Changes In Eccentricity Research Articles

Nonlinear Dynamic Numerical Analysis of Solid-liquid Separation Rolling Bearing-Rotor System Finite Element Discrete Modeling

Based on a rolling bearing-single disc rotor, centrifugal force is generated due to the influence of unbalanced factors such as rotor eccentric excitation, bearing restraint stiffness, and rotating stator clearance, which leads to the imbalance of the rotor system, resulting in the problem of friction between the rotor and the stator. This paper establishes a dynamic model of a single-disk rotor supported by rolling bearings, and the fourth-order Runge-Kutta numerical integration method is used to solve it. Bifurcation behavior and nonlinear dynamic response at a rotational speed. The results show that the nonlinear dynamic characteristics of the system are significantly different due to changes in elliptic eccentricity, rotational speed, and bearing constraint stiffness; when the rotational speed increases, the system gradually appears bifurcation, quasi-periodic motion, and instability increases. Therefore, reasonable selection of the working speed of the rotor and the gap between the stator and the rotor can reduce the non-periodic vibration caused by the unbalanced force and improve the stability of the system operation.

Environmental and climate evolution in the Southwest USA since the last interglacial deduced from the pollen record from Stoneman lake, Arizona

Long and continuous lake sedimentary records offer enormous potential for interpreting the paleoenvironmental histories of the past and for understanding how terrestrial environments might adapt in the context of current global warming. However, sedimentary records that contain multiple glacial-interglacial cycles are scarce in continental basins. An ∼80 m sediment core was recently obtained from Stoneman Lake (STL), Arizona, containing a unique record of the last ∼1.3 Ma. Here we show a detailed pollen study of the topmost ∼10 m of the record, covering the last climatic cycle since the Last Interglacial period (MIS5-MIS1; last ∼130,000 years = 130 kyr), with the goal of broadening our knowledge of the paleoenvironmental history of the arid North American Southwest in the past. The STL pollen record shows that the MIS5e interglacial was the warmest period of the last 130 kyr. This is deduced by the abundance of pollen types from plants that today exist at lower elevations that occurred around the STL at that time. These include Pinus edulis and other associated low elevation thermophilous plants such as Juniperus, Ambrosia, Amaranthaceae, Asteraceae and Artemisia. Climate cooled rapidly and dramatically at the MIS5-4 boundary, which triggered a displacement of forest species towards lower elevation, causing P. ponderosa to occupy the study area. MIS3 was characterized by relatively warmer climate conditions with 3 prominent climatic oscillations (MIS3a, b and c). The coldest conditions were reached during MIS2 (LGM), when a ∼1000 m displacement towards lower elevations of the subalpine forest species relative to present is observed. This is deduced by the highest abundance of Picea (∼20–25%) and Abies in the STL record, indicating their occurrence in the study area. Warming during the last deglaciation is evidenced by a shift of vegetation towards higher altitudes and the development of a montane forest composed mainly of Pinus ponderosa and Quercus replacing the LGM subalpine species. This montane forest remained abundant throughout the Holocene. This study shows that orbital-scale climate changes (mainly precession and eccentricity changes) forced vegetation and lake-level oscillations, documenting that insolation had a main role in controlling environmental change in this area. Climate projections of enhanced warming predict that P. edulis and Juniperus forest species will occupy the study area in the near future.

Effect of eccentricity with different shape wellbores on the flushing efficiency of drilling fluid filter cake

The effective flushing of a drilling fluid filter cake is crucial for improving the zone isolation of cement sheaths during cementing operations, some studies have researched the flushing law of filter cake in circular wellbore, however, only a few have studied the flushing law and mechanism of elliptical wellbore and the irregularity of elliptical wellbore may lead to the increase of the non-uniformity of filter cake that may result in different flushing results than the circular wellbore. In this study, a filter cake formation and flushing experimental system is developed for circular and elliptical wellbore, and the formation and flushing experiments of drilling fluid filter cake in circular and elliptical wellbore are conducted, the flushing law and mechanism of drilling fluid filter cake in circular and elliptical wellbore are obtained by combining the computational fluid dynamics (CFD) simulation calculation results with the experimental results. The results revealed that the filter cake flushing efficiency of the same drilling fluid and displacement were primarily affected by the thickness of the initial drilling fluid filter cake, shear strength, wellbore shape, wall shear stress and eccentricity, the initial thickness and shear strength were higher, the filter cake flushing efficiency was lower, the wall shear stress of the flushing fluid was higher, the flushing efficiency of the filter cake was higher, and the change in wellbore shape and eccentricity led to an uneven distribution of annular velocity and reduced the flushing efficiency of the filter cake. The method and conclusion enable to gain an understanding for improving the flushing efficiency of the drilling fluid filter cake and forms a basis for the design of flushing fluids in cementing operations.

