38. http://dx.doi.org/10.2166/wrd.2021.122.
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Abstract In our previous study, it was noticed that the combined freezing, soaking and centrifugal desalination (FSCD) process is unsuitable to be applied in summer, because very little pure ice can be produced when the temperature of raw seawater used as soaking liquid reaches 27 °C. Therefore, two main efforts on the process optimization were made in this paper. One is that low-temperature seawater served as soaking liquid in all the experiments. In real industrial practice, the low-temperature soaking liquid can be obtained through melting pure ice products or recovering cold energy from cold concentrated brine. The effects of centrifugal parameters and soaking time on salt removal efficiency and ice yield rate were investigated. Second, the gravity-induced method was combined to form freezing, soaking, gravity-induced and centrifugal desalination (FSGCD) processes for further improvement of the salt removal efficiency. The influence of melting time of gravity-induced process was studied by keeping the samples ambient with an air temperature of 30 °C. Finally, the performance among different processes was compared. Results showed that the salt removal efficiency of the FSGCD process can reach up to 97.03%. The study is helpful to improve the process performance of soaking treatment in summer application.
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Lacour, S., R. Dembet, R. Abuter, P. Fédou, G. Perrin, É. Choquet, O. Pfuhl et al. "The GRAVITY fringe tracker". Astronomy & Astrophysics 624 (abril de 2019): A99. http://dx.doi.org/10.1051/0004-6361/201834981.
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Context. The GRAVITY instrument was commissioned on the VLTI in 2016 and is now available to the astronomical community. It is the first optical interferometer capable of observing sources as faint as magnitude 19 in K band. This is possible through the fringe tracker, which compensates the differential piston based on measurements of a brighter off-axis astronomical reference source. Aims. The goal of this paper is to describe the main developments made in the context of the GRAVITY fringe tracker. This could serve as basis for future fringe-tracking systems. Methods. The paper therefore covers all aspects of the fringe tracker, from hardware to control software and on-sky observations. Special emphasis is placed on the interaction between the group-delay controller and the phase-delay controller. The group-delay control loop is a simple but robust integrator. The phase-delay controller is a state-space control loop based on an auto-regressive representation of the atmospheric and vibrational perturbations. A Kalman filter provides the best possible determination of the state of the system. Results. The fringe tracker shows good tracking performance on sources with coherent K magnitudes of 11 on the Unit Telescopes (UTs) and 9.5 on the Auxiliary Telescopes (ATs). It can track fringes with a signal-to-noise ratio of 1.5 per detector integration time, limited by photon and background noises. During good seeing conditions, the optical path delay residuals on the ATs can be as low as 75 nm root mean square. The performance is limited to around 250 nm on the UTs because of structural vibrations.
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Żak, Bogdan y Stanisław Hożyń. "Low-Cost MEMS Accelerometers for Short Duration Micro ROV Distance Measurement". Solid State Phenomena 210 (octubre de 2013): 280–86. http://dx.doi.org/10.4028/www.scientific.net/ssp.210.280.
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In this paper the attempt to make an analysis of short duration Micro ROV distance measurement using low-cost MEMS accelerometers was presented. The main emphasis was placed on the gravity compensation and state estimation with Kalman filter method. The MEMS accelerometers error characteristics and the process model for measuring displacement of Micro ROV using accelerometers were presented. Finally, the examples of the verification results were performed.
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Lynch, S. V., E. L. Brodie y A. Matin. "Role and Regulation of σs in General Resistance Conferred by Low-Shear Simulated Microgravity in Escherichia coli". Journal of Bacteriology 186, n.º 24 (15 de diciembre de 2004): 8207–12. http://dx.doi.org/10.1128/jb.186.24.8207-8212.2004.
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ABSTRACT Life on Earth evolved in the presence of gravity, and thus it is of interest from the perspective of space exploration to determine if diminished gravity affects biological processes. Cultivation of Escherichia coli under low-shear simulated microgravity (SMG) conditions resulted in enhanced stress resistance in both exponential- and stationary-phase cells, making the latter superresistant. Given that microgravity of space and SMG also compromise human immune response, this phenomenon constitutes a potential threat to astronauts. As low-shear environments are encountered by pathogens on Earth as well, SMG-conferred resistance is also relevant to controlling infectious disease on this planet. The SMG effect resembles the general stress response on Earth, which makes bacteria resistant to multiple stresses; this response is σs dependent, irrespective of the growth phase. However, SMG-induced increased resistance was dependent on σs only in stationary phase, being independent of this sigma factor in exponential phase. σs concentration was some 30% lower in exponential-phase SMG cells than in normal gravity cells but was twofold higher in stationary-phase SMG cells. While SMG affected σs synthesis at all levels of control, the main reasons for the differential effect of this gravity condition on σs levels were that it rendered the sigma protein less stable in exponential phase and increased rpoS mRNA translational efficiency. Since σs regulatory processes are influenced by mRNA and protein-folding patterns, the data suggest that SMG may affect these configurations.
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Barrows, Larry y John D. Fett. "A high‐precision gravity survey in the Delaware Basin of southeastern New Mexico". GEOPHYSICS 50, n.º 5 (mayo de 1985): 825–33. http://dx.doi.org/10.1190/1.1441957.
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Since 1974, the Department of Energy has been studying bedded salt deposits in southeastern New Mexico as a possible location for disposing of defense‐generated transuranic and low‐level radioactive wastes. The program, known as the Waste Isolation Pilot Plant, includes intensive geologic characterization of about [Formula: see text] and construction of an underground test facility. The gravity survey reported here is part of the geologic site characterization. The gravity survey was conducted to delineate structural features near and at the proposed site. However, during the survey the gravity field was found to be dominated by effects of lateral density variations within relatively flat‐lying strata. Particularly distinctive is a pattern of elongate negative anomalies about one‐half mGal in amplitude. Boreholes in the anomalies encountered normal stratigraphy and no unusual geologic structures. However, borehole densilogs showed lower densities and uphole velocity surveys showed lower acoustic velocities than are measured outside of the anomalies. The low densities adequately account for the observed gravity anomalies. The regional stratigraphy contains water‐soluble minerals (halite, polyhalite, anhydrite‐gypsum, carbonates). Much of this material has dissolved and the region has been identified as a karstland. At the site, dissolution is slowly affecting the Rustler formation overlying the main salt‐bearing units. The low rock densities, associated with the negative gravity anomalies, are interpreted as due to alteration in the vicinity of solution conduits within the Rustler formation. This interpretation is supported by (1) partial coincidence between the negative gravity anomalies and closed topographic depressions (alluvial dolines); (2) greater anhydrite‐to‐gypsum conversion detected in boreholes within the anomalies; and (3) solution conduits encountered in one of the boreholes.
