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Journal articles on the topic 'Gravity Hinge'
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1
Kim, Hyo Young, Jung Jae Kim, Da Hoon Ahn, Dae Gab Gweon, Chan Gon Park, and Dong Pyo Hong. "Analysis of a 3-DOF Rotationally Symmetric Hinge." Applied Mechanics and Materials 284-287 (January 2013): 597–600. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.597.
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Flexure hinges have been widely used as mechanisms for high precision positioning stages that have a micrometer or nanometer resolution. This paper describes the analysis of a 3-DOF rotationally symmetric hinge for the vertical mask aligner stage. The vertical mask aligner stage was designed to overcome the bending of masks by gravity. In order to align the mask and the wafer, the vertical mask aligner stage has one linear motion and yaw rotating motions (Z, Θx, Θy). The new vertical mask aligner stage will try to use rotationally symmetric hinges. These rotationally symmetric hinges would act as guide mechanisms. However, the exact 6-DOF stiffness analysis of the rotationally symmetric hinge did not use these hinges as guide mechanisms. Therefore, this paper focuses on the stiffness analysis of the rotationally symmetric hinges.
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Fenwick, Richard, Raad Dely, and Barry Davidson. "Ductility demand for uni-directional and reversing plastic hinges in ductile moment resisting frames." Bulletin of the New Zealand Society for Earthquake Engineering 32, no. 1 (March 31, 1999): 1–12. http://dx.doi.org/10.5459/bnzsee.32.1.1-12.
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In a major earthquake the beams in moment resisting frames may develop either reversing or unidirectional plastic hinges. The form of plastic hinge depends upon the ratio of the moments induced by the gravity loading to those induced by the seismic actions. Where this ratio is low the plastic hinges form at the ends of the beams and the sign of the inelastic rotation changes with the direction of sway. These are reversing plastic hinges, and the magnitude of the rotation that they sustained is closely related to the inter-storey displacement. However, when the moment ratio exceeds a certain critical value, unidirectional plastic hinges may form. In this case negative moment plastic hinges develop at the column faces and the positive moment plastic hinges form in the beam spans. As the earthquake progresses the positive and negative inelastic rotations accumulate in their respective zones so that peak values are always sustained at the end of the earthquake. With this type of plastic hinge no simple relationship exists between inter-storey drift and inelastic rotation.
Several series of time history analyses have been made to assess the relative magnitudes of inelastic rotation that are imposed on the two forms of plastic hinge. It is found that with design level earthquakes typically the unidirectional plastic hinge is required to sustain 21/ 2 to 4 times the rotation imposed on reversing plastic hinges, with the curvature ductilities ranging up to 140. These values are appreciably in excess of the values measured in tests using standard details. This indicates that in structures where unidirectional plastic hinges may form, the design displacement ductility and or the allowable inter-storey drift should be reduced below the maximum values currently permitted in the New Zealand codes. The problems associated with the formation of unidirectional plastic hinges can be avoided by adding positive moment flexural reinforcement in the mid regions of the beams. By this means the potential positive moment plastic hinges can be restricted to the beam ends.
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Saenkhum, Nattapon, and Tassanai Sanponpute. "The improvement of an elastic hinge-type torque standard machine in NIMT." ACTA IMEKO 8, no. 3 (September 30, 2019): 36. http://dx.doi.org/10.21014/acta_imeko.v8i3.668.
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<p class="Abstract" align="left">The National Institute of Metrology of Thailand’s (NIMT) strain-controlled elastic hinge-type torque standard machine was designed to cover a measuring range of 1 N·m to 1 kN·m. The elastic hinge was used both at the fulcrum and the hanger of the lever arms. The designed elastic hinge’s thickness, 0.50 mm, caused a higher stiffness than a sheet metal plate of other types of torque machines. The bending moment of all elastic hinges affected the sum of the torque signal on the lever arm that was used to observe the balancing of the lever. The residual torque sensitivity, which was no better than 0.20 mN·m, significantly affected the uncertainty of the low-range torque realisation.</p><p class="Abstract">The calibration and measurement capabilities of the machine were 0.010 % (<em>k</em> = 2) in the measurement range of 10 N·m to 1 kN·m and 0.030 % (<em>k</em> = 2) in the measurement range of 1 N·m to 10 N·m. In the transducer calibration, the influence of the random bending moment of the elastic hinge affected the repeatability, reproducibility, and linearity of the low torque measurements. The cause of the bending moment of the elastic hinges was a result of the deviation of the centre of gravity (CG) of the weight on the pan from the reference line. To improve CMCs, separate signal calibrations were selected for this experiment i.e. the left hinge, the right hinge, and the fulcrum. The torque in each signal calibration was combined by software and was used to correct the calibration value of the torque.</p>
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GABRIELE GIONTI, S. J. "SOME CONSIDERATIONS ON DISCRETE QUANTUM GRAVITY." International Journal of Geometric Methods in Modern Physics 09, no. 02 (March 2012): 1260013. http://dx.doi.org/10.1142/s0219887812600134.
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Recent results in Local Regge Calculus are confronted with Spin-Foam Formalism. Introducing Barrett–Crane Quantization in Local Regge Calculus makes it possible to associate a unique Spin jh with an hinge h, fulfilling one of the requirements of Spin-Foam definition. It is shown that inter-twiner terms of Spin-Foam can follow from the closure constraint in Local Regge Calculus.
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Hassan, Soha, Mohamed Sultan, Mohamed Sobh, Mohamed S. Elhebiry, Khaled Zahran, Abdelaziz Abdeldayem, Elsayed Issawy, and Samir Kamh. "Crustal Structure of the Nile Delta: Interpretation of Seismic-Constrained Satellite-Based Gravity Data." Remote Sensing 13, no. 10 (May 15, 2021): 1934. http://dx.doi.org/10.3390/rs13101934.
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Interpretations of the tectonic setting of the Nile Delta of Egypt and its offshore extension are challenged by the thick sedimentary cover that conceals the underlying structures and by the paucity of deep seismic data and boreholes. A crustal thickness model, constrained by available seismic and geological data, was constructed for the Nile Delta by inversion of satellite gravity data (GOCO06s), and a two-dimensional (2D) forward density model was generated along the Delta’s entire length. Modelling results reveal the following: (1) the Nile Delta is formed of two distinctive crustal units: the Southern Delta Block (SDB) and the Northern Delta Basin (NDB) separated by a hinge zone, a feature widely reported from passive margin settings; (2) the SDB is characterized by an east–west-trending low-gravity (~−40 mGal) anomaly indicative of continental crust characteristics (depth to Moho (DTM): 36–38 km); (3) the NDB and its offshore extension are characterized by high gravity anomalies (hinge zone: ~10 mGal; Delta shore line: >40 mGal; south Herodotus Basin: ~140 mGal) that are here attributed to crustal thinning and stretching and decrease in DTM, which is ~35 km at the hinge zone, 30–32 km at the shoreline, and 22–20 km south of the Herodotus Basin; and (4) an apparent continuation of the east-northeast–west-southwest transitional crust of the Nile Delta towards the north-northeast–south-southwest-trending Levant margin in the east. These observations together with the reported extensional tectonics along the hinge zone, NDB and its offshore, the low to moderate seismic activity, and the absence of volcanic eruptions in the Nile Delta are all consistent with the NDB being a non-volcanic passive margin transition zone between the North African continental crust (SDB) and the Mediterranean oceanic crust (Herodotus Basin), with the NDB representing a westward extension of the Levant margin extensional transition zone.
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Kobayashi, Ryosuke, Shinitiro Nishida, and Shintaro Nakatani. "Study of Mars Rover with Hinge Type Center of Gravity Movement Mechanism." Proceedings of Conference of Chugoku-Shikoku Branch 2018.56 (2018): 1307. http://dx.doi.org/10.1299/jsmecs.2018.56.1307.
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Hasan, Mohammad Nurul, Md Noor Islam, and Salma Begum. "Geophysical interpretation of tectonic features in Bangladesh." Journal of Nepal Geological Society 18 (December 1, 1998): 135–41. http://dx.doi.org/10.3126/jngs.v18i0.32205.
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Bangladesh occupies the major part of the Bengal basin. It is mainly a plain fluvi-dieltaic land. Except the eastern and northeastern Tertiary hilly region, the whole country is covered with thick Quaternary sediments.
Tectonic features in Bangladesh, except the eastern and northeastern hilly structures, are hidden under thick cover of sediments. Gravity anomalies dearly show the locations of major subsurface tectonic features of the country, namely a) Himalayan foredeep, b) Rangpur platform, c) Hinge zone, d) Surma basin and e) Bengal foredeep. Magnetic anomalies and the seismic sections also support the gravity results.
