Large Gravity Research Articles

Geotechnical Forensic Investigations of a Gravity Dam: Addressing Seepage and Sliding Problems in the Basalt Foundations of Karjan Dam, Gujarat, India

Geotechnical forensic engineering plays a crucial role in identifying and mitigating potential issues in large gravity dams. The Karjan Dam in Gujarat, India, a 100-meter-high gravity dam built 38 years ago on Deccan basalt, encountered significant geotechnical challenges during construction due to early investigation oversights. These oversights failed to detect sub-horizontal weathered rock seams within the basalt during the pre-construction investigations, which could have posed significant seepage and sliding risks during the dam's operation. Subsequent detailed investigations during the construction phase revealed that these seams extended throughout the foundations of the dam blocks. In-situ shear tests were conducted to determine the shear parameters, namely cohesion (C) and the angle of internal friction (ϕ) of the seams. The test results indicated low shear strength parameters, necessitating a re-evaluation of the dam's safety. Stability analysis revealed that the spillway and certain non-overflow blocks were at risk of sliding and seepage after reservoir filling. To address these geotechnical challenges, a combination of treatments—including concrete shear keys, grouting, and design enhancements—was implemented to prevent sliding and control seepage. The timely forensic investigation and treatment during the construction stage ensured the dam's safety, which has operated without issues since 1986. This study underscores the critical importance of integrating engineering and geological assessments at various stages of dam construction. Re-evaluating and addressing evolving foundation conditions, particularly during construction, is essential for applying effective treatments to prevent dam failure during operation. The findings from this case study provide valuable geotechnical insights required for enhancing the safety and resilience of dam infrastructure globally.

Schwarzschild spacetime in fractal dimensions: Deflection of light, supermassive black holes and temperature effects

In this paper, we construct a Schwarzschild metric in the fractal dimension based on fractal calculus, and we study the deflection of light near the sun. It was observed that the new fractal spherically symmetric spacetime metric may describe supermassive black holes, which have been detected through various astronomical observations such as SDSS. We have discussed the deflection of light by the gravitational field of the sun. It was observed that the total deflection of light is affected by the fractal dimension. To estimate the numerical value of the fractal dimension, we have used the 2004[Formula: see text]analysis of almost 2 million VLBI observations of 541 radio sources made by 87 VLBI sites, which estimates the factor [Formula: see text] based on PNN formalism. It was observed that the fractal dimension is roughly less than unity. However, our analysis showed that large bending gravity gives fractal dimensions lower than unity to some extent. We also gave a naïve idea about the emission thermal Unruh process in fractal dimension. It was observed that both the temperature and the entropy of black holes are affected by the fractal dimension, and that for low numerical values, the entropy of the black hole is enhanced.

Extended uncertainty principle: A deeper insight into the Hubble tension?

The standard cosmological model, known as the ΛCDM model, has been successful in many respects, but it has some significant discrepancies, some of which have not been resolved yet. In measuring the Hubble-Lemaître parameter, there is an apparent discrepancy which is known as the Hubble tension, defined as differences in values of this parameter measured by the Type Ia Supernovae (SNeIa) data (a model-independent method) and by the Cosmic Microwave Background (CMB) radiation maps (a model-dependent method). Although many potential solutions have been proposed, the issue still remains unresolved. Recently, it was observed that the Hubble tension can be due to the concept of uncertainty in measuring cosmological parameters at large distance scales through applying the Heisenberg Uncertainty Principle (HUP) in cosmological setups. Extending this pioneering idea, in the present study we plan to incorporate the Extended Uncertainty Principle (EUP) containing a minimal fundamental measurable momentum (or equivalently, a maximal fundamental measurable length) as a candidate setup for describing large-scale effects of Quantum Gravity (QG) to address the Hubble tension and constrain the EUP length scale. In this regard, by finding a relevant formula for the effective photon rest mass in terms of the present-time value of the Hubble-Lemaître parameter, we see that discrepancies in the value of photon rest mass associated with the Hubble-Lemaître parameter values estimated from model-independent and model-dependent methods perhaps is the cause of Hubble tension. We show explicitly that the presence of a non-zero minimal uncertainty in momentum (or non-zero maximal uncertainty in position) measurements as a consequence of the large distance quantum gravity effect addresses the Hubble tension satisfactorily without having to invoke new physics. Moreover, we use the formula for the effective photon rest mass to find some relevant lower bounds on the EUP length scale.