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Tian, F. Z., G. M. Xin, Q. Hai y L. Cheng. "An Investigation of Heat Transfer Characteristic of Cross Internal Helical Microfin Gravity Heat Pipe with Self-Rewetting Fluid". Advanced Materials Research 765-767 (septiembre de 2013): 189–92. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.189.
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Gravity heat pipe has been widely used in many heat transfer devices due to its high thermal conductivity, low cost and sample structure. In the paper, an experimental investigation of the gravity heat pipe with cross internal helical microfin gravity with two kind of working fluid (water and butyl alcohol solution with 5% mass fraction) was presented from horizontal and vertical position. The experimental results showed that in the horizontal position, self-rewetting fluid can significant increases the GHPCIHMs drying limit, decreases the thermal resistance and improves the heat transfer performance. In the vertical position, gravity effect play main functions on fluid return, self-rewetting has not been proved to have played a positive role on the heat transfer performance.
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Negulescu, Caterina, Kushan K. Wijesundara y Evelyne Foerster. "Seismic Damage Assessment of Regular Gravity Design Buildings". Key Engineering Materials 569-570 (julio de 2013): 294–301. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.294.
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During the past earthquakes, different low ductile failure modes are observed in the gravity design structures and thus, the most of existing damage indices may fail to assess the damage of gravity design structures accurately in referring to the two main performance levels: immediate occupancy and ultimate limit state. Therefore, this study investigates the possible damage indices for the damage assessment of gravity design frames. For this purpose, among the existing damage indices in the literature, this study considers the inter-story drift and the natural period based damage indices. In addition, two new damage indices based on the wavelet based energy and the dominant inelastic period of a building are also considered in this study. Furthermore, the damage assessment results from the four damage indices for three gravity design buildings are compared and discussed. From the comparison, linear correlations between the inter-storey drift based damage index and the wavelet energy based index, and dominant inelastic period based damage index are observed. Finally, this study concludes based on the observations that no significant effects of number of inelastic cycles to the damage assessment results for low ductile structures. However, this study also highlights the effects of number of inelastic cycles to the damage for medium and high ductile structures.
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Bailey, Brad T., Peter J. Morgan y Mark A. Lackie. "An assessment of the gravity signature of the Windmill Islands, East Antarctica". Antarctic Science 28, n.º 2 (6 de enero de 2016): 115–26. http://dx.doi.org/10.1017/s0954102015000565.
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AbstractA gravity survey was conducted on the Windmill Islands, East Antarctica, during the 2004–05 summer season. The aim of the study was to investigate the subsurface geology of the Windmill Islands area. Ninety-seven gravity stations were established. Additionally, 49 observations from a survey in 1993–94 were re-reduced and merged with the 2004–05 data. A three-dimensional subsurface model was constructed from the merged gravity dataset to determine the subsurface geology of the Windmill Islands. The main country rock in the Windmill Islands is a Garnet-bearing Granite Gneiss. A relatively dense intrusive charnockite unit, the Ardery Charnockite, generates the dominant gravity high of the study area and has been modelled to extend to depths of 7–13 km. It has moderate to steep contacts against the surrounding Garnet-bearing Granite Gneiss. The Ardery Charnockite surrounds a less dense granite pluton, the Ford Granite, which is modelled to a depth of 6–12 km and creates a localized gravity low. This granitic pluton extends at depth towards the east. The modelling process has also shown that Mitchell Peninsula is linked to the adjacent Law Dome ice cap by an ‘ice ramp’ of approximately 100 m thickness.
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Calil, Ana Maria y Cibele Andrucioli de Mattos Pimenta. "Gravity of injury and analgesia in patients who suffered traffic accidents". Acta Paulista de Enfermagem 21, n.º 3 (2008): 398–403. http://dx.doi.org/10.1590/s0103-21002008000300003.
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OBJECTIVE: Identifying the frequency and gravity of injuries in patients who suffered accidents in traffic and the analgesic drugs utilized. METHODS: Retrospective study, with a sample of 200 medical records of patients admitted to the emergency services of a reference hospital for trauma care. The gravity of the injuries was characterized by anatomic gravity rates and the analgesic therapy was based on the World Health Organization's Analgesic Ladder. RESULTS: The main findings pointed to injuries in limbs, head, face and outer surface as the most frequent, and, in 85% of the cases, gravity was equal or lower than 3; As for analgesia, it was verified that 46;6% of the patients received dipyrone and paracetamol. Among the opioids, meperidine was used in 10.4% of the cases. CONCLUSION: The gravity of most injuries was equal or lower to 3, indicating injuries of light, moderate and serious gravity, located especially in four body regions; regarding analgesia, dipyrone was shown to be the most commonly-used drug and a low use of opioids was verified.
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Charbonnel, C., T. Decressin, L. Amard, A. Palacios y S. Talon. "Impact of internal gravity waves on the rotation profile inside pre-main sequence low-mass stars". Astronomy & Astrophysics 554 (junio de 2013): A40. http://dx.doi.org/10.1051/0004-6361/201321277.
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Aditama, Maulana Rizki, Huzaely Latief Sunan, FX Anjar Tri Laksono, Gumilar Ramadhan, Sachrul Iswahyudi y Fadlin. "Integrated Subsurface Analysis of Thickness and Density for Liquefaction Hazard: Case Study of South Cilacap Region, Indonesia." Journal of Geoscience, Engineering, Environment, and Technology 6, n.º 1 (29 de marzo de 2021): 58–66. http://dx.doi.org/10.25299/jgeet.2021.6.1.5892.
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The thickness of the liquefable layer can be the factor inducing liquefaction hazard, apart from seismicity. Several studies have been conducted to predict the possibility of the liquefable layer based on the filed sampling. However, a detailed investigation of the subsurface interpretation has not been defined, in particular the thickness estimation of the liquefable layer. This study is carried out in south Cilacap area where potential liquefaction is exists due to the earthquake history data and near surface condition. The aim of this study is to investigate the physical properties and thickness distribution using GGMplus gravity data and resistivity data. This research is conducted by spectrum analysis of gravity model and 2D resistivity model . This study’s main results is by performing the residual gravity anomaly with the associated SRTM/DEM data to define the subsurface physical distribution and structural orientation of the area. Residual gravity anomaly is also separated through the low pass filter in order to have robust interpretation. The residual anomaly indicates that the area has identical structural pattern with geological and SRTM map. The results show a pattern of high gravity index in the northeast area of the study having range of 70 – 115 MGal gravity index, associated with the volcanic breccia, and a low gravity profile with less than 65 in the southwest, associated with the alluvial and water table dominated distribution. The thickness of Alluvial is determined by resistivity model with H1 at a range of 3 meters and H2 at a range of 4 m. This research is included in the potential liquefaction category with the potential for a large earthquake.