Shape, extent and depth of the tectonic features in Bangladesh are interpreted from geophysical data, particularly from the gravity data supported by available geological and drilling information. Interpretation shows that the Rangpur platform, situated in the northwestern Bangladesh, is the shallowest subsurface tectonic feature in the country. The northern part of the Rangpur platform slopes down to the Himalayan foredeep and the southern part to the Hinge zone. The Surma Basin, containing very thick sediments, lies in north-east corner of the country; and the Bengal foredeep, the most extended tectonic feature, occupies the southern deltaic part of the country. The Fold Belt, the only exposed tectonic feature, lies in the eastern and northeastern hilly region of the country.
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Rezavandi, Arash, and Chung C. Fu. "Response of irregular lightly reinforced concrete frame structures in low seismic zones." Advances in Structural Engineering 20, no. 4 (June 29, 2016): 519–33. http://dx.doi.org/10.1177/1369433216655921.
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This article evaluates the performance of lightly reinforced concrete frames in low seismic zones. The frames under evaluation contain vertical and/or plane irregularities and are designed for gravity loads only. Nonlinear time history analysis using scaled ground motions and pushover procedure as a supplemental method is performed in this study. With the adoption of plastic hinge method, damage levels are addressed according to FEMA 356 definitions. The pivot model is considered for hysteresis behavior. The damage stage and number of formed hinges are classified for the beams and columns. A comparison between models demonstrates while the first story height may suffer minor to moderate damage levels even under low seismic intensity, the severity of damage to the asymmetric plan models can be noticeable. The pushover method results are close to that of time history analysis only for the vertical irregular frames without plane irregularity.
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Xu, Hao, Jinglong Han, Haiwei Yun, and Xiaomao Chen. "Calculation of the Hinge Moments of a Folding Wing Aircraft during the Flight-Folding Process." International Journal of Aerospace Engineering 2019 (September 3, 2019): 1–11. http://dx.doi.org/10.1155/2019/9362629.
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A folding wing morphing aircraft should complete the folding and unfolding process of its wings while in flight. Calculating the hinge moments during the morphing process is a critical aspect of a folding wing design. Most previous studies on this problem have adopted steady-state or quasi-steady-state methods, which do not simulate the free-flying morphing process. In this study, we construct an aeroelastic flight simulation platform based on the secondary development of ADAMS software to simulate the flight-folding process of a folding wing aircraft. A flexible multibody dynamic model of the folding wing structure is established in ADAMS using modal neutral files, and the doublet lattice method is developed to generate aerodynamic influence coefficient matrices that are suitable for the flight-folding process. The user subroutine is utilized, aerodynamic loading is realized in ADAMS, and an aeroelastic flight simulation platform of a folding wing aircraft is built. On the basis of this platform, the flight-folding process of the aircraft is simulated, the hinge moments of the folding wings are calculated, and the influences of the folding rate and the aircraft’s center of gravity (c.g.) position on the results are investigated. Results show that the steady-state method is applicable to the slow folding process. For the fast folding process, the steady-state simulation errors of the hinge moments are substantially large, and a transient method is required to simulate the flight-folding process. In addition, the c.g. position considerably affects the hinge moments during the folding process. Given that the c.g. position moves aft, the maximum hinge moments of the inner and outer wings constantly increase.
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Samimi, Razieh, and Seyed Rasoul Mirghaderi. "Buckling Behavior of Through-Plates under Gravity Loads." Applied Mechanics and Materials 105-107 (September 2011): 2183–87. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.2183.
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Due to the development in the construction and building industry in recent years, numerous methods for safer, easier and more economical design of structures have been studied.Because of the high bi-axial bending capacity and high compressive strength of hollow structural sections, these sections are considered as a popular alternative by designers. Supporting the panel zone demands in the columns and occurring the moment hinge at the ends of beam are too available in column with hollow section. One of the major problems in the way of using these sections is lack of appropriate load path to connect beams to them, which ends up using through-plates. Through-plates are plates that pass through column and beams connect to them at their webs. Consequently these plates should have sufficient stiffness in order to provide enough strength. This paper proceeds to study the buckling behavior of through-plates in moment beam to column connections under gravity loads.
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NISHIO, Naoyuki, and Shin-Ichiro NISHIDA. "Study of Mars Exploration Rover get over step by hinge mechanism of center of gravity." Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) 2019 (2019): 2P1—S06. http://dx.doi.org/10.1299/jsmermd.2019.2p1-s06.
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NISHIO, Naoyuki, Shin-Ichiro NISHIDA, and Shintaro NAKATANI. "Study of a Planetary Exploration Rover with a Hinge-type Center-of-gravity Shift Mechanism." TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 19, no. 4 (2021): 469–76. http://dx.doi.org/10.2322/tastj.19.469.
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Adebar, Perry, Poureya Bazargani, James Mutrie, and Denis Mitchell. "Safety of gravity-load columns in shear wall buildings designed to Canadian standard CSA A23.3." Canadian Journal of Civil Engineering 37, no. 11 (November 2010): 1451–61. http://dx.doi.org/10.1139/l10-075.
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It has been a Canadian code requirement for 25 years to check whether concrete gravity-load columns can tolerate the building deformations due to the design earthquake; but the way this has typically been done using linear analysis significantly underestimates the seismic demands on gravity-load columns. Concern about the safety of gravity-load columns over the plastic hinge height of concrete shear walls, particularly elongated wall-like gravity-load columns, has resulted in new design requirements in Update No. 3 of Canadian Standard Association (CSA) A23.3–04 issued in August 2009. The current paper provides the background to these new requirements. If nonlinear analysis is not done, closely spaced seismic hoops shall be provided in all columns and walls that support gravity loads, and these members shall meet the same limit on maximum compression strain depth as concrete shear walls. The results of nonlinear analyses were used to validate this simple design rule, and to investigate factors that increase seismic demands on gravity-load columns such as diagonal cracking of concrete shear walls, localized damage of columns from cover spalling and bar buckling, and larger first storey heights. Nonlinear analysis has shown that 2.4 m (8 ft) long columns can lose over 50% of their axial load carrying capacity at an inelastic drift ratio of only 1%.
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Li, Zhi Lai. "Structural Design of Large Aperture Rectangular Mirror for Space Telescope." Applied Mechanics and Materials 256-259 (December 2012): 855–58. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.855.
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Structural design of large aperture mirror is one of the key technologies for space telescope development. To meet the requirements of high stiffness, strength and thermal dimensional stability, some factors such as support scheme, materials selection, lightweight design and flexible support design were taken into account. The three supports location of the mirror was determined according to the modal analytical solution. By adjusting the parameters of flexure hinge, influences of gravity, assembly stress and thermal stress on the mirror were reduced obviously. Finite element analysis (FEA) results indicate that the surface accuracy reach to rms10.2nm and 10.8nm under the gravity along optical axis direction and 5°C uniform temperature rise respectively, the fundamental frequency of the mirror component is 268Hz. Dynamics test shows that the first order natural frequency is 256Hz, which shows an error less than 5% compared to FEA results.
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Wen, Zhao Dong, Ming Yan, and Lei Zhang. "Motion of Transverse Shock Tester Guided by Parallelogram Mechanism." Applied Mechanics and Materials 716-717 (December 2014): 590–94. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.590.
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The transverse shock tester is an important device to assess the shock resistance ability of ship equipments. Because of the shock point and the gravity center of the tester are not on the same horizontal, the device may generate huge overturning moment. We adopt the finite element method to do the dynamics analysis of the transverse shock tester, using the parallelogram mechanism as its guide device, to analysis its output waveform and other problems, and find: it will appear saw-tooth acceleration waveform result from the oscillation caused by the overturning moment during the impact process; the oscillation will greatly increases the hinge load--changed following the oscillation amplitude periodically--of the parallelogram mechanism; the hinge inner friction almost has no effect on the impact tester movement or the output waveform. From the above statements, we can see that the parallelogram mechanism can not only share the overturning moment generated by the transverse impact, but also can ensure to get the desired output waveform, thus it suits to be used as the guide device of the transverse shock tester.
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Gao, Dengliang, Emily Roberts, Connor Geiger, and Peter Sullivan. "Acadian detachment and wrench faults in central Pennsylvania: Implications for the Marcellus Shale reservoir integrity and gas productivity in the hinge of the Pennsylvania salient." Interpretation 8, no. 1 (February 1, 2020): T151—T165. http://dx.doi.org/10.1190/int-2019-0110.1.