Integration of Large Multielement Geochemical, Aeromagnetic, and Gravity Data to Geologically Map a Largely Covered Area: A Case Study from the Central African Copperbelt in Northern Zambia

Abstract This study provides a method to map lithology, stratigraphy, and structures in areas with limited outcrop using mineral exploration data from multielement soil geochemical surveys, airborne and ground geophysical surveys, and drill hole data sourced from multiple exploration companies and campaigns. The 45- by 50-km study area is located in the southern portion of the Congolese Copperbelt, where the regional geology, structure, and overall basin architecture were not well understood, partly due to thick saprolite cover. The results demonstrate that the integration of such data sets allows the creation of a geologically coherent map, which can then be used to investigate basin architecture and identify basin-forming structures.

Undertaking risk assessments for Hong Kong reservoirs

The 2013 RARS (risk assessments for reservoir safety management) guidance was developed for the Environment Agency to provide a robust three-tiered framework for the risk analysis, assessment and management of reservoirs in the United Kingdom. The methods presented can be used to assess a reservoir's risk in its entirety, either at a qualitative level (tier 1) or more in-depth quantitative levels (tiers 2 and 3). Binnies undertook RARS assessments of reservoirs for Hong Kong's Water Supply Department. This paper identifies the limitations and challenges encountered when applying the guidance in Hong Kong, beyond its original intended purpose. It outlines the adjustments made to assess the Hong Kong service reservoirs at tier 1, and large embankment and gravity dams at tier 2. Some of the differences include (i) how the nature of loading and external threats differs due to geographical and locational differences; (ii) how consequences of reservoir failure differ due to topology, population densities and cultural differences in the reservoirs’ uses and (iii) how the reservoirs are atypical from ‘Pennine’ type UK embankment dams, from which most UK empirical methods are derived.

DETERMINATION OF THE SIZE OF MEDIUM GRANULES IN FREE ABRASIVE PROCESSING TECHNOLOGY AND THE SIZE OF THE RESERVOIR OF A MACHINE FOR VIBRATION PROCESSING OF PARTS

It is noted that the process of vibration processing of parts is carried out by the relative movement and mutual pressure of granules of the medium and the parts being processed circulating in the oscillating reservoir. It is noted that the removal of defects from the surface of a part is carried out by the processes of microcutting and elastoplastic deformation. It is indicated that despite the effectiveness of vibration processing, its capabilities are limited to performing simple operations and have not been sufficiently studied. The effectiveness of vibration processing depends on a number of factors, among which the size of the medium granules and the size of the machine reservoir play a significant role. To determine these factors, the kinematics of the finishing and grinding process was considered, and the joint movement of the medium granule and the part was taken into account. The removal of microchips along the entire length of the machined surface during one period of oscillation of the machine reservoir and the damping properties of the material of the working medium used were also taken into account. It has been established that, depending on the shape of the part, its position and direction of movement in the reservoir, the angle of contact with the granules can vary from 0 to 90º. In this regard, cases of encounters between granules and parts are considered. It has been established that the unfavorable case of a meeting occurs at the right angle of their collision. It is concluded that the removal of microchips from the surface of parts is theoretically inversely proportional to the size of the medium granules. It has been determined that the increase in damping of the medium caused by a decrease in the size of the granules can be compensated by increasing the amplitude of the oscillations of the reservoir and the use of granules with a large specific gravity. The choice of granule size is also limited by the conditions of their access to the surfaces being treated, while the conditions for eliminating the possibility of granules jamming are met. It has been experimentally confirmed that the reservoir with a “U” – shaped cross-section turned out to be the best, due to the absence of stagnant zones in it. It has been established that as the cross-section of the reservoir increases, the productivity of the machine will decrease. Intensifying the process by increasing the amplitude is unacceptable, since this causes the appearance of deep defects on the treated surfaces. To increase processing efficiency, it is necessary to increase the volume of the reservoir by lengthening it, rather than increasing its cross-section.