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Silvotti, R., M. Uzundag, A. S. Baran, R. H. Østensen, J. H. Telting, U. Heber, M. D. Reed y M. Vŭcković. "High-degree gravity modes in the single sdB star HD 4539". Monthly Notices of the Royal Astronomical Society 489, n.º 4 (12 de agosto de 2019): 4791–801. http://dx.doi.org/10.1093/mnras/stz2244.
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ABSTRACT HD 4539 (alias PG 0044 + 097 or EPIC 220641886) is a bright (V = 10.2) long-period V1093 Her-type subdwarf B (sdB) pulsating star that was observed by the Kepler spacecraft in its secondary (K2) mission. We use the K2 light curve (78.7 d) to extract 169 pulsation frequencies, 124 with a robust detection. Most of these frequencies are found in the low-frequency region typical of gravity (g-)modes, but some higher frequencies corresponding to pressure (p-)modes are also detected. Therefore HD 4539 is a hybrid pulsator and both the deep and surface layers of the star can potentially be probed through asteroseismology. The lack of any frequency splitting in its amplitude spectrum suggests that HD 4539 has a rotation period longer than the K2 run and/or that it is seen pole-on. From asymptotic period spacing we see many high-degree modes, up to l = 12, in the spectrum of HD 4539, with amplitudes as low as a few ppm. A large fraction of these modes can be identified and for ∼29 per cent of them we obtain a unique and robust identification corresponding to l ≤ 8. Our study includes also a new determination of the atmospheric parameters of the star. From low-resolution spectroscopy we obtain Teff = 22 800 ± 160 K, log g = 5.20 ± 0.02, and log(N(He)/N(H)) = −2.34 ± 0.05. By fitting the SED we obtain Teff = 23 470$^{+650}_{-210}$ K, R⋆ = 0.26 ± 0.01 R⊙, and M⋆ = 0.40 ± 0.08 M⊙. Moreover, from 11 high-resolution spectra we see the radial velocity variations caused by the stellar pulsations, with amplitudes of ≈150 m s−1 for the main modes, and we can exclude the presence of a companion with a minimum mass higher than a few Jupiter masses for orbital periods below ∼300 d.
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Chen, Yanguang, Yajing Li, Shuo Feng, Xiaoming Man y Yuqing Long. "Gravitational scaling analysis on spatial diffusion of COVID-19 in Hubei Province, China". PLOS ONE 16, n.º 6 (11 de junio de 2021): e0252889. http://dx.doi.org/10.1371/journal.pone.0252889.
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The spatial diffusion of epidemic disease follows distance decay law in geography and social physics, but the mathematical models of distance decay depend on concrete spatio-temporal conditions. This paper is devoted to modeling spatial diffusion patterns of COVID-19 stemming from Wuhan city to Hubei province, China. The modeling approach is to integrate analytical method and experimental method. The local gravity model is derived from allometric scaling and global gravity model, and then the parameters of the local gravity model are estimated by observational data and least squares calculation. The main results are as below. The local gravity model based on power law decay can effectively describe the diffusion patterns and process of COVID-19 in Hubei Province, and the goodness of fit of the gravity model based on negative exponential decay to the observational data is not satisfactory. Further, the goodness of fit of the model to data entirely became better and better over time, the size elasticity coefficient increases first and then decreases, and the distance attenuation exponent decreases first and then increases. Moreover, the significance of spatial autoregressive coefficient in the model is low, and the confidence level is less than 80%. The conclusions can be reached as follows. (1) The spatial diffusion of COVID-19 of Hubei bears long range effect, and the size of a city and the distance of the city to Wuhan affect the total number of confirmed cases. (2) Wuhan direct transmission is the main process in the spatial diffusion of COVID-19 in Hubei at the early stage, and the horizontal transmission between regions is not significant. (3) The effect of spatial lockdown and isolation measures taken by Chinese government against the transmission of COVID-19 is obvious. This study suggests that the role of urban gravity (size and distance) should be taken into account to prevent and control epidemic disease.
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Pail, R., J. Bamber, R. Biancale, R. Bingham, C. Braitenberg, A. Eicker, F. Flechtner et al. "Mass variation observing system by high low inter-satellite links (MOBILE) – a new concept for sustained observation of mass transport from space". Journal of Geodetic Science 9, n.º 1 (1 de enero de 2019): 48–58. http://dx.doi.org/10.1515/jogs-2019-0006.
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Abstract As changes in gravity are directly related to mass variability, satellite missions observing the Earth’s time varying gravity field are a unique tool for observing mass transport processes in the Earth system, such as the water cycle, rapid changes in the cryosphere, oceans, and solid Earth processes, on a global scale. The observation of Earth’s gravity field was successfully performed by the GRACE and GOCE satellite missions, and will be continued by the GRACE Follow-On mission. A comprehensive team of European scientists proposed the next-generation gravity field mission MOBILE in response to the European Space Agency (ESA) call for a Core Mission in the frame of Earth Explorer 10 (EE10). MOBILE is based on the innovative observational concept of a high-low tracking formation with micrometer ranging accuracy, complemented by new instrument concepts. Since a high-low tracking mission primarily observes the radial component of gravity-induced orbit perturbations, the error structure is close to isotropic. This geometry significantly reduces artefacts of previous along-track ranging low-low formations (GRACE, GRACE-Follow-On) such as the typical striping patterns. The minimum configuration consists of at least two medium-Earth orbiters (MEOs) at 10000 km altitude or higher, and one low-Earth orbiter (LEO) at 350-400 km. The main instrument is a laser-based distance or distance change measurement system, which is placed at the LEO. The MEOs are equipped either with passive reflectors or transponders. In a numerical closed-loop simulation, it was demonstrated that this minimum configuration is in agreement with the threshold science requirements of 5 mm equivalent water height (EWH) accuracy at 400 km wavelength, and 10 cm EWH at 200 km. MOBILE provides promising potential future perspectives by linking the concept to existing space infrastructure such as Galileo next-generation, as future element of the Copernicus/Sentinel programme, and holds the potential of miniaturization even up to swarm configurations. As such MOBILE can be considered as a precursor and role model for a sustained mass transport observing system from space.