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High-quality 3D seismic data in Clearfield County, central Pennsylvania, reveal subsurface structural details of regional flat-top, box-shaped folds, convergent reverse faults, and cross-regional lineaments in the hinge of the Pennsylvanian salient. Cross-stratal variations in structural relief, bed curvature, and seismic facies indicate that the deformational intensity increases from below the Salina (Upper Silurian) to the Onondaga (Middle Devonian) and then decreases from the Onondaga to the Elk (Upper Devonian). The pre-Onondaga isochron thickness sees an increasing trend but the post-Onondaga isochron thickness sees a decreasing trend on the anticlinal axes. The seismically imaged subsurface structures are consistent with outcrop and topographic observations, wireline and formation microimager (FMI) logs, and gravity and magnetic intensity measurements. The Marcellus Shale (Middle Devonian) gas exploration and production data indicate that the operational activity and gas productivity drop significantly in Clearfield County and other counties in the hinge of the Pennsylvanian salient. We interpret that the regional folds and faults and cross-regional lineaments are detachment and wrench faults that were most likely caused by gravitational sliding above the Salina (salt) during the Acadian (Middle Devonian-Early Mississippian). We infer that the co-occurrence of the regional and the cross-regional faults, particularly the cross-regional wrench faults, might have had a significant impact on the Marcellus Shale reservoir integrity and gas productivity in the hinge of the Pennsylvania salient. These observations and interpretations demonstrate the dynamic interplay among tectonic deformation, syntectonic deposition, and shale gas retention, thus entailing significant geologic, economic, and environmental implications in the Appalachian Basin.
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Boonmee, Chichaya, Kittipoom Rodsin, and Krissachai Sriboonma. "Gravity Load Collapse Behavior of Nonengineered Reinforced Concrete Columns." Advances in Civil Engineering 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/9450978.
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This paper aims at investigating gravity load collapse behavior of extremely poor quality reinforced concrete columns under cyclic loading. Such columns were usually constructed by local people and may not be designed to meet any of the standards. It was found that their concrete strength may be as low as 5 MPa and the amount of longitudinal reinforcement may be lower than 1%. This type of column is deliberately defined as “nonengineered reinforced concrete column,” or NRCC. During earthquake, the gravity load collapse of the NRCC columns caused a large number of death tolls around the world. In this study, four columns as representative of existing NRCC were tested under cyclic loading. The compressive strength of concrete in order of 5 MPa was used to be representative of columns with poor quality concrete. Two axial load levels of 6 and 18 tons were used to study the influence of axial load level on maximum drift at gravity load collapse. To investigate the effect of bar types on drift capacity, 9 mm round bars were used in two specimens and 12 mm deformed bars were used for the rest of the specimens. The maximum drift before gravity load collapse was very dependent on the axial load level. The maximum drift of the specimens subjected to high axial load (18 tons) was extremely low at approximately 1.75% drifts. The use of deformed bars (associated with larger amount of longitudinal reinforcement) caused the damage to severely dissipate all over the height of the columns. Such damage caused columns to collapse at a lower drift compared to those using round bars. Finally, the plastic hinge model was used to predict the maximum drift of the low strength columns. It was found that the model overly underestimates the drift at gravity load collapse.
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Biscarini, Andrea. "Dynamic Effects of Muscle Moment Arm Variation and Heavy External Loads on Hinge Joints." Journal of Applied Biomechanics 19, no. 3 (August 2003): 223–38. http://dx.doi.org/10.1123/jab.19.3.223.
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A two-dimensional model has been developed to predict and explain the effects of the variation of muscle moment arms during dynamic exercises involving heavy external loads. The analytical dependence of the muscle moment arm on the joint angle and on the origin and insertion position was derived for an ideal uniaxial hinge joint, modeling the muscle as a cable following an idealized minimum distance path from the origin to insertion that wraps around the bony geometry. Analytical expressions for the ratios of muscular force and the joint restraining reaction components to the external load weight were deduced, for isokinetic and static exercises, as a function of joint angle, joint angular velocity, and the other geometric parameters defining the model. Therefore, external load weight, joint angular velocity, and constraints to joint range of motion may be adjusted reciprocally in order to control in advance the peak value of the components of the joint load during isokinetic exercises. A dynamic formulation of forearm flexion/extension was solved numerically under the condition of constant biceps force in order to highlight the key role played by the variation in muscle moment arm in preventing injury during lifting of external loads against gravity. For example, our analysis indicates that the mean and peak resultant joint loads decrease by 5% and 14%, respectively, as a result of the change in muscle moment arm that occurs over the range of motion.
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Ferguson, John F., Roger N. Felch, Carlos L. V. Aiken, John S. Oldow, and Holly Dockery. "Models of the Bouguer gravity and geologic structure at Yucca Flat, Nevada." GEOPHYSICS 53, no. 2 (February 1988): 231–44. http://dx.doi.org/10.1190/1.1442458.
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The Bouguer gravity anomaly at Yucca Flat, Nevada, has been modeled by two different techniques: the Cordell‐Henderson and Parker‐Oldenburg methods. The three‐dimensional model has incorporated known density and structural information where possible. These models predict the structural relief on the Cenozoic‐Paleozoic contact to within 150 m or about 15 percent of the actual depth. The three‐dimensional Parker‐Oldenburg method has been found to be efficient in an application involving a large (9000 sample) data base. Numerical stability was ensured by the application of a consistent regularization (a low‐pass filter tuned to suppress the noise‐dominated portion of the data spectrum) of the downward continuation operator. The use of a single regularizing filter for the entire model is not completely satisfactory due to the oversmoothing of shallow regions of the basin. The model is useful in the delineation of the geologic history of the area. Structural features in the model support the hypothesis that regional stress fields rotated significantly during the Tertiary. Major structural elements of the basin are well defined on the Cenozoic‐Paleozoic interface. The principal basin‐bounding fault is the large‐throw Carpetbag fault on the west. This fault was most active during the earliest phases of subsidence. The Yucca fault is seen to be a much smaller feature in the model presented here. The basin is rotated down to the west, with normal hinge faults on the eastern margin.
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Koolstra, J. H. "Dynamics of the Human Masticatory System." Critical Reviews in Oral Biology & Medicine 13, no. 4 (July 2002): 366–76. http://dx.doi.org/10.1177/154411130201300406.
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In this review, the movement characteristics of the human masticatory system are discussed from a biomechanical perspective. The discussion is based upon the three fundamental laws of mechanics applied to the various anatomical structures that are part of the masticatory system. An analysis of the forces and torques applied to the mandible by muscles, joints, articular capsules, and teeth is used to assess the determinants of jaw movement. The principle of relating the interplay of forces to the center of gravity of the lower jaw, in contrast to a hinge axis near its joints, is introduced. It is evident that the muscles are the dominant determinants of jaw movement. The contributions of the individual muscles to jaw movements can be derived from the orientation of their lines of action with respect to the center of gravity of the lower jaw. They cause the jaw to accelerate with six degrees of freedom. The ratio between linear and angular accelerations is subtly dependent on the mass and moments of inertia of the jaw, and the structures that are more or less rigidly attached to it. The effects of articular forces must be taken into account, especially if the joints are loaded asymmetrically. The muscles not only move the jaw but also maintain articular stability during midline movements. Passive structures, such as the ligaments, become dominant only when the jaw reaches its movement boundaries. These ligaments are assumed to prevent joint dislocation during non-midline movements.
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Silva, José Guilherme Santos da, and Breno de Almeida Santos Oliveira. "Evaluation of the nondeterministic dynamic structural response of three-dimensional wind turbine steel towers." Wind Engineering 42, no. 4 (July 11, 2018): 364–77. http://dx.doi.org/10.1177/0309524x18777368.
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This investigation develops an analysis methodology aiming at the evaluation of the nondeterministic dynamic structural response of typical wind turbine supporting steel towers. The study was centered on the evaluation of the dynamic behaviour of an actual MM92 wind turbine tower of 2.1 MW Wind Class III IEC2a and mounted on an 80-m-high steel tower. The developed finite element modelling calibration was based on comparisons to experimental data related to an experimental modal analysis acquired on the wind tower structure. The wind tower dynamic structural response was investigated under gravity loads + rotor forces + nondeterministic wind dynamic loads. The present analysis has shown that the wind turbine first bending vibration mode represents the main peak of energy transfer of the dynamic structural response and this energy transfer becomes larger as the wind velocity is increased. Based on the von Mises stress distribution, it was verified that some regions of the wind tower started to yield but there is no plastic hinge formation in the wind tower sections.
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Li, Wangpeng, Xudong Chen, Hongfan Wang, Andrew H. C. Chan, and Yingyao Cheng. "Evaluating the Seismic Capacity of Dry-Joint Masonry Arch Structures via the Combined Finite-Discrete Element Method." Applied Sciences 11, no. 18 (September 18, 2021): 8725. http://dx.doi.org/10.3390/app11188725.
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The behaviour of dry-joint masonry arch structures is highly nonlinear and discontinuous since they are composed of individual discrete blocks. These structures are vulnerable to seismic excitations. It is difficult for traditional methods like the standard finite element method (FEM) to simulate masonry failure due to their intrinsic limitations. An advanced computational approach, i.e., the combined finite-discrete element method (FDEM), was employed in this study to examine the first-order seismic capacity of masonry arches and buttressed arches with different shapes subjected to gravity and constant horizontal acceleration. Within the framework of the FDEM, masonry blocks are discretised into discrete elements. A finite element formulation is implemented into each discrete element, providing accurate predictions of the deformation of each block and contact interactions between blocks. Numerical examples are presented and validated with results from the existing literature, demonstrating that the FDEM is capable of capturing the seismic capacities and hinge locations of masonry arch structures. Further simulations on geometric parameters and friction coefficient of masonry buttressed arches were conducted, and their influences on the seismic capacities are revealed.