DEVELOPMENT OF A GIS-BASED SYSTEM FOR IRRIGATION MANAGEMENT AND FLOW DISTRIBUTION

Abstract. The systematic management of irrigation operation of medium and large gravity irrigation systems (IS) significantly affects the delivery efficiency of irrigation from the source to the farm level. An interactive spatial database that integrates system data handling and irrigation distribution assessment functionality can be implemented, which has not yet been developed in existing NIS in the Philippines. This study proposes a framework model in developing a geographic information system (GIS) database for irrigation systems that integrates a GIS-based irrigation network distribution analysis model. The creation of a model framework for the development of a functional GIS-based database for IS management and flow distribution is comprised of five stages namely: (1) selection and determination of significant irrigation system data, (2) determination of required estimation parameters, (3) GIS development, (4) irrigation network distribution model development, and (5) selection of applicable water distribution assessment techniques. The GIS-based database and integrated model for irrigation provide essential data records of the irrigation system that could easily be viewed systematically and integrated into any GIS. In addition, data packages can easily be shared and run even on low-end computers. Features of the proposed irrigation model include flow volume simulation, time of delivery simulation, irrigation scheduling, remote sensing model integration for automated evapotranspiration computation, volumetric assessment, assessment of the timing of irrigation, and distribution optimization.

Tropical cyclone “Vayu” generated gravity waves (20–60 min) in the mesosphere and lower thermosphere over Kolhapur

Tropical cyclones are one of the potential sources of gravity waves, which can transport energy and momentum to higher heights through their vertical propagation and interaction with the background flow and thereby influence the dynamics of the upper atmosphere. High-resolution wind data acquired by the Medium Frequency (MF) radar at Kolhapur (16.69°N, 74.24°E) are utilized to study the high frequency gravity waves (20–60 min) associated with the tropical cyclone named “Vayu” formed in the Indian Arabian Sea in June 2019. An enhancement of the gravity wave (GW) activities in the meridional wind is observed during 13–15 June 2019. The source of the gravity wave is the tropical Vayu cyclone of category 2 storm. We employed the gravity wave variance data from NASA's Atmospheric Infrared Sounder (AIRS) satellite for our analysis over stratospheric heights. The enhancement of gravity wave variance in both the stratosphere mesosphere heights and the low values of OLR indicate the strong convection associated with cyclone, the source of observed gravity waves. In the present study we analyzed the horizontal propagation direction of the cyclone generated gravity waves using perturbation ellipse, it is found to be in the north–south plane. The temperature profiles obtained from the SABER instrument on board TIMED satellite indicate the presence of mesospheric inversion layer with an amplitude of nearly 40 K on the day of large gravity wave variance (June 13, 2019). These results indicate the cyclone can generate gravity waves which can propagate to higher heights and modify the MLT thermal structure, providing evidence for the vertical coupling between lower and upper atmosphere.

Perceived Obstacles in Land Use Change for Hybrid Sweetgum Plantations: Landowner Opinions from the South Central United States

Abstract Hybrid sweetgum (Liquidambar styraciflua × L. formosana) has received considerable attention as a potential feedstock for traditional and nontraditional forest-based enterprises due to its fast growth and large specific gravity. However, the perceptions of landowners are important to understand the degree of acceptance concerning land use change to consider this opportunity in the United States. We administered a survey instrument to three thousand landowners representing the states of Texas, Oklahoma, Louisiana, and Arkansas where hybrid sweetgum plantations would be feasible. A seemingly unrelated regression analysis was used to explore the attributes that may influence the environmental and economic obstacles in land use change for hybrid sweetgum plantations. Study results suggest that landowners who perceived higher importance of marketing aspects of hybrid sweetgum expressed greater economic concerns for land use change. In contrast, those having higher planted pine acres had higher environmental concerns about land use change. Female landowners were more concerned than their male counterparts. Landowners need access to accurate information from their trusted sources to make informed management decisions, especially when making decisions to adopt new opportunities such as hybrid sweetgum. Study Implications: Study results reveal the need for outreach to landowners in the south central United States, as many were not aware of fast-growing hardwood species such as hybrid sweetgum. Information on growth potential, economics, and management techniques can help facilitate the adoption of hybrid sweetgum. Field visits and peer-to-peer learning facilitated by early adopters can be effective strategies for outreach.

Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432

Context. Rocky planets form by the concentration of solid particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in the disk available in the solid phase at the time the planets were forming. Studying the dust before it gets incorporated in planets provides a valuable diagnostic for the material composition. Aims. We aim to constrain the structure and dust composition of the inner disk of the young Herbig Ae star HD 144432, using an extensive set of infrared interferometric data taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, and to fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem to assess the hidden diversity of minerals occurring in a planet-forming disk such as HD 144432. Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that the dark regions in the disk at ~0.9 au and at ~3 au are gaps opened by planets, we estimate the masses of the putative gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission (τ < 0.4) from the inner two disk zones (r < 4 au) at λ > 3 µm. Our silicate compositional fits confirm radial mineralogy gradients, as for the mass fraction of crystalline silicates we get around 61% in the innermost zone (r < 1.3 au), mostly from enstatite, while only ~20% in the outer two zones. To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-rich model provides a better fit to the spectral energy distribution. Our GGchem calculations also support an iron-rich and carbon-poor dust composition in the warm disk regions (r < 5 au, T > 300 K). Conclusions. We propose that in the warm inner regions (r < 5 au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the need for detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.

Corrosion Behavior of Al Alloy A6061 Jointed with High-Tensile Strength Steel By Friction Stir Welding in NaCl Solution

In recent years, weight reduction of automobile bodies has been effective in reducing carbon dioxide emissions. For this reason, the replacement of steel, which has a large specific gravity, with aluminum alloys and carbon fiber reinforced plastics is being promoted for the right materials in the right places. In this case, an appropriate dissimilar material joining method is needed in terms of ease of assembly, joining performance, and cost. Friction stir welding (FSW) has emerged as a promising joining method for a variety of engineering applications. FSW is a solid-phase joining technique that has been shown to have significant advantages over conventional welding in terms of the strength and quality of the joints produced. However, during joining of metallic materials by FSW, microstructural changes may occur that affect their corrosion degradation. In this study, the corrosion behavior of A6061 jointed with high-strength steel (SPCC980) by FSW in aqueous NaCl solution and the effect of Al alloy microstructural changes on it were investigated.In this study, FSW was performed on A6061 and SPCC980 steel plates, and galvanic corrosion behavior was investigated by immersion tests and surface observations, as well as electrochemical measurements of Al alloys. Immersion tests were performed in 1 M NaCl solution. Micro electrochemical polarization tests of A6061 were also performed to investigate the corrosion behavior.In the immersion test of the galvanic couple of A6061 and SPCC980 steel plates in NaCl solution, galvanic corrosion occurred with the Al alloy as the anode and the steel plate as the cathode, and hydrogen evolution was observed mainly from the BM site on A6061 in the initial stage of immersion. This is due to the hydrogen evolution reaction occurring inside the pitting corrosion of the A6061. The pits was formed near Fe-rich inclusions in the BM site. In the HAZ site, corrosion propagated from Fe-rich inclusions along grain boundaries, but no pitting corrosion was formed. In the NZ site, minor localized corrosion was developed. These results indicate that the susceptibility to localized corrosion and its morphology differ in each site on the A6061. The difference in localized corrosion susceptibility on the A6061 was considered to be caused by the difference in the distribution of Fe-rich inclusions. However, the fact that the size and number of Fe-rich inclusions in each site did not differ suggests that the difference in anodic dissolution activity near Fe-rich inclusions affects pitting corrosion susceptibility in each site. A6061 alloy is a precipitation-strengthened Al alloy reinforced by β'' phase, which is a metastable phase of Mg2Si, and dense precipitation of β'' phase was observed in the BM site. Therefore, the reason for the higher localized corrosion susceptibility of BM is related to the precipitation of the β'' phase.This paper is based on results obtained from a project, JPNP14014, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Experimental and Simulation Investigation on Ball-Sealer Transport and Diversion Performance Aided by Machine Learning Method