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Zhu, Xiaojing, Ruizeng Zhang, Xiao Yu, Maoguo Cao y Yongxiang Ren. "Numerical Study on the Gravity Effect on Heat Transfer of Supercritical CO2 in a Vertical Tube". Energies 13, n.º 13 (7 de julio de 2020): 3502. http://dx.doi.org/10.3390/en13133502.
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The effects of gravity on the heat transfer performance of supercritical CO2 flowing within a vertical tube with a diameter of 4.75 mm are numerically studied in this paper. The main objectives are to comprehensively investigate the action of gravity and buoyancy on the supercritical heat transfer. An effective numerical method, which employs a modified Shear Stress Transfer k-ω model (SST k-ω), is applied at various gravity conditions. It is found that, for both upward and downward flows, the heat transfer of supercritical CO2 is improved with increased gravity magnitude. The effect of gravity on heat transfer are more pronounced under a low mass flux condition than that under a high mass flux condition and it is closely related to the variations of thermal properties. For the upward flow, the increased gravity magnitude accelerates the near wall fluid and creates a classic “M-shaped” radial velocity distribution. For the downward flow, the increased gravity magnitude decelerates the near wall fluid and creates a parabola-like radial velocity distribution. On one hand, the turbulent kinetic energies of both the upward and downward flows are enhanced as the gravity magnitude increases, which benefits heat transfer dominated by turbulent eddy diffusion. On the other hand, high-density fluid with high thermal conductivity occupies the near wall region as the gravity magnitude increases, which benefits heat transfer dominated by molecular diffusion. The results might provide some instructive advice to improve the design and operation safety of heat exchanger at various gravity conditions.
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Liu, Si Qing, Min Zhang, Wan Ping Wang y Bao Xu Song. "A Review on Reagents and Processes of Fine-Grained Cassiterite Flotation in Mining Engineering". Advanced Materials Research 577 (octubre de 2012): 151–54. http://dx.doi.org/10.4028/www.scientific.net/amr.577.151.
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Tin resources are abundant and complicated in China. Most of tin resources come from cassiterite. Normally the main beneficiation method of coarse cassiterite ore is gravity separation. However, as for the fine-grained cassiterite, flotation and joint processing techniques are generally selected to improve the low recovery from gravity separation. This paper outlines different kinds of cassiterite, collectors and depressants for cassiterite flotation and their using conditions and some reinforced methods in beneficiation of the fine-grained cassiterite for reference in mining industry.
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Batbaatar, Erdene, Munkhjargal Todbileg, Otgonbayar Sansar y Baatar Bataa. "The geophysical signature of Oyut deposits, Oyu Tolgoi, Mongolia". Mongolian Geoscientist 26, n.º 52 (23 de junio de 2021): 80–96. http://dx.doi.org/10.5564/mgs.v26i52.1323.
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The well-known Oyu Tolgoi Cu-Au group deposits can be divided into three main deposits: Hugo Dummett deposit (Hugo North and Hugo South), Oyut deposits (South Oyu, Southwest Oyu and Central Oyu), and Heruga deposit in the south. These deposits sit along 26 km long, north-northeast trending belt termed as the Oyu Tolgoi trend. This paper reviews investigations on geophysical signatures of the South Oyu, Southwest Oyu and Central Oyu deposits and compares geophysical models of the mineral deposits with their lithology, alteration, mineralization, and structures. A variety of datasets including induced polarization, ground magnetic, gravity survey are used in the study and generated inversion products of ground magnetic and gravity data with integrated interpretation. Typical responses from the Oyut deposits are: up to 0.1 mGal positive gravity anomaly above background, 100–200 nT low or high magnetic anomaly compared to background depending on the geological situations, and from 12 mV/V to 30 mV/V chargeability anomalies and low resistivity signatures from 100 ohm.m to 400 ohm.m. The interpreted geological-geophysical models of porphyry Cu-Au deposits presents in this study have emphasis on integrated interpretation of geophysical techniques, and inversions of gravity and magnetic data in gold rich porphyry copper system.
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Salimi, Hamidreza y Johannes Bruining. "The Influence of Heterogeneity, Wetting, and Viscosity Ratio on Oil Recovery From Vertically Fractured Reservoirs". SPE Journal 16, n.º 02 (23 de diciembre de 2010): 411–28. http://dx.doi.org/10.2118/140152-pa.
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Summary We use upscaling through homogenization to predict oil recovery from fractured reservoirs consisting of matrix columns, also called vertically fractured reservoirs (VFRs), for a variety of conditions. The upscaled VFR model overcomes limitations of the dual-porosity model, including the use of a shape factor. The purpose of this paper is to investigate three main physical aspects of multiphase flow in fractured reservoirs: reservoir wettability, viscosity ratio, and heterogeneity in rock/fluid properties. The main characteristic that determines reservoir behavior is the Péclet number that expresses the ratio of the average imbibition time divided by the residence time of the fluids in the fractures. The second characteristic dimensionless number is the gravity number. Upscaled VFR simulations, aimed at studying the mentioned features, add new insights. First, we discuss the results at low Péclet numbers. For only small gravity numbers, the effect of contact angle, delay time for the nonequilibrium capillary effect, the heterogeneity of the matrix-column size, and the matrix permeability can be ignored without appreciable loss of accuracy. The ultimate oil recovery for mixed-wet VFRs is approximately equal to the Amott index, and the oil production does not depend on the absolute value of the phase viscosity but on viscosity ratio. However, large gravity numbers enhance underriding, aggravated by large contact angles, longer delay times, and higher viscosity ratios. Layering can lead to an improvement or deterioration, depending on the fracture aperture and permeability distribution. At low Péclet numbers, the fractured reservoir behaves very similarly to a conventional reservoir and depends largely on the viscosity ratio and the gravity number. At high Péclet numbers, after water breakthrough, the oil recovery appears to be proportional to the cosine of the contact angle and inversely proportional to the sum of the oil and water viscosity. In addition, the mixed-wetting effect is more pronounced; there are significant influences of delay time (nonequilibrium effects), matrix permeability, matrix-column size, and the column-size distribution on oil recovery. At low gravity numbers and an effective length/thickness ratio larger than 10, the oil recovery is independent of the vertical-fracture-aperture distribution. For the same amount of injected water, the recovery at low Péclet numbers is larger than the recovery at high Péclet numbers.
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Calcaferro, Leila M., Leandro G. Althaus y Alejandro H. Córsico. "The coolest extremely low-mass white dwarfs". Astronomy & Astrophysics 614 (junio de 2018): A49. http://dx.doi.org/10.1051/0004-6361/201732551.