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Johnson, Ronald, Justin Birdwell, and Tracey Mercier. "Controls on organic matter distributions in Eocene Lake Uinta, Utah and Colorado." Mountain Geologist 55, no. 4 (December 2018): 177–216. http://dx.doi.org/10.31582/rmag.mg.55.4.177.
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The Green River Formation deposited in Eocene Lake Uinta in the Uinta and Piceance Basins, Utah and Colorado, contains the largest oil shale resource in the world with an estimated 1.53 trillion barrels of oil in place in the Piceance Basin and 1.32 trillion barrels in the Uinta Basin. The Douglas Creek arch, a slowly subsiding hinge-line between the two basins, created separate deep depocenters, one in each basin with shallow water conditions near the crest of the arch. Lake Uinta was a saline lake throughout its history with a lower saline to hypersaline layer (monimolimnion) and an upper less saline layer (mixolimnion). Most of the organic matter in the Green River Formation was derived primarily from algae that lived in the photic zone of the lake and is very hydrogen-rich and oil-prone. In many modern large and deep lakes, rates of organic matter production are highly variable due to differences in nutrient supply. However, cyclonic circulation often leads to winnowing out of organic and mineral matter in the mixolimnion leading to organic matter and fine-grained mineral matter being deposited in increasing amounts toward hydro-dynamically dead zones in the center of the circulation producing concentric bands of increasing organic matter content. Organic matter transport through the dense, hypersaline monimolimnion may have been facilitated by low density organic matter attaching to more dense clay mineral particles. Most of the oil shale intervals deposited in Lake Uinta display similar patterns in their organic matter distributions, increasing in very regular fashion toward the central areas of the lake’s two depocenters. This concentric feature is particularly prominent in the most laminated oil shale zones. Here, we propose that cyclonic circulation was present in Lake Uinta. Each basin appears to have had its own circulation currents, separated by shallow water conditions near the Douglas Creek arch, and one hydrodynamically dead zone in each basin. Sediment gravity flow processes were also very active in some strata of Lake Uinta, leading to the reworking and re-depositing of sediments. Two general types of sediment gravity flows are recognized: (1) organic-rich sediment gravity flows that reworked and may have concentrated organic-rich material closer to the two deep depocenters, and (2) sandstone- and siltstone-rich organic-poor mass movement deposits that originated on marginal shelves. Mass movements could have been triggered by various natural processes and/or possibly by the movement of dense brines that evolved on marginal shelves and moved along the bottom of the water column toward the deep part of the lake. The uppermost, poorly consolidated sediment layer was incorporated in sediment gravity flows as they moved, and in many cases sediment gravity flows scoured down significantly into the more consolidated underlying sediment producing large rip-up clasts of laminated sediments. Truncation of more than 100 ft occurs at the base of a sequence of sediment gravity flows in one well, indicating a significant incised channel. Coarser-grained sediment gravity flows terminated before reaching the lake’s deepest areas, forming thick concentric buildups of organically lean sediment near the base of the marginal slopes. Intervals dominated by organic-rich fine-grained sediment gravity flows have tightly concentric bands of increasing organic matter toward the deepest parts of the lake and can be organically richer than the richest laminated intervals. There is some evidence that the hydrodynamically quiet zones did not always correspond closely to the deepest areas of the lake, extending in some cases into some shallower areas.
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Ramhormozian, Shahab, G. Charles Clifton, Massimo Latour, and Gregory A. MacRae. "Proposed Simplified Approach for the Seismic Analysis of Multi-Storey Moment Resisting Framed Buildings Incorporating Friction Sliders." Buildings 9, no. 5 (May 23, 2019): 130. http://dx.doi.org/10.3390/buildings9050130.
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An innovative, simplified, and accurate model is proposed and developed to enable simplified yet realistic time history analysis of multi-storey buildings with moment resisting connections using friction energy dissipaters in the commonly used structural analysis and design program, SAP2000. The analyses are rapid to undertake, thereby enabling detailed study of the influence of many building system effects on the overall response. This paper presents the outcome of dynamic analysis of a complete 13-storey moment resisting steel building with Sliding Hinge Joints as the beam-column connections, considering the influential self-centring factors such as MRF and gravity columns continuity as well as column base and diaphragm flexibilities. The building is one of the Te-Puni towers, which are structural steel apartment buildings with steel-concrete composite floors, designed according to the low damage design philosophy, built in Wellington, New Zealand in 2008 and which have already been subjected to two significant earthquakes. The key objectives of the research have been to take the design of the 13-storey building and convert that into the proposed simplified model required for time history seismic analysis, to undertake analysis under scaled El-Centro earthquake record, investigate the peak inter-storey drift and the residual drift of the building, and determine the influence of column base rotational stiffness, floor slab out of horizontal plane displacement, type of friction damper, and MRF and gravity column continuity. It is concluded that the response of the building is stable and predictable, as expected, and that the post-earthquake state of the building, particularly from the self-centring point of view, is well within the limits for maintaining operational continuity following an ULS level design earthquake.
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Dooley, Tim P., Michael R. Hudec, Dan Carruthers, Martin P. A. Jackson, and G. Luo. "The effects of base-salt relief on salt flow and suprasalt deformation patterns — Part 1: Flow across simple steps in the base of salt." Interpretation 5, no. 1 (February 1, 2017): SD1—SD23. http://dx.doi.org/10.1190/int-2016-0087.1.
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Passive margins underlain by a salt detachment are typically interpreted as kinematically linked zones of updip extension and downdip contraction separated by a zone of translation above a smoothly dipping base of salt. However, salt flow is affected by the base-of-salt geometry across which it flows, and early-stage gravity gliding induced by basin tilt may be complicated by the presence of salt-thickness changes caused by the pre-existing base-salt relief. We investigate these effects using physical models. Dip-parallel steps generate strike-slip fault zones separating domains of differential downslope translation and structural styles, provided the overburden is thin enough. If the overburden is thicker, it resists breakup, but a change in the structural trend occurs across the step. Steps with mild obliquity to the dip direction produce transtensional and transpressional faults in the cover separating structural domains. Deformation complexity in the overburden increases where base-salt steps strike at a high angle to salt flow, and it is especially dependent on the ratio between the thick ([Formula: see text]) and thin ([Formula: see text]) salt across the step at the base of salt. Where the salt-thickness ratio ([Formula: see text]) is high, basal drag generates major flux mismatches, resulting in a contractional thickening of the salt and associated overburden shortening in thin salt above a base-salt high block. Shortening is transient and superseded by extension as the salt thickening allows the flow velocity to increase. When transitioning off a base-salt high block into a low block, the greater flux within the thick salt results in a monocline with extensional and contractional hinges. Structures are further deformed as they translate through these hinge zones. Our physical models demonstrate that extensional diapirs and compressional fold belts can be initiated anywhere on a slope as the salt accelerates and decelerates across base-salt relief. A fold belt from the Campos Basin, offshore Brazil, is used to illustrate these processes.
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Sampson, Lee M., and Nicholas C. Williams. "The geophysical response of the Goldrush-Fourmile orebody and implications for camp-scale Carlin-type deposit exploration, Cortez District, Nevada." Leading Edge 40, no. 2 (February 2021): 122–28. http://dx.doi.org/10.1190/tle40020122.1.
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Since discovery of the Goldrush and Fourmile deposits, numerous geophysical surveys have been acquired over the footprint of mineralization and surrounding areas to focus exploration. The Goldrush-Fourmile system extends more than 7 km in strike length and averages approximately 300 m wide. Most of the orebody lies more than 300 m below ground surface and continues to depths of more than 900 m. Direct detection of the ore system using geophysical tools is impeded by several factors. The system is relatively flat lying and sits in the hinge of a doubly plunging anticline. This gives the shallowest zones a very small lateral footprint. The ore consists of thin strata-bound zones of silica-sulfide mineralization with a tight alteration selvage. Structural controls along faults are limited, with only small displacements. Strong petrophysical contrasts exist between unaltered rock units. Finally, the terrain is rugged. Resistivity inversions of airborne electromagnetic data show that mineralization sits within a complex zone of resistivity responses. Close to intrusions, the host stratigraphy is resistive. Away from intrusions, the same stratigraphic units show highly variable but commonly very low resistivities. This suggests the possibility of redistribution of carbon around intrusions during premineralization metasomatism. Within the orebody, sulfide content increases conductivity within individual formations related to the distribution of fine-grained sooty pyrite. The geometry of the Red Hill Anticline is imaged as a positive density contrast in the observed gravity and geologically constrained gravity inversions. The positive density contrast represents the gross geophysical signature of denser carbonates within the Paleozoic stratigraphy. Magnetic surveys are crucial for mapping the distribution of igneous rocks and potentially hornfelsed sedimentary rocks. The challenges associated with exploring for deeply buried Carlin mineralization notwithstanding, the application of innovative geophysical tools tuned to assess specific geologic questions, combined with best-practice geologic and geochemical modeling, is helping drive exploration for additional Carlin-type mineralization across the Cortez District.