Summary Ball-sealer diversion has been proven to be an effective and economical way to increase fractures and fracturing volume in multistage hydraulic fracturing and matrix acidizing treatments. However, designing and implementing a successful ball-sealer diversion treatment is still challenging. Typically, operators rely on empirical data to determine diversion parameters and need an understanding of accurate ball transport and diversion behaviors. A model for optimizing operating parameters, including fluid and ball properties, and predicting the diversion performance of ball sealers before treatment is needed for designing the fracturing process. In this work, we systematically investigated ball-sealer diversion using experimental and numerical methods. The resolved model of computational fluid dynamics (CFD) and discrete element method (DEM) is first developed to simulate the transport of a large ball in a horizontal wellbore with side holes. The experimental results validated the numerical model. The effects of the ball position in the pipe, flow ratio of the hole to pipe, injection flow rate, and ball density on the diversion performance were studied under field parameters. The results show that the ball sealer easily misses the heel-side perforation due to the inertial effect and travels to the toe side due to the large inertia and turbulent flow. The ball position and flow rate ratio are crucial for the diversion performance. There is a threshold value of the ball position under the specific condition, and the ball successfully turns to the perforation only when the threshold distance is met. A ball sealer closer to the perforation will have a larger probability of blocking the hole than the ball at the other side of the wellbore. The larger the flow rate ratio, the more the drag force on the ball, and the ball can successfully divert to the perforation despite the ball being far from the hole. The injection flow rate and ball density negatively correlate with the diversion performance due to the large inertia and gravity. The best classification result with the F1 score of 87.0% in the prediction set was achieved using the random forest (RF) algorithm. It provides new insight into developing ball sealers and adjusting fracturing parameters based on machine learning (ML) methods.

Seismic Performance of Reinforced Concrete Buildings with Different Lateral Load

Shear wall, steel bracing and combined system are the most commonly used lateral-load resisting technique for high-rise buildings. Shear walls have very high in-plane strength and stiffness, which can be used simultaneously for resisting large horizontal and gravity loads. The aim of this study is to examine how well reinforced concrete buildings withstand seismic activity using various systems for resisting lateral loads. In this study, a reinforced concrete building with 12 floors (G+12) and 5 X 5 bays is selected, and various lateral load resisting frame systems are applied in different positions. These are shear wall, bracings, shear wall-bracings combinations (Combined) at five different locations/patterns i.e., at outer corners (Type- I), center of outer sides (Type- II), middle corners (Type- III), center of middle sides (Type- IV), and inner core and middle sides (Type- V) respectively. A total of sixteen models are created for this study, with one being a bare frame and the other fifteen consisting of three types of lateral load resisting systems arranged in five different configurations each. With the assistance of ETABS all models are analyzed by Equivalent Static Analysis and Response Spectrum Analysis. The performance of building is evaluated on the basis of following parameters- maximum storey displacement, maximum storey drift and storey shear. At last the results are compared for different models. Among the three systems, the shear wall system exhibits the least displacement and the highest stiffness. Response of combined system is better than that of bracing system. Overall, the Type II shear wall model is more earthquake-resistant and structurally efficient than the other fifteen models. Key Words: Equivalent Static Analysis, Response Spectrum Analysis, Maximum storey displacement, Maximum storey drift, Storey shear

Influence of Different European Code Provisions for Capacity Design on the Seismic Performance of Reinforced Concrete Frames

Performance-based seismic codes ensure proper inelastic behaviour of reinforced concrete frames through capacity design, among others. This strategy relies not only on avoiding brittle failures and providing ductility to plastic hinges but also in their distribution within the frame aimed at a greater number of storeys involved in the eventual collapse mechanism. Although codes are generally in agreement to some basic principles in order to ensure capacity design, they show some discrepancies regarding the specific strategies. In this paper, capacity design provisions proposed by some European current codes—Eurocode 8, Italian NTC, and Spanish NCSE-02—are compared, and their effectiveness is discussed. The alternative formulation proposed by Italian code for “strong column–weak beam” turns out to be not suitable under specific circumstances, such as with large gravity loads or significant cantilever deformation in lower storeys. Regarding the value of axial load in columns to be considered for the calculation of shear and moment capacities, provisions in the three codes could eventually cause unconservative design for perimeter columns. The Spanish whole set of provisions is proved to not be effective due to their different fundamentals—they are based on overstrength instead of capacity. For all the three cases, some alternative procedures are suggested in this work.