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Context. Extremely low-mass white dwarf (ELM WD; M⋆ ≲ 0.18–0.20 M⊙) stars are thought to be formed in binary systems via stable or unstable mass transfer. Although stable mass transfer predicts the formation of ELM WDs with thick hydrogen (H) envelopes that are characterized by dominant residual nuclear burning along the cooling branch, the formation of ELM WDs with thinner H envelopes from unstable mass loss cannot be discarded. Aims. We compute new evolutionary sequences for helium (He) core WD stars with thin H envelopes with the main aim of assessing the lowest Teff that could be reached by this type of stars. Methods. We generate a new grid of evolutionary sequences of He-core WD stars with thin H envelopes in the mass range from 0.1554 to 0.2025 M⊙, and assess the changes in both the cooling times and surface gravity induced by a reduction of the H envelope. We also determine, taking into account the predictions of progenitor evolution, the lowest Teff reached by the resulting ELM WDs. Results. We find that a slight reduction in the H envelope yields a significant increase in the cooling rate of ELM WDs. Because of this, ELM WDs with thin H envelopes could cool down to ~2500 K, in contrast to their canonical counterparts that cool down to ~7000 K. In addition, we find that a reduction of the thickness of the H envelope markedly increases the surface gravity (g) of these stars. Conclusions. If ELM WDs are formed with thin H envelopes, they could be detected at very low Teff. The detection of such cool ELM WDs would be indicative that they were formed with thin H envelopes, thus opening the possibility of placing constraints on the possible mechanisms of formation of this type of star. Last but not least, the increase in g due to the reduction of the H envelope leads to consequences in the spectroscopic determinations of these stars.
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Devi, N. Chandrachani, Aldo Rodríguez-Puebla, O. Valenzuela, Vladimir Avila-Reese, César Hernández-Aguayo y Baojiu Li. "The galaxy–halo connection in modified gravity cosmologies: environment dependence of galaxy luminosity function". Monthly Notices of the Royal Astronomical Society 488, n.º 1 (16 de junio de 2019): 782–802. http://dx.doi.org/10.1093/mnras/stz1664.
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Abstract We investigate the dependence of the galaxy–halo connection and galaxy density field in modified gravity models using the N-body simulations for f(R) and nDGP models at z = 0. Because of the screening mechanisms employed by these models, chameleon and Vainshtein, haloes are clustered differently in the non-linear regime of structure formation. We quantify their deviations in the galaxy density field from the standard Λ cold dark matter (ΛCDM) model under different environments. We populate galaxies in haloes via the (sub)halo abundance matching. Our main results are as follows: (1) The galaxy–halo connection strongly depends on the gravity model; a maximum variation of ${\sim }40{{\ \rm per\ cent}}$ is observed between halo occupational distribution (HOD) parameters; (2) f(R) gravity models predict an excess of galaxies in low-density environments of ${\sim }10{{\ \rm per\ cent}}$ but predict a deficit of ${\sim }10{{\ \rm per\ cent}}$ at high-density environments for |fR0| = 10−4 and 10−6 while |fR0| = 10−5 predicts more high-density structures; nDGP models are consistent with ΛCDM; (3) different gravity models predict different dependences of the galaxy luminosity function (GLF) with the environment, especially in void-like regions we find differences around ${\sim }10{{\ \rm per\ cent}}$ for the f(R) models while nDPG models remain closer to ΛCDM for low-luminosity galaxies but there is a deficit of ${\sim }11{{\ \rm per\ cent}}$ for high-luminosity galaxies in all environments. We conclude that the dependence of the GLF with environment might provide a test to distinguish between gravity models and their screening mechanisms from the ΛCDM. We provide HOD parameters for the gravity models analysed in this paper.
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MUÑOZ-MARTÍN, A., M. CATALÁN, J. MARTÍN-DÁVILA y A. CARBÓ. "Upper crustal structure of Deception Island area (Bransfield Strait, Antarctica) from gravity and magnetic modelling". Antarctic Science 17, n.º 2 (junio de 2005): 213–24. http://dx.doi.org/10.1017/s0954102005002622.
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Deception Island is a young, active volcano located in the south-western part of Bransfield Strait, between the Antarctic Peninsula and the South Shetland archipelago. New gravity and magnetic data, from a marine geophysical cruise (DECVOL-99), were analysed. Forty-eight survey lines were processed and mapped around Deception Island to obtain Bouguer and magnetic anomaly maps. These maps show well- defined groups of gravity and magnetic anomalies, as well as their gradients. To constrain the upper crustal structure, we have performed 2+1/2D forward modelling on three profiles perpendicular to the main anomalies of the area, and taking into account previously published seismic information. From the gravity and magnetic models, two types of crust were identified. These were interpreted as continental crust (located north of Deception Island) and more basic crust (south of Deception Island). The transition between these crustal types is evident in the Bouguer anomaly map as a high gradient area trending NE–SW. Both magnetic and gravity data show a wide minimum at the eastern part of Deception Island, which suggests a very low bulk susceptibility and low density intrusive body. With historical recorded eruptions and thermal and fumarolic fields, we interpret this anomaly as a partially melted intrusive body. Its top has been estimated to be at 1.7 km depth using Euler deconvolution techniques.
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Liu, Hao y Xiu Luan Li. "Research Status of Steam Assisted Gravity Drainage (SAGD) Technology". Advanced Materials Research 734-737 (agosto de 2013): 1246–52. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.1246.
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The exploitation of heavy oil and bitumen attracts more and more attention. Compared with normal light oil, heavy oil is of characteristics as high viscosity, low mobility and difficult for exploitation as a result of higher requirement of mining. The developing mechanism and process of SAGD is introduced in this paper. Some front technologies on the basis of SAGD are described about their application prospect as well. It is also summarized about SAGD development together with implementation in the field through detailed investigation of SAGD technology from home and abroad. Meanwhile, the main problems of SAGD facing to researchers are also summarized as well as the presentation of the corresponding improvement measures.
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Taguchi, Hiroyuki y Thet Mon Soe. "Myanmar’s Manufacturing Exports After the Lifting of Economic Sanctions". Foreign Trade Review 56, n.º 2 (23 de abril de 2021): 147–64. http://dx.doi.org/10.1177/0015732521995160.