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Singh, Chandeep, Shitij Kacker, and Sanjiv KS Marya. "Modified Extended Trochanteric Osteotomy." Journal of Postgraduate Medicine, Education and Research 50, no. 2 (2016): 93–95. http://dx.doi.org/10.5005/jp-journals-10028-1199.
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ABSTRACT Trochanteric osteotomy, the most extensile approach, is a valuable tool for difficult primary and revision total hip arthroplasties (THAs). Extended trochanteric osteotomy (ETO) is helpful in revision and extraction of well-fixed cemented as well as uncemented fremoral components, facilitates in cement extraction, and also in enhancing acetabular exposure. Tradional posterolateral ETO is initiated at the posterior aspect of the femur. We describe a modification of ETO by an anterolateral approach. The advantage of this approach is that as it preserves an intact musculo-osseo-muscular sleeve comprising of gluteus medius and minimus, greater trochanter, and vastus lateralis it allows physiological reconstruction of hip's soft tissue envelope and thus prevents proximal migration, nonunion of the osteotomy, and abductor lurch, which are the commonest complications associated with an ETO. Anterolateral exposure of hip joint and anterior fibers of gluteus medius, minimus, and capsule reflected as cuff and limbs of osteotomy are marked, and after completing the osteotomy with the help of osteotomes passed from posterior to anterior, the fragment is hooked open on its anterior muscular hinge. Osteotomy is fixed with the help of three to four cerclage wires depending on length of osteotomy. Full-weight bearing and abduction against gravity are only allowed after confirming radiological union of the osteotomy. How to cite this article Kacker S, Singh C, Marya SKS. Modified Extended Trochanteric Osteotomy. J Postgrad Med Edu Res 2016;50(2):93-95.
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VOLDMAN, GUSTAVO G., JUAN L. ALONSO, LUIS P. FERNÁNDEZ, ALDO L. BANCHIG, GUILLERMO L. ALBANESI, GLADYS ORTEGA, and RAÚL CARDÓ. "Cambrian–Ordovician conodonts from slump deposits of the Argentine Precordillera: new insights into its passive margin development." Geological Magazine 155, no. 1 (October 18, 2016): 85–97. http://dx.doi.org/10.1017/s0016756816000832.
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AbstractThe Los Sombreros Formation represents the western continental margin slope deposits of the Argentine Precordillera, a sub-terrane accreted to Gondwana as part of the Cuyania Terrane in early Palaeozoic times. The age of these gravity-driven deposits is controversial and, therefore, a precise biostratigraphic scheme is essential to reveal the evolution of the continental margin. New conodont samplings along with sedimentological and structural analysis carried out in the Los Sombreros Formation in the La Invernada Range provide clues to its depositional framework. The sedimentary succession is made up of dominantly calciturbidites, carbonate breccias and conglomerates, along with mudstones that represent the pelagic/hemipelagic background sedimentation. It displays hectometric to outcrop-scale slump folds with variable hinge-line orientations and pinch-and-swell structures, evidencing soft-sediment deformation, consistent with a slope to base-of-slope setting. Three limestone samples from this succession include conodonts referable to the pandemicHirsutodontus simplexSubzone of theCordylodus intermediusZone (upper Furongian, Cambrian) and from theMacerodus dianaeZone (upper Tremadocian, Ordovician), implying that a slope connected the shallow-water shelf with a deep-water (oceanic) basin at least since late Cambrian times. The conodont faunas show affinities to coeval assemblages from outer shelf and slope environments around Laurentia yet they are not conclusive to postulate a geographic origin for the Precordillera. The thermal alteration of the conodonts is consistent with sedimentary burial and nappe stacking in this sector of the Precordillera.
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Yi, Chunzhi, Feng Jiang, Chifu Yang, Zhiyuan Chen, Zhen Ding, and Jie Liu. "Reference Frame Unification of IMU-Based Joint Angle Estimation: The Experimental Investigation and a Novel Method." Sensors 21, no. 5 (March 5, 2021): 1813. http://dx.doi.org/10.3390/s21051813.
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Inertial measurement unit (IMU)-based joint angle estimation is an increasingly mature technique that has a broad range of applications in clinics, biomechanics and robotics. However, the deviations of different IMUs’ reference frames, referring to IMUs’ individual orientations estimating errors, is still a challenge for improving the angle estimation accuracy due to conceptual confusion, relatively simple metrics and the lack of systematical investigation. In this paper, we clarify the determination of reference frame unification, experimentally study the time-varying characteristics of reference frames’ deviations and accordingly propose a novel method with a comprehensive metric to unify reference frames. To be specific, we firstly define the reference frame unification (RFU) and distinguish it with drift correction that has always been confused with the term RFU. Secondly, we design a mechanical gimbal-based experiment to study the deviations, where sensor-to-body alignment and rotation-caused differences of orientations are excluded. Thirdly, based on the findings of the experiment, we propose a novel method to utilize the consistency of the joint axis under the hinge-joint constraint, gravity acceleration and local magnetic field to comprehensively unify reference frames, which meets the nonlinear time-varying characteristics of the deviations. The results on ten human subjects reveal the feasibility of our proposed method and the improvement from previous methods. This work contributes to a relatively new perspective of considering and improving the accuracy of IMU-based joint angle estimation.
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Le, Jia-Liang, and Zdeněk P. Bažant. "Mechanics of Collapse of WTC Towers Clarified by Recent Column Buckling Tests of Korol and Sivakumaran." International Journal of Structural Stability and Dynamics 17, no. 09 (October 23, 2017): 1771011. http://dx.doi.org/10.1142/s0219455417710110.
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The previously formulated model of the gravity-driven collapse of the twin towers of the World Trade Center (WTC) on September 11, 2011 was shown to match all the existing observations, including the video record of the crush-down motion of the top part of tower during the first few seconds, the seismically recorded duration of collapse, the size distribution of particles caused by impact comminution of concrete floor slabs, the loud booms due to near-sonic lateral ejection velocity of air and dust, and precedence of the crush-down collapse mode before the crush-up. Nevertheless, different degrees of ductility, fracturing and end support flexibility of WTC columns could lead to an equally good match of these observations and remained uncertain, due to lack of test data. Recently, Korol and Sivakumaran reported valuable experiments that allow clarifying this uncertainty. They revealed that, under the simplifying assumptions of rigid end supports and unlimited ductility (or no fracturing) of unheated columns, the energy dissipation of the WTC columns would have been at maximum 3.5-times as large as that calculated by the plastic hinge mechanism normally considered for small-deflection buckling. This increase would still allow close match of all the aforementioned observations except for the first two seconds of the video. The proper conclusion from Korol and Sivakumaran’s tests, based on close matching of the video record, is that the fracturing of unheated columns and the flexibility of their end restraints must have significantly reduced the energy dissipation in columns calculated under the assumptions of no fracture and no end restraint flexibility.
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Meggett, L. M., and R. C. Fenwick. "Seismic behaviour of a reinforced concrete portal frame sustaining gravity loads." Bulletin of the New Zealand Society for Earthquake Engineering 22, no. 1 (March 31, 1989): 39–49. http://dx.doi.org/10.5459/bnzsee.22.1.39-49.
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To study the behaviour of multistorey building frames under gravity and severe earthquake conditions a reinforced concrete portal frame was constructed. The beam was subjected to constant vertical loads while a cyclic lateral load was applied to the unit. Negative moment plastic hinges formed at the column faces while the positive moment hinges were located in the span. The rotations generated by each inelastic displacement accumulated. This placed high rotational demands on the plastic hinges, which reduced the overall ductile behaviour compared with that observed in typical beam-column sub-assembly tests. The high rotations caused the beam to grow in length.
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Milgrom, Mordehai. "MOND theory." Canadian Journal of Physics 93, no. 2 (February 2015): 107–18. http://dx.doi.org/10.1139/cjp-2014-0211.