The Case for Future Gravity Science Investigations at Saturn with a Planetary Orbiter

The next phase in the robotic exploration of the Saturnian system will target unresolved questions about the gas giant’s atmosphere, interior, magnetosphere, and rings that were left open by investigations on board the Cassini mission. Among these, we find gravity science objectives, which relate mainly to explaining the origin of the large wind-induced gravity signal and reconciling existing incongruities regarding the internal density distribution. Here we attempt to identify which future observations may yield additional information about Saturn’s internal mechanisms. We report on the results of precise numerical simulations of a gravity science experiment carried out with a planetary orbiter in the 2040s and characterized by varying periapsis altitude over the 1 bar planetary surface. The goal is to identify achievable measurement requirements that can advance the current understanding of Saturn’s interior and atmospheric dynamics. We find that inclined, elliptical orbits with low-altitude closest approaches over the northern hemisphere can improve the present determination of the gravity field coefficients by up to 1 order of magnitude, provided that at least a dozen pericenters are devoted to gravity science. Furthermore, if future observations are combined with the available Cassini Grand Finale data in the southern hemisphere, a significant improvement in terms of maximum measurable gravity field degree is observed.

Study on safety assessment methods of gravity anchors based on a simplified mechanical model

Gravity anchor blocks are a common type of ground anchor used for suspension bridges, whose bearing depends on its large body and gravity. As there is no stratum requirement, the safety of the anchor block is important for bridge stability. This study summarizes all available estimation indexes, calculating methods, and evaluation criteria for gravity anchor block safety for the Ruili bank of the Banjin Dam grand suspension bridge. The anti-overturning, anti-sliding, base stress, and deformation safeties were comprehensively evaluated using methods including the suggested specification method (SM), simplified mechanical method (SMM), and finite element method (FEM), the results of which were compared and analyzed. The reasons for errors and improved formulas and working conditions were presented. The main conclusions were as follows. 1) The methods for calculating different evaluation indexes according to specifications lack consistency. Moreover, FEM requires that designers have good computer skills and has low feasibility in practice. 2) The SMM for gravity anchor block safety estimation as described in this study, whose indexes cover systematic and overall, the computational formula is simple and speedy, with relatively conservative results and good practicability. 3) SM, SMM, and FEM were all used for the safety estimation of gravity anchor blocks in Ruili bank. The anti-overturning and anti-sliding stability coefficients must all meet the specification requirements of 2.0. SM cannot be used to estimate the base tensile stress under limited conditions. SMM denoted tensile stress at 2.5 times the main cable design force, compared to 3.2 P for FEM. Deformation calculation methods are not given by SM, but can be suggested by SMM based on the elastic mechanics. The horizontal displacements under design load conditions were 122 mm (SMM), 108 mm (FEM), and 44 mm (composite foundation treated by root piles), with a safety standard of <80 mm. The vertical displacements were 338 mm (SMM), 110 mm (FEM), and 123 mm (composite foundation treated by root piles), with a safety standard of <160 mm. These findings proved the feasibility of SMM for the safety design of gravity anchor blocks in cases lacking regional experience.

Modeling and Optimization of a Large-Load Magnetic Levitation Gravity Compensator

This article presents the modeling and optimization design of a large load magnetic levitation gravity compensator. The proposed magnetic levitation gravity compensator comprises three layers of two-dimensional (2D) permanent magnet arrays. The middle mover layer can generate a large passive levitation force to compensate for the gravity of large loads in some magnetic levitation systems, such as the measurement framework in lithography machines or large space optical equipment to be tested on the ground. To accurately predict the passive levitation force, an improved magnetic charge model is proposed, in which the actual working points of each permanent magnet (PM) are considered. The accuracy of the improved model is verified via three-dimensional (3D) finite element simulation. Genetic algorithm (GA) is then adopted as the parameter optimization method to reduce the levitation force stiffness within the effective vertical displacement to the greatest extent possible. Compared with the levitation force performance without parameter optimization, the sensitivity of the levitation force with vertical displacement is significantly reduced. In addition, the mechanical structure is designed, and the mechanical strength is checked. Finally, a magnetic levitation gravity compensator prototype with a passive levitation force of 6200 N is manufactured and tested. The tested values of the levitation force match well with the analytical and simulation results. The tested levitation force stiffness within 4 mm is less than 50 N/mm and basically remains unchanged, which is a superior performance for magnetic levitation systems.