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This article aims to evaluate Myanmar’s exports of manufacturing products by using a gravity trade model for emerging ASEAN economies. The main focus of this study is to assess whether Myanmar’s manufacturing exports have recovered in terms of the gravity trade standard of the other emerging ASEAN countries for the post-sanction period of 2013–2018. Unlike the previous studies, this article contributes to the literature by targeting the post-sanction period and by applying both in-sample and out-of-sample estimation methods to ensure the consistency and robustness of their results. The main findings from the gravity trade model estimation are summarised as follows: first, Myanmar’s manufacturing exports for the post-sanction period are still significantly below the level of the gravity trade standard. Second, the downward deviation from the standard could be explained by the two Myanmar-specific factors, that is, the low institutional quality and the Dutch Disease effect in Myanmar’s exports to Western countries, but not fully in those to Asian countries. The additional factor for the deviation against Asian countries might come from Myanmar’s sluggish participation in the international production networks. JEL Codes: F14, O53
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Bowman, D. M., S. Burssens, S. Simón-Díaz, P. V. F. Edelmann, T. M. Rogers, L. Horst, F. K. Röpke y C. Aerts. "Photometric detection of internal gravity waves in upper main-sequence stars". Astronomy & Astrophysics 640 (agosto de 2020): A36. http://dx.doi.org/10.1051/0004-6361/202038224.
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Context. Massive stars are predicted to excite internal gravity waves (IGWs) by turbulent core convection and from turbulent pressure fluctuations in their near-surface layers. These IGWs are extremely efficient at transporting angular momentum and chemical species within stellar interiors, but they remain largely unconstrained observationally. Aims. We aim to characterise the photometric detection of IGWs across a large number of O and early-B stars in the Hertzsprung–Russell diagram, and explain the ubiquitous detection of stochastic variability in the photospheres of massive stars. Methods. We combined high-precision time-series photometry from the NASA Transiting Exoplanet Survey Satellite with high-resolution ground-based spectroscopy of 70 stars with spectral types O and B to probe the relationship between the photometric signatures of IGWs and parameters such as spectroscopic mass, luminosity, and macroturbulence. Results. A relationship is found between the location of a star in the spectroscopic Hertzsprung–Russell diagram and the amplitudes and frequencies of stochastic photometric variability in the light curves of massive stars. Furthermore, the properties of the stochastic variability are statistically correlated with macroturbulent velocity broadening in the spectral lines of massive stars. Conclusions. The common ensemble morphology for the stochastic low-frequency variability detected in space photometry and its relationship to macroturbulence is strong evidence for IGWs in massive stars, since these types of waves are unique in providing the dominant tangential velocity field required to explain the observed spectroscopy.
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Guzik, Joyce A., T. H. Morgan, N. J. Nelson, C. Lovekin, K. Kosak, I. N. Kitiashvili, N. N. Mansour y A. Kosovichev. "2-D and 3-D models of convective turbulence and oscillations in intermediate-mass main-sequence stars". Proceedings of the International Astronomical Union 11, A29B (agosto de 2015): 540–43. http://dx.doi.org/10.1017/s1743921316006086.
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AbstractWe present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the Sun, using three separate approaches: 1) Using the 3-D planar StellarBox radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 2) Applying the spherical 3-D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone. Our goal is to determine whether core convection can excite low-frequency gravity modes, and thereby explain the presence of low frequencies for some hybrid γ Dor/δ Sct variables for which the envelope convection zone is too shallow for the convective blocking mechanism to drive gravity modes; 3) Applying the ROTORC 2-D stellar evolution and dynamics code to calculate evolution with a variety of initial rotation rates and extents of core convective overshooting. The nonradial adiabatic pulsation frequencies of these nonspherical models are calculated using the 2-D pulsation code NRO. We present new insights into pulsations of 1-2 M⊙ stars gained by multidimensional modeling.
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Fedorenko, A. K., A. V. Bespalova, O. K. Cheremnykh y E. I. Kryuchkov. "A dominant acoustic-gravity mode in the polar thermosphere". Annales Geophysicae 33, n.º 1 (27 de enero de 2015): 101–8. http://dx.doi.org/10.5194/angeo-33-101-2015.
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Abstract. The article presents a summary of the main findings of the systematic study of acoustic-gravity waves (AGWs) in the polar thermosphere. This study was based on the in situ measurements made by the Dynamics Explorer 2 (DE2) spacecraft late in its mission when it descended low enough (250–400 km). It was found out that AGWs in the polar thermosphere are observed within a narrow frequency band close to the Brunt–Väisälä frequency and with horizontal wavelengths about 500–600 km. The broadband spectrum of travelling ionospheric disturbance (TID) frequencies observed by radars is caused by the Doppler effect. The AGW amplitudes do not depend on the altitude, but grow almost linearly with the wind velocity. They propagate towards the wind.
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Koch, Igor, Mathias Duwe, Jakob Flury y Akbar Shabanloui. "Earth’s Time-Variable Gravity from GRACE Follow-On K-Band Range-Rates and Pseudo-Observed Orbits". Remote Sensing 13, n.º 9 (1 de mayo de 2021): 1766. http://dx.doi.org/10.3390/rs13091766.
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During its science phase from 2002–2017, the low-low satellite-to-satellite tracking mission Gravity Field Recovery And Climate Experiment (GRACE) provided an insight into Earth’s time-variable gravity (TVG). The unprecedented quality of gravity field solutions from GRACE sensor data improved the understanding of mass changes in Earth’s system considerably. Monthly gravity field solutions as the main products of the GRACE mission, published by several analysis centers (ACs) from Europe, USA and China, became indispensable products for quantifying terrestrial water storage, ice sheet mass balance and sea level change. The successor mission GRACE Follow-On (GRACE-FO) was launched in May 2018 and proceeds observing Earth’s TVG. The Institute of Geodesy (IfE) at Leibniz University Hannover (LUH) is one of the most recent ACs. The purpose of this article is to give a detailed insight into the gravity field recovery processing strategy applied at LUH; to compare the obtained gravity field results to the gravity field solutions of other established ACs; and to compare the GRACE-FO performance to that of the preceding GRACE mission in terms of post-fit residuals. We use the in-house-developed MATLAB-based GRACE-SIGMA software to compute unconstrained solutions based on the generalized orbit determination of 3 h arcs. K-band range-rates (KBRR) and kinematic orbits are used as (pseudo)-observations. A comparison of the obtained solutions to the results of the GRACE-FO Science Data System (SDS) and Combination Service for Time-variable Gravity Fields (COST-G) ACs, reveals a competitive quality of our solutions. While the spectral and spatial noise levels slightly differ, the signal content of the solutions is similar among all ACs. The carried out comparison of GRACE and GRACE-FO KBRR post-fit residuals highlights an improvement of the GRACE-FO K-band ranging system performance. The overall amplitude of GRACE-FO post-fit residuals is about three times smaller, compared to GRACE. GRACE-FO post-fit residuals show less systematics, compared to GRACE. Nevertheless, the power spectral density of GRACE-FO and GRACE post-fit residuals is dominated by similar spikes located at multiples of the orbital and daily frequencies. To our knowledge, the detailed origin of these spikes and their influence on the gravity field recovery quality were not addressed in any study so far and therefore deserve further attention in the future. Presented results are based on 29 monthly gravity field solutions from June 2018 until December 2020. The regularly updated LUH-GRACE-FO-2020 time series of monthly gravity field solutions can be found on the website of the International Centre for Global Earth Models (ICGEM) and in LUH’s research data repository. These operationally published products complement the time series of the already established ACs and allow for a continuous and independent assessment of mass changes in Earth’s system.