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A general account of modified Newtonian dynamics (MOND) theory is given. I start with the basic tenets of MOND, which posit departure from standard dynamics in the limit of low acceleration — below an acceleration constant a0 — where dynamics become scale invariant. I list some of the salient predictions of these tenets. The special role of a0 and its significance are then discussed. In particular, I stress its coincidence with cosmologically relevant accelerations, which may point to MOND having deep interplay with cosmology. The deep-MOND limit and the consequences of its scale invariance are considered in some detail. There are many ways to achieve scale invariance of the equations of motion — guaranteed if the total action has a well-defined scaling dimension. The mere realization that this is enough to ensure MOND phenomenology opens a wide scope for constructing MOND theories. General aspects of MOND theories are then described, after which I list briefly presently known theories, both nonrelativistic and relativistic. With few exceptions, the construction of known, full-fledged theories follows the same rough pattern: they modify the gravitational action; hinge on a0; introduce, already at the level of the action, an interpolating function between the low and high accelerations; and they obey MOND requirements in the two opposite limits. These theories have much heuristic value as proofs of various concepts (e.g., that covariant MOND theories can be written with correct gravitational lensing). But, probably, none points to the final MOND theory. At best, they are effective theories of limited applicability. I argue that we have so far explored only a small corner of the space of possible MOND theories. I then outline several other promising approaches to constructing MOND theories that strive to obtain MOND as an effective theory from deeper concepts, for example, by modifying inertia and (or) gravity as a result of interactions with some omnipresent agent. These have made encouraging progress in various degrees, but have not yet resulted in full-fledged theories that can be applied to all systems and situations. Some of the presently known theories do enjoy a natural appearance of a cosmological-constant-like contribution that, furthermore, exhibits the observed connection with a0. However, none were shown to address fully the mass discrepancies in cosmology and structure formation that are otherwise explained by cosmological dark matter. This may well be due to our present ignorance of the true connections between MOND and cosmology. We have no clues as to whether and how MOND aspects enter nongravitational phenomena, but I discuss briefly some possibilities.
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García‐Abdeslem, J. "Gravitational attraction of a rectangular prism with depth‐dependent density." GEOPHYSICS 57, no. 3 (March 1992): 470–73. http://dx.doi.org/10.1190/1.1443261.
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The gravity effect produced by two and three‐dimensional bodies with nonuniform density contrast has been treated by several authors. One of the first attempts in this direction made by Cordell (1973), who developed a method to compute the gravity effect due to a two‐dimensional prism whose density decreases exponentially with depth. A different approach was proposed by Murthy and Rao (1979). They extended the line‐integral method to obtain the gravity effect for bodies of arbitrary cross‐sections, with density contrast varying linearly with depth. Chai and Hinze (1988) have derived a wavenumber‐domain approach to compute the gravity effect due to a vertical prism whose density contrast varies exponentially with depth. Recently, Rao (1990) has developed a closed expression of the gravity field produced by an asymmetrical trapezoidal body whose density varies with depth following a quadratic polynomial.
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Jacobson, Ted, and Manus Visser. "Spacetime equilibrium at negative temperature and the attraction of gravity." International Journal of Modern Physics D 28, no. 14 (October 2019): 1944016. http://dx.doi.org/10.1142/s0218271819440164.
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We derive the Einstein equation from the condition that every small causal diamond is a variation of a flat empty diamond with the same free conformal energy, as would be expected for a near-equilibrium state. The attractiveness of gravity hinges on the negativity of the absolute temperature of these diamonds, a property we infer from the generalized entropy.
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Guspí, F. "Three‐dimensional Fourier gravity inversion with arbitrary density contrast." GEOPHYSICS 57, no. 1 (January 1992): 131–35. http://dx.doi.org/10.1190/1.1443176.
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The use of variable‐density contrasts in gravity inversion has gained increasing importance in recent years due to the necessity of constructing more realistic models of geophysical structures such as sedimentary basins. Linear, quadratic, and exponential variations, either in the space or in the frequency domain, are the basis of several methods. See, among others, the papers by Granser (1987), Chai and Hinze (1988), Reamer and Ferguson (1989), and Rao et al. (1990). Guspí (1990) used polynomial density‐depth functions for inverting gravity anomalies into 2-D polygons in the space domain.
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Roper, H. "Superposed structures in the Mona Complex at Rhoscolyi Ynys Gybi, North Wales." Geological Magazine 129, no. 4 (July 1992): 475–90. http://dx.doi.org/10.1017/s0016756800019567.
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AbstractThe Bedded Series of the Mona Complex at Rhoscolyn comprises two groups of clastic metasediments: the Holy Island Group, consistingof quartzites, impure psammites and pelites, with well-preserved bedding, is overlain conformably by the New Harbour Group, which is for the most parthomogeneously semi-pelitic without surviving bedding. Both groups have undergone the same two major tectono-metamorphic episodes, but with differing response. In the Holy Island Group the first episode (Dx) produced nearly upright and upward-facing folds (Fx) with an axial planar foliation (Sx), which varies from an anastomosing or rough-spaced cleavage in quartzites to a penetrative phyllitic schistosity in pelites. In the New Harbour Group Dx has generally obliterated original bedding surfaces, replacing them with a composite foliation (Sx) of fine compositional banding and a penetrative schistosity, together with a stretching lineation (Lx), the latter being at a high angle to the Fx axial direction. The Dx structures are attributed to a major episode of compressional tectonics.The structures attributed to the second deformation (Dy) includestrata-bound sets of quartz-filled tension fractures (attributed by most previous authors to an earlier episode), abundant NNW-verging asymmetric folds (Fy) of Sx, and a sporadically developed set of shear fractures which constitute a crenulation cleavage (Sy) axial planar to the folds. It is suggested that all these structures were produced by a single agency. One interpretation is that the observed shear fractures and folded tension fractures correspond fairly closely to and provide a natural analogy of those obtained in the classical simple shear experimentsof Riedel. In this case all the Dy structures can be accounted for by the action of a large-scale simple shear couple (Cy), whose vergence and shallow dip were both towards the NNW. Such a mechanism may imply a gravity-dominated regime of net horizontal extension in a NNW-SSE direction, with extension being less constrained to the north than to the south. J. W. Cosgrove has suggested an alternative interpretation, that all the Dy structures can be explained as reverse kink bands; the simple shear interpretation is here preferred because the angle between Sy and the estimated direction of Pmax during Dy was < 45°; the kink band model would require an angle > 45°.The fact that cleavage vergence boundaries for both Sx and Sy occur close to the hinge zone of the Rhoscolyn Antiform is consistent with either Dx or Dy age for the initiation of this fold. However, when fold limb length (or limb rotation) vergence is considered, the presence of an Fx0 vergence boundary but absence of an Fxy vergence boundary (and by implication of an Fy0 boundary) is consistent with a Dx age but difficult to reconcile with a Dy age.
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Kim, Dong-Yeon, Han-Sol Choi, Jae Hyuk Lim, Kyung-Won Kim, and Juwon Jeong. "Experimental and Numerical Investigation of Solar Panels Deployment with Tape Spring Hinges Having Nonlinear Hysteresis with Friction Compensation." Applied Sciences 10, no. 21 (November 7, 2020): 7902. http://dx.doi.org/10.3390/app10217902.
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In this work, experimental and numerical investigation on the deployment of solar panels with tape spring (TS) hinges showing complex nonlinear hysteresis behavior caused by the snap-through buckling was conducted. Subsequently, it was verified by comparing simulation results by multi-body dynamics (MBD) analysis with test results on ground-based deployment testing considering gravity compensation, termed zero-gravity (Zero-G) device. It has been difficult to predict the folding and unfolding behavior of TS hinges because their moment–rotation relationship showed a nonlinear hysteresis behavior. To realize this attribute, an algorithm that checks the sign of angular velocity of the revolute joints was used to distinguish folding from unfolding. The nonlinear hysteresis was implemented in terms of two path-dependent nonlinear moment–rotation curves with the aid of the expression function (a kind of user subroutine) in MBD software RecurDyn. Finally, it was found that the results of the deployment analysis were in excellent agreement with those of the test when the friction torques of the revolute joints were properly identified by an inverse analysis with the test frames, thus validating the MBD model.
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Bahaadini, Reza, Ali Reza Saidi, and Mohammad Hosseini. "Flow-induced vibration and stability analysis of carbon nanotubes based on the nonlocal strain gradient Timoshenko beam theory." Journal of Vibration and Control 25, no. 1 (August 23, 2018): 203–18. http://dx.doi.org/10.1177/1077546318774242.
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A nonlocal strain gradient Timoshenko beam model is developed to study the vibration and instability analysis of the carbon nanotubes conveying nanoflow. The governing equations of motion and boundary conditions are derived by employing Hamilton’s principle, including the effects of moving fluid, material length scale and nonlocal parameters, Knudsen number and gravity force. The material length scale and nonlocal parameters are considered, in order to take into account the size effects. Also, to consider the small-size effects on the flow field, the Knudsen number is used as a discriminant parameter. The Galerkin approach is chosen to analyze the governing equations under clamped–clamped, clamped–hinged and hinged–hinged boundary conditions. It is found that the natural frequency and critical fluid velocity can be decreased by increasing the nonlocal parameter or decreasing the material length scale parameter. Furthermore, it is revealed that the critical flow velocity does not affected by two size-dependent parameters and various boundary conditions in the free molecular flow regime.