Unzipping supercontinent Pangea: Geologic, potential field data, and buried structures, and a case for sequential Atlantic opening

Amalgamation of Pangea culminated with zippered N-to-S closing of the Theic ocean during the Alleghanian orogeny. Transpressional-rotational collision produced widespread dextral faulting throughout the eastern Appalachian hinterland, and thrust faulting in the western hinterland and foreland. The partially buried southern Appalachian Eastern Piedmont fault system is a product of late Paleozoic transpressional dextral faulting. Eastern Piedmont fault system faults are cut by two 200–190 Ma Central Atlantic Magmatic Province (CAMP) diabase dike sets (∼NW and NS), which postdate initial rifting, producing the Late Triassic-Early Jurassic basins. Sinistral reactivation of suitably oriented Paleozoic faults (e.g., Towaliga) that offset Jurassic dikes implies faulting is coeval with CAMP dike emplacement, or occurred very soon after 200–190 Ma dike emplacement. A large NE-striking sinistral fault (Estill fault) offsets magnetic and gravity highs in the Brunswick (Charleston) terrane in South Carolina and Georgia. This fault is at least 185 km long, with ca. 75–80 km maximum of sinistral separation. The Estill fault geometry agrees with the stress field associated with Central Atlantic Magmatic Province dike emplacement. We conclude that movement along the Estill and other sinistral faults represents Early Jurassic displacement that is well documented in eastern North America prior to Atlantic opening. The early Mesozoic post-failed rifting (basin formation) preceded dike emplacement and pre-spreading sinistral faulting. We recognize four stages in the Late Triassic–Jurassic tectonics and kinematics of eastern North America based on field, crosscutting relationships, and available geophysical data: (1) initial W-to-E failed transtensional rifting with formation of the S-to-N-younging Triassic-Jurassic basins; (2) CAMP diabase dikes intruded 200–190 Ma; (3) sinistral movement of large blocks of crust in the North Atlantic region including southeastern North America; and (4) spreading and opening of the Atlantic Ocean 195–170 Ma. These stages mark the reversal of Alleghanian rotational dextral transpressional (zippered) collision forming Pangea supercontinent and ‘unzipping’ the supercontinent prior to Atlantic opening.

The Effect of Currents on Large Surface Gravity Waves Under Cyclonic Conditions in the South/Southeastern Brazil

AbstractAlthough ocean surface currents are not accounted for in most wave modeling studies, recent works have demonstrated that ocean circulation features may have a great impact on surface gravity waves. In this case study, we coupled in a one‐way mode the hydrodynamic model Regional Ocean Modeling System (ROMS) and the wave model Simulating WAves Nearshore (SWAN) to study the effect of currents on large wave events (LWEs) produced under the influence of cyclones in south/southeastern Brazil. For the five LWEs studied, chosen due to the distinct importance that current‐to‐wave effects had for the period, the results indicate that the addition of currents on the wave model improved the accuracy of the peaks of significant wave height, generally increasing them (by as much as 27%). The increase in wave height occurred mainly near the shelf edge and slope, where the southwestward‐flowing Brazil Current opposes the dominant direction of cyclone‐generated waves (usually from S/SE to S/SW). Modulation of wave height by currents in the subinertial band explained up to 95% of the total variance of the difference between results with and without ocean currents, and this band was largely related to the Brazil Current. Its near‐inertial counterpart explained up to 22% of the total variance and was primarily due to near‐inertial currents in the region. This study provides, for the first time, conclusive evidence that wave‐current interaction can impact LWEs in south/southeastern Brazil.

Formulation of parameter limit values for the operation of a large concrete gravity dam

This study presents a coupled thermal-structural finite element analysis of a large concrete gravity dam in Bulgaria for exploring the dam response under different actual load combinations. The loads applied to the structure are caused by varying water level in the reservoir and ambient temperature typical for the respective seasons. The developed computational model was calibrated with real plumb measurements. Based on the performed analyses in the ANSYS environment, key limit values for the horizontal displacements measured by the plumbs in the dam as possibly caused by extreme combinations of ambient temperature and water level are formulated for further improvement of the dam operation.