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Boland, A. V. y R. M. Ellis. "A geophysical model for the Kapuskasing uplift from seismic and gravity studies". Canadian Journal of Earth Sciences 28, n.º 3 (1 de marzo de 1991): 342–54. http://dx.doi.org/10.1139/e91-031.
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The Kapuskasing uplift is an oblique cross section of Archean crust exposed by a major thrusting event in Early Proterozoic times. Previous results from the traveltime and amplitude analysis of compressional-wave (P-wave) arrivals from a seismic-refraction experiment have been used to constrain the modelling of shear-wave (S-wave) arrivals and gravity anomalies along the seismic profiles. S-wave and P-wave velocity information have been combined to obtain the variations of Poisson's ratio within the crust. High and low Poisson's ratio values have been linked to the mafic and felsic content, respectively, of the Shield rocks. Density variations along the profiles, constrained by the P-wave velocity structures and the observed gravity anomalies, again have been linked to the lithological variations as observed in the exposed cross section. Geological models, constrained by the geophysical observations and the cross-sectional exposure, have been constructed for profiles across the northern and southern portions of the main uplift region. The results indicate an increase in pyroxene and garnetiferous gneisses with depth in the crust, as suggested by the high P-wave velocities (7.0–7.6 km/s), high densities (3050–3150 kg/m3, high Poisson's ratio values (0.26–0.28), and the petrological variations within the exposure. The presence of a low-velocity and low-density layer of tonalites under the surface greenstones has been established and can account for the low-velocity zones imaged along the Abitibi profile of this experiment and those imaged in other Shield refraction experiments.
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Parolin, Pia. "RADIAL GRADIENTS IN WOOD SPECIFIC GRAVITY IN TREES OF CENTRAL AMAZONIAN FLOODPLAINS". IAWA Journal 23, n.º 4 (2002): 449–57. http://dx.doi.org/10.1163/22941932-90000314.
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Increases in wood specific gravity (SG) with distance from pith are associated with the growth strategies of trees and their environments. In the present study, radial gradients in SG were analysed for 20 species from nutrient-rich whitewater floodplains (várzea), including seven pioneer species, and for 15 species from nutrient-poor blackwater floodplains (igapó) in Central Amazonia. Average SG increased from pith to bark by 12% in the species from igapó, compared to 16% in the nonpioneers and 35% in the pioneers from várzea. The increases lie in the range of tropical dry forests. SG variation follows the growth strategies of the trees. The main trend in nutrient-rich várzea is fast growth, with low SG wood initially and higher increases in SG. In nutrientpoor igapó, the tendency is relatively constant, slow growth and low SG changes throughout tree life.
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Cocciaro, Bruno, Sandro Faetti y Maurizio Nobili. "Capillarity effects on surface gravity waves in a cylindrical container: wetting boundary conditions". Journal of Fluid Mechanics 231 (octubre de 1991): 325–43. http://dx.doi.org/10.1017/s0022112091003415.
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Surface capillary–gravity waves are experimentally investigated in a cylindrical basin subjected to a horizontal oscillation by using a high-sensitivity optical method. We study the low-oscillation-amplitude regimes for a fluid which wets the vertical walls and we show that the presence of the capillary meniscus can effect greatly the main properties of the system. Both the free decay and the forced oscillations of surface oscillations are investigated. The amplitude, the phase and the damping of gravity waves are investigated in detail. The damping of the fundamental surface mode is found to exhibit nonlinear behaviour which is in qualitative agreement with the predictions of the Miles (1967) theory of capillary damping. The amplitude and the phase of gravity waves with respect to the oscillation of the container exhibit unusual behaviour which is strictly connected with the presence of the wetting boundary condition for the fluid at the vertical walls.
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Zhou, Hao, Zebing Zhou, Zhicai Luo, Kang Wang y Min Wei. "What can be expected from GNSS tracking of satellite constellations for temporal gravity field model determination?" Geophysical Journal International 222, n.º 1 (14 de abril de 2020): 661–77. http://dx.doi.org/10.1093/gji/ggaa177.
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SUMMARY The goal of this contribution is to investigate the expected improvement of temporal gravity field determination via a couple of high-low satellite-to-satellite tracking (HLSST) missions. The simulation system is firstly validated by determining monthly gravity field models within situ GRACE GPS tracking data. The general consistency between the retrieved solutions and those developed by other official agencies indicates the good performance of our software. A 5-yr full-scale simulation is then performed using the full error sources including all error components. Analysis of each error component indicates that orbit error is the main contributor to the overall HLSST-derived gravity field model error. The noise level of monthly solution is therefore expected to reduce 90 per cent in terms of RMSE over ocean when the orbit accuracy improves for a magnitude of one order. As for the current HLSST mission consisting of a current GNSS receiver and an accelerometer (10−10 and 10−9 m s–2 noise for sensitive and non-sensitive axes), it is expected to observe monthly (or weekly) gravity solution at the spatial resolution of about 1300 km (or 2000 km). As for satellite constellations, a significant improvement is expected by adding the second satellite with the inclination of 70° and the third satellite with the inclination of 50°. The noise reduction in terms of cumulative geoid height error is approximately 51 per cent (or 62 per cent) when the observations of two (or three) HLSST missions are used. Moreover, the accuracy of weekly solution is expected to improve 40–70 per cent (or 27–59 per cent) for three (or two) HLSST missions when compared to one HLSST mission. Due to the low financial costs, it is worthy to build a satellite constellation of HLSST missions to fill the possible gaps between the dedicated temporal gravity field detecting missions.
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Graña, Mariana y Alvaro Herráez. "The Swampland Conjectures: A Bridge from Quantum Gravity to Particle Physics". Universe 7, n.º 8 (28 de julio de 2021): 273. http://dx.doi.org/10.3390/universe7080273.
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The swampland is the set of seemingly consistent low-energy effective field theories that cannot be consistently coupled to quantum gravity. In this review we cover some of the conjectural properties that effective theories should possess in order not to fall in the swampland, and we give an overview of their main applications to particle physics. The latter include predictions on neutrino masses, bounds on the cosmological constant, the electroweak and QCD scales, the photon mass, the Higgs potential and some insights about supersymmetry.