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Karlov, A. E., A. A. Postolny, A. V. Fedorov, and S. F. Jatsun. "Simulation of an Exoskeleton with a Hybrid Linear Gravity Compensator." Proceedings of the Southwest State University 24, no. 3 (December 6, 2020): 66–78. http://dx.doi.org/10.21869/2223-1560-2020-24-3-66-78.
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Purpose of research. Development of a mathematical model of an exoskeleton equipped with a hybrid linear gravity compensator (HLGC), dynamic analysis on the example of a typical exoskeleton application scenario (in the process of lifting a load), obtaining time patterns of changes in system parameters, including electric drive torques allowing assessment of power plan power consumption and energy efficiency. The article deals with the challenging issue of improving the efficiency of the exoskeletal suit by means of HLGC. The use of a hybrid approach makes it possible to increase the efficiency of assisting the exoskeletal suit when performing various technological operations, for example, when lifting a load, when tilting and holding. Methods. When developing a mathematical model, an original approach was used to form the motion trajectory of the exoskeleton sectors during operation, based on the use of seventh-order polynomials. The paper uses a mathematical model represented by a system of second-order differential equations that connects the moments acting on the operator and the exoskeleton, the angular accelerations of the operator's back and the exoskeleton. Results. During numerical simulation, time diagrams of changes in system parameters, angles of rotation of exoskeleton hinges, moments that occur in a hybrid LGC, as well as graphs of current consumption of engines when performing lift and tilt with a load are obtained. Conclusion. In the course of the research, a kinematic model of an exoskeleton suit equipped with a GLGC was developed, second-order differential equations describing the dynamic behavior of the electromechanical system were written, and numerical simulation was performed to estimate the forces and energy consumption in the exoskeleton hinges and the drive of the hybrid linear gravity compensator.
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Montuori, R. "The Influence of Gravity Loads on the Seismic Design of RBS Connections." Open Construction and Building Technology Journal 8, no. 1 (December 31, 2014): 248–61. http://dx.doi.org/10.2174/1874836801408010248.
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Connections with Reduced Beam Section (RBS) have been investigated in the last 20 years both from an analytical point of view and from an experimental point of view. Several experimental tests demonstrated that RBS connections designed according to themost modern seismic codes are able to obtain the desired goal: the protection of the connection due to the yielding of the adjacent RBS. But in all the past researches and experimental tests the role that vertical loads can play was neglected or not properly accounted for. This study proposes a new procedure for accurately computing the relation between RBS location, vertical load and amount of section reduction for ensuring that plastic hinges develop in the reduced sections or in a reduced section and in an intermediate section of the beam.
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RUANGRASSAMEE, ANAT, and ARCHAWIN SAWAROJ. "SEISMIC ENHANCEMENT OF REINFORCED-CONCRETE COLUMNS BY REBAR-RESTRAINING COLLARS." Journal of Earthquake and Tsunami 06, no. 03 (September 2012): 1250015. http://dx.doi.org/10.1142/s1793431112500157.
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When reinforced-concrete columns are subjected to lateral cyclic loading, columns usually suffer failures at plastic hinges. If the buckling of longitudinal reinforcements at plastic hinges can be prevented or delayed, columns are expected to carry gravity loads at a higher ductility level. In this study, the rebar-restraining collar (RRC) was developed to improve the post-buckling behavior of longitudinal reinforcements. The behavior was investigated under monotonic loading tests of reinforcing bars with the RRCs and the cyclic loading tests of two reinforced-concrete bridge columns with and without RRCs. From the monotonic loading test, it was found that the RRCs significantly improved the post-yielding behavior of longitudinal reinforcing bars. The ductility and energy dissipation of longitudinal reinforcing bars with RRCs was significantly higher than that of the bare bar. Then, cyclic loading tests of two reinforced-concrete bridge columns were conducted. The cross section of columns was 0.4 m × 0.4 m, and the effective height was 2.15 m. The ratio of longitudinal reinforcing bars was 0.0123, and the volumetric ratio of transverse reinforcement was 0.00424. The column with RRCs did not have buckling of longitudinal reinforcements and had the ductility enhancement of about 17%, comparing to the column without RRCs. One evident benefit of using the RRCs is to control damage at plastic hinges of columns. Hence, the repair cost of columns after an earthquake can be reduced.
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Peloso, Simone, Chiara Casarotti, Filippo Dacarro, and Giuseppe Sinopoli. "Response of an Existing Two-Storey RC Frame Designed for Gravity Loads: In Situ Pushover Tests and Numerical Analyses." Buildings 10, no. 12 (December 4, 2020): 227. http://dx.doi.org/10.3390/buildings10120227.
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The purpose of the research was to study the response of existing constructions, designed for gravity loads only in the South of Italy, more precisely in the Sicily Region. The building is an existing two-story reinforced concrete structure, built in the ‘80s. In order to design the test, numerical study on the structure has been conducted, using information reported on original design drawings or derived by in situ geometric and material investigation. A number of numerical models and pushover analyses of the structure have been carried out, in order to account for the uncertainties related to possible different responses. The numerical analyses aimed at estimating the capacity of the structure in terms of both force and displacement, the ductility reserve, and the most likely sequence of formation of plastic hinges. The pseudo-static cyclic test was designed to push and pull the building in one direction at increasing displacement levels, up to a drift of about 2%. At the end of the test, the infill panels were completely collapsed. Beams, columns, and joints showed plastic hinges and shear failures in different parts of the structure, with spread spalling of the concrete. Numerical and experimental results were found in fair agreement.
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Zheng, Guo Xing. "Research on Multi-Cup Uniform Flow Gravity Sedimentation Single Well Injection-Production Technique." Applied Mechanics and Materials 341-342 (July 2013): 534–39. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.534.
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When the oilfield enters the hing water cut stage, the mining faces the problem that the oil-gas gathering system energy consumption reduction needs to decrease produced water and water injection. This paper proposes a novel multi-cup uniform flow gravity sedimentation single well injection-production technique. The downhole oil-water separator separates oil from water. The separated water is directly reinjected into the injection layer. Higher oil content of oil-water mixture is lifted up to the ground. The water injection and oil production in the production wellbore are simultaneous. This paper also designs a crown-like sedimentation cup structure. The experiment shows that the optimum structure of crown oil-water separator is cylindrical with 30 inclination, 12 edges and one partition baord on the tip at the bottom of corrugated shape. Produced liquid contains water 95 percent; efficiency can be increased more than three times by using multi-cup uniform flow gravity sedimentation separator.
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Lin, Chao, Pingyang Li, Zhonglei Shen, and Jiang Yu. "Characteristic analysis of a micro-/nanopositioning stage with coupling errors by the gravity." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 16 (May 20, 2019): 5860–73. http://dx.doi.org/10.1177/0954406219850592.
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The piezo-actuated micro-/nanopositioning stages are often used in the current precision engineering applications, and the coupling deformation under the gravity of the stage is critical to error analysis. Considering the torsional deformation and bending deformation of the flexure hinges, the coupling error’s analytical model of the positioning stage along the Z-axis is derived by using the virtual work principle and the elastic beam theory. The performance of the proposed theoretical model is analyzed and verified by the comparison between two common materials, and the quantities of the piezoelectric actuators are also analyzed with the impact on the coupling deformation of the stage along the Z-axis. Through the comparison and analysis of theoretical results, simulation results and experimental results, the maximum error between finite element analysis and experimental results is 11.43%, with the rest fluctuates within 10%, which proves the correctness of the theoretical model. It is concluded that gravity generated by the workload and the stage does have an influence on the coupling deformation along the Z-axis of the micro-/nanopositioning stage. It cannot be ignored in the analysis and consideration of the positioning stage.
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Kammerer, J., S. Lacour, T. Stolker, P. Mollière, D. K. Sing, E. Nasedkin, P. Kervella, et al. "GRAVITY K-band spectroscopy of HD 206893 B." Astronomy & Astrophysics 652 (August 2021): A57. http://dx.doi.org/10.1051/0004-6361/202140749.