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Zakariah, Muhammad Noor Amin, Norsyafina Roslan, Norasiah Sulaiman, Sean Cheong Heng Lee, Umar Hamzah, Khairul Arifin Mohd Noh y Wien Lestari. "Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia". Applied Sciences 11, n.º 14 (9 de julio de 2021): 6363. http://dx.doi.org/10.3390/app11146363.
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Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.
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Barker, A. J. "Tidal dissipation in evolving low-mass and solar-type stars with predictions for planetary orbital decay". Monthly Notices of the Royal Astronomical Society 498, n.º 2 (2 de septiembre de 2020): 2270–94. http://dx.doi.org/10.1093/mnras/staa2405.
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ABSTRACT We study tidal dissipation in stars with masses in the range 0.1–1.6 M⊙ throughout their evolution, including turbulent effective viscosity acting on equilibrium tides and inertial waves (IWs) in convection zones, and internal gravity waves in radiation zones. We consider a range of stellar evolutionary models and incorporate the frequency-dependent effective viscosity acting on equilibrium tides based on the latest simulations. We compare the tidal flow and dissipation obtained with the conventional equilibrium tide, which is strictly invalid in convection zones, finding that the latter typically overpredicts the dissipation by a factor of 2–3. Dissipation of IWs is computed using a frequency-averaged formalism accounting for realistic stellar structure for the first time, and is the dominant mechanism for binary circularization and synchronization on the main sequence. Dissipation of gravity waves in the radiation zone assumes these waves to be fully damped (e.g. by wave breaking), and is the dominant mechanism for planetary orbital decay. We calculate the critical planetary mass required for wave breaking as a function of stellar mass and age, and show that this mechanism predicts destruction of many hot Jupiters but probably not Earth-mass planets on the main sequence. We apply our results to compute tidal quality factors following stellar evolution, and tidal evolutionary time-scales, for the orbital decay of hot Jupiters, and the spin synchronization and circularization of binary stars. We also provide predictions for shifts in transit arrival times due to tidally driven orbital decay of hot Jupiters that may be detected with NGTS, TESS, or PLATO.
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Premji, Resmi, Nira Roopnarinesingh, Joshua Cohen y Sabyasachi Sen. "Cerebral Malaria: An Unusual Cause of Central Diabetes Insipidus". Case Reports in Endocrinology 2016 (2016): 1–4. http://dx.doi.org/10.1155/2016/2047410.
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Central diabetes insipidus is an uncommon feature of malaria. A previously healthy 72-year-old man presented with fever, rigors, and altered mental status after a recent trip to Liberia, a country known for endemic falciparum malaria. Investigations confirmed plasmodium falciparum parasitemia. Within one week after admission, the serum sodium rose to 166 mEq/L and the urine output increased to 7 liters/day. Other labs were notable for a high serum osmolality, low urine osmolality, and low urine specific gravity. The hypernatremia did not respond to hypotonic fluids. Diabetes insipidus was suspected and parenteral desmopressin was started with a prompt decrease in urinary output and improvement in mental status. Additional testing showed normal anterior pituitary hormones. The desmopressin was eventually tapered off with complete resolution of symptoms. Central diabetes insipidus occurred likely as a result of obstruction of the neurohypophyseal microvasculature. Other endocrinopathies that have been reported with malaria include hyponatremia, adrenal insufficiency, hypothyroidism, hypocalcemia, hypophosphatemia, hyper-, and hypoglycemia, but none manifested in our patient. Though diabetes insipidus is a rare complication of malaria, clinicians need to be aware of this manifestation, as failure to do so may lead to fatality particularly if the patient is dehydrated.
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Turck-Chieze, S., R. Bocchia, P. Boumier, M. Cantin, J. Charra, B. Cougrand, J. Cretolle et al. "The spatial Golf project". International Astronomical Union Colloquium 147 (1994): 532–36. http://dx.doi.org/10.1017/s0252921100026543.
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AbstractThis spatial experiment is under construction and has been defined as a 2 years mission on board SOHO, a satellite dedicated to the Sun which will be launched in mid 95. The main objectives are the detection of solar low degree acoustic modes and solar gravity modes for improving our knowledge of the solar nuclear region.
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Vølund, Per. "Concrete is the Future for Offshore Foundations". Wind Engineering 29, n.º 6 (diciembre de 2005): 531–63. http://dx.doi.org/10.1260/030952405776234571.
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This paper compares the costs of using concrete foundations against steel monopile foundations for offshore wind turbines, and argues that concrete foundations will be cheaper. Most offshore windfarms have steel monopile foundations, but in Denmark concrete gravity foundations have been used with success. Two projects have tendered for steel monopiles and for concrete foundations and have implemented the concrete foundations that proved cheaper. No project has tendered for both foundation concepts and chosen steel monopiles. Nysted Offshore Windfarm with concrete foundations has the cheapest foundations of any offshore windfarm so far. A conceptual foundation study carried out for the London Array West Offshore Windfarm indicates that the same method and very low-cost foundations as for Nysted can be used. Optimised design of light-weight concrete constructions is the key to low-cost installation. Cheap manufacture can be carried out near the site or at even lower cost in Eastern Europa from where it can be shipped at little extra cost. The main construction of steel monopile foundations will become twice as costly as of concrete gravity foundations, and though installation is more costly for the gravity foundations it seems most likely that tendering between steel monopile and concrete gravity for London Array West will prove concrete considerably cheaper. It is argued that these considerations are to a wide extent generally valid, and also for very large turbines in deeper water. Concrete foundations will in 2006 be installed at Lillegrunden Offshore Windfarm in Sweden, and at Belgian Thornton Bank in 2006–7. So indications are strong that concrete is the future for offshore foundations.
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Ern, M., P. Preusse, M. Krebsbach, M. G. Mlynczak y J. M. Russell. "Equatorial wave analysis from SABER and ECMWF temperatures". Atmospheric Chemistry and Physics 8, n.º 4 (21 de febrero de 2008): 845–69. http://dx.doi.org/10.5194/acp-8-845-2008.
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Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER satellite instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. For the examples of a QBO westerly phase (October–December 2004) and a QBO easterly phase (November/December 2005, period of the SCOUT-O3 tropical aircraft campaign in Darwin/Australia) in the lower stratosphere we find qualitatively good agreement between SABER and ECMWF in the longitude-time distribution of Kelvin, Rossby (n=1), and Rossby-gravity waves.