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Context. Near-infrared interferometry has become a powerful tool for studying the orbital and atmospheric parameters of substellar companions. Aims. We aim to reveal the nature of the reddest known substellar companion HD 206893 B by studying its near-infrared colors and spectral morphology and by investigating its orbital motion. Methods. We fit atmospheric models for giant planets and brown dwarfs and perform spectral retrievals with petitRADTRANS and ATMO on the observed GRAVITY, SPHERE, and GPI spectra of HD 206893 B. To recover its unusual spectral features, first and foremost its extremely red near-infrared color, we include additional extinction by high-altitude dust clouds made of enstatite grains in the atmospheric model fits. However, forsterite, corundum, and iron grains predict similar extinction curves for the grain sizes considered here. We also infer the orbital parameters of HD 206893 B by combining the ~100 μas precision astrometry from GRAVITY with data from the literature and constrain the mass and position of HD 206893 C based on the Gaia proper motion anomaly of the system. Results. The extremely red color and the very shallow 1.4 μm water absorption feature of HD 206893 B can be fit well with the adapted atmospheric models and spectral retrievals. By comparison with AMES-Cond evolutionary tracks, we find that only some atmosphericmodels predict physically plausible objects. Altogether, our analysis suggests an age of ~ 3–300 Myr and a mass of ~ 5–30 MJup for HD 206893 B, which is consistent with previous estimates but extends the parameter space to younger and lower-mass objects. The GRAVITY astrometry points to an eccentric orbit (e = 0.29−0.11+0.06) with a mutual inclination of <34.4 deg with respectto the debris disk of the system. Conclusions. While HD 206893 B could in principle be a planetary-mass companion, this possibility hinges on the unknown influence of the inner companion on the mass estimate of 10−4+5 MJup from radial velocity and Gaia as well as a relatively small but significant Argus moving group membership probability of ~ 61%. However, we find that if the mass of HD 206893 B is <30 MJup, then the inner companion HD 206893 C should have a mass between ~ 8–15 MJup. Finally, further spectroscopic or photometric observations at higher signal-to-noise and longer wavelengths are required to learn more about the composition and dust cloud properties of HD 206893 B.
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Grossi, Eleonora, Matteo Zerbin, and Alessandra Aprile. "Advanced Techniques for Pilotis RC Frames Seismic Retrofit: Performance Comparison for a Strategic Building Case Study." Buildings 10, no. 9 (August 28, 2020): 149. http://dx.doi.org/10.3390/buildings10090149.
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Pilotis buildings have widely spread out in developed countries since World War II onwards. From the structural point of view, Pilotis RC frames exhibit substantial lack in ductility capacity and shear resistance localized at the first floor, since they have been mainly realized before the seismic codes’ era. The present study shows the performance comparison of four advanced retrofit techniques when applied to typical Pilotis RC frame designed for gravity loads only according to Italian building code of ‘60s. A preliminary investigation has been performed to select non-linear numerical models suitable to describe the considered RC frame behavior, involving flexural inelastic hinges of RC beams and columns and in-plane axial inelastic hinges of masonry infill panels. Two seismic retrofit projects have been designed at a local level, by strengthening the masonry infilled panels with Fiber Reinforced Cementitious Matrix (FRCM) technique and alternatively by replacing infilled panels with prefabricated panels disconnected from the structure, so that no infill/frame interaction occurs. Two more retrofit projects have been designed at a global level, in order to improve the overall structural performance making use of energy dissipation and, alternatively, base isolation techniques. Nonlinear time history analysis and structural assessment have been carried out for the as-built case as well as for the four retrofit solutions according to Eurocode 8 and Italian Building Code, in order to highlight the structural deficiencies and relative improvements, respectively. Performances offered by the proposed retrofit techniques have been finally compared in terms of structural behavior, expected damage, and economic impact.
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Rácz, Kornelius, Daniel Brown, and Francisco J. Valero-Cuevas. "An involuntary stereotypical grasp tendency pervades voluntary dynamic multifinger manipulation." Journal of Neurophysiology 108, no. 11 (December 1, 2012): 2896–911. http://dx.doi.org/10.1152/jn.00297.2012.
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We used a novel apparatus with three hinged finger pads to characterize collaborative multifinger interactions during dynamic manipulation requiring individuated control of fingertip motions and forces. Subjects placed the thumb, index, and middle fingertips on each hinged finger pad and held it—unsupported—with constant total grasp force while voluntarily oscillating the thumb's pad. This task combines the need to 1) hold the object against gravity while 2) dynamically reconfiguring the grasp. Fingertip force variability in this combined motion and force task exhibited strong synchrony among normal (i.e., grasp) forces. Mechanical analysis and simulation show that such synchronous variability is unnecessary and cannot be explained solely by signal-dependent noise. Surprisingly, such variability also pervaded control tasks requiring different individuated fingertip motions and forces, but not tasks without finger individuation such as static grasp. These results critically extend notions of finger force variability by exposing and quantifying a pervasive challenge to dynamic multifinger manipulation: the need for the neural controller to carefully and continuously overlay individuated finger actions over mechanically unnecessary synchronous interactions. This is compatible with—and may explain—the phenomenology of strong coupling of hand muscles when this delicate balance is not yet developed, as in early childhood, or when disrupted, as in brain injury. We conclude that the control of healthy multifinger dynamic manipulation has barely enough neuromechanical degrees of freedom to meet the multiple demands of ecological tasks and critically depends on the continuous inhibition of synchronous grasp tendencies, which we speculate may be of vestigial evolutionary origin.
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Sobczak, L. W., U. Mayr, and J. F. Sweeney. "Crustal section across the polar continent–ocean transition in Canada." Canadian Journal of Earth Sciences 23, no. 5 (May 1, 1986): 608–21. http://dx.doi.org/10.1139/e86-063.
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The Canadian Arctic Transect extends northwards from the Canadian Shield across a thick (about 18 km) and wide (over 800 km) sedimentary section consisting of four overlapping basins. These overlie a continental crystalline crust that thins from 48 to 8 km towards the Canada Basin. The latter overlies a relatively thin (5 – 10 km thick) oceanic crust below the Arctic Ocean. The calculated gravity effects of the upper sedimentary section were stripped away from the observed gravity anomaly, and the residual anomalies were used to determine the boundaries between sediment and crystalline crust and between crust and mantle. Residual anomalies with short wavelength and steep gradients were used to modify the initial near-surface structural model and to identify zones of evaporite and mafic rocks within the sedimentary rock column.Some interesting results emerge from this analysis: (1) analysis of the gradients of the shelf and slope suggests that shelf subsidence is hinged about a line near the central axis of the Sverdrup Basin; (2) continental crystalline crust thins oceanward from 48 km to 8 km at the transition zone over a distance of 825 km and appears to have stretched from an original width of 543 km, for an apparent stretch factor of about 1.5; (3) sediment thickness is usually inversely related to the crystalline crustal thickness; (4) the mantle below the ocean appears to be less dense than below the continental crust, with an assumed significant vertical density boundary between the two below the continental shelf (transition zone); (5) this analysis supports the concept that evaporites occur along the axis of the Sverdrup Basin, and mafic rocks appear to be concentrated along the flanks of the Sverdrup Basin; and (6) seismicity usually occurs over areas of relatively positive gravity anomalies that are considered to be the result of uncompensated sedimentary loads or mafic igneous intrusions or are areas of uplifted and folded rocks.
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Watts, A. B. "Review of “Gravity and Magnetic Exploration: Principles, Practices and Applications” by W. J. Hinze, R. R. B. Von Frese and A. H. Saad." Marine Geophysical Research 35, no. 4 (April 22, 2014): 423. http://dx.doi.org/10.1007/s11001-014-9222-z.
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Deike, Luc, W. Kendall Melville, and Stéphane Popinet. "Air entrainment and bubble statistics in breaking waves." Journal of Fluid Mechanics 801 (July 19, 2016): 91–129. http://dx.doi.org/10.1017/jfm.2016.372.
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We investigate air entrainment and bubble statistics in three-dimensional breaking waves through novel direct numerical simulations of the two-phase air–water flow, resolving the length scales relevant for the bubble formation problem, the capillary length and the Hinze scale. The dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial scaling arguments. The air entrainment properties and bubble size statistics are investigated for various initial characteristic wave slopes. For radii larger than the Hinze scale, the bubble size distribution, can be described by $N(r,t)=B(V_{0}/2{\rm\pi})({\it\varepsilon}(t-{\rm\Delta}{\it\tau})/Wg)r^{-10/3}r_{m}^{-2/3}$ during the active breaking stages, where ${\it\varepsilon}(t-{\rm\Delta}{\it\tau})$ is the time-dependent turbulent dissipation rate, with ${\rm\Delta}{\it\tau}$ the collapse time of the initial air pocket entrained by the breaking wave, $W$ a weighted vertical velocity of the bubble plume, $r_{m}$ the maximum bubble radius, $g$ gravity, $V_{0}$ the initial volume of air entrained, $r$ the bubble radius and $B$ a dimensionless constant. The active breaking time-averaged bubble size distribution is described by $\bar{N}(r)=B(1/2{\rm\pi})({\it\epsilon}_{l}L_{c}/Wg{\it\rho})r^{-10/3}r_{m}^{-2/3}$, where ${\it\epsilon}_{l}$ is the wave dissipation rate per unit length of breaking crest, ${\it\rho}$ the water density and $L_{c}$ the length of breaking crest. Finally, the averaged total volume of entrained air, $\bar{V}$, per breaking event can be simply related to ${\it\epsilon}_{l}$ by $\bar{V}=B({\it\epsilon}_{l}L_{c}/Wg{\it\rho})$, which leads to a relationship for a characteristic slope, $S$, of $\bar{V}\propto S^{5/2}$. We propose a phenomenological turbulent bubble break-up model based on earlier models and the balance between mechanical dissipation and work done against buoyancy forces. The model is consistent with the numerical results and existing experimental results.