Experimental and numerical studies on the hot spot stress calculation method for welded CHS X-joints stiffened by internal ring stiffeners

Ring stiffeners are usually used to enhance the strengths of welded hollow section joints, which may change the magnitude and distribution of hot spot stress around intersections related to the fatigue life of the joints. Up to date, there is no relevant research on the hot spot stress and its calculation method for welded CHS X-joints with internal ring stiffeners in combined load cases, causing a lack of confidence in the fatigue design process. Experimental tests including two types of load cases are firstly carried out to provide a reference for the finite element (FE) modeling. FE analysis is conducted to investigate the influence of internal ring stiffeners on hot spot stress, covering a variety of numbers, thicknesses and spacing of internal ring stiffeners. The hot spot stress calculation method is developed. A fatigue test is subsequently conducted. It is shown that the hot spot stress near the intersection region of the ring stiffeners and tubes is relatively large in addition to those at the crowns and saddles. The locations of interest include both traditional locations and intersection locations of ring stiffener contours and tube contours. Setting ring stiffeners can averagely reduce the hot spot stress ranges by 23.6% in chord and 27.8% in brace, respectively. The extended hot spot stress calculation method is verified for the fatigue design of welded CHS X-joints with ring stiffeners. In the subsequent fatigue test, fatigue failure is found at the intersection locations. A dynamic effect is also observed which is related to the change in load eccentricity. The fatigue strength curve specified in CIDECT design guide No.8 could also be applicable to predict the fatigue life of the welded CHS X-joint with ring stiffeners.

Chaotic diffusion of asteroids in the exterior 1:2 mean motion resonance with Mars

ABSTRACT The inner asteroid belt between 2.1 and 2.5 au is of particular dynamical significance because it is the dominant source of both chondritic meteorites and near-Earth asteroids. This inner belt is bounded by an eccentricity-type secular resonance and by the 1:3 mean motion resonance with Jupiter. Unless asteroid perihelia are low enough to allow scattering by Mars, escape requires transport to one of the bounding resonances. In addition Yarkovsky forces are generally ineffective in changing either the eccentricity and/or inclination for asteroids with diameter ≳30 km. Thus, large asteroids with pericentres far from Mars may only escape from the inner belt through large changes in their eccentricities. In this paper, we study chaotic diffusion of orbits near the 1:2 mean motion resonance with Mars in a systematic way. We show that, while chaotic orbital evolution in both resonant and non-resonant orbits increase the dispersion of the inclinations and eccentricities, it does not significantly change their mean values. We show further that, while the dispersive growth is greatest for resonant orbits, at high e the resonance acts to mitigate asteroid scattering by Mars - making the asteroid lifetime in the belt longer than it would have been for a non-resonant orbit. For asteroids of all sizes in both resonant and non-resonant orbits, the changes in eccentricity needed to account for the observations cannot be achieved by gravitational forces alone. The role of resonant trapping in protecting asteroids from encounters with Mars is also analysed.

Enhanced direct ventilation in the subarctic Pacific Ocean during 3.5–2.73 Ma: New evidence of elemental results from ODP Site 882

Ocean ventilation change in the subarctic Pacific Ocean is critical for regulating nutrients, heating, and ocean–atmosphere CO2 exchange. Debate continues over whether direct ventilation in the subarctic Pacific Ocean has reached the deep/bottom oceans on different time scales over the last millions of years. Here, we studied the main and trace elements, including Si, Ca, Ba, Zn, Zr, and Rb, and stable nitrogen isotope signals between 5.5 and 2.5 Ma at Ocean Drilling Program (ODP) Site 882. Our results revealed that weakening of deep/bottom water circulation after 3.5 Ma at ODP Site 882 was strongly linked to slowdown of deep/bottom water ventilation in the Atlantic and Southern Ocean. Element results indicated increase in oxygen content between ~3.5 and 2.73 Ma, supporting the suggestion of North Pacific Deep Water formation. Surface vertical mixing strength varied over a long cycle of ~400 kyr during the Early- to Mid-Pliocene in the northwest subarctic Pacific Ocean, which was linked to sea surface temperature gradient between low- and high- latitude regions caused by solar radiation differences regulated by changes in the Earth's orbital eccentricity.

Modeling and validation of eccentricity effects in fine angle signals of high precision angular sensors

High precision optical angular sensors are extensively used for detection and control of position and velocity in payload rotating mechanisms and spacecraft actuators. The accuracy and thus the performance of the encoder are significantly affected due to installation eccentricity. In this paper, a comprehensive study of the causes of installation eccentricity is done. The apportionment of the resultant eccentricity is attributed to variations in diametrical clearances, doweling error, gluing error of the glass disc and bearing wobble. The effect of eccentricity changes during rotation. A new 3-center variable eccentricity model is introduced which improves upon the existing 2-centered one in previous literature. This new 3-centered model is able to better predict the deviations in the fine angle signals in a practical system due to variable eccentricity effect. The efficacy of the mathematical model was validated through two independent experiments- 1) by analyzing the electrical signals from opposite read-heads and 2) by performing mechanical measurements- both done on an actual sensor assembly. The eccentricity value calculated from the maximum and minimum phase difference of the fine angle signals is able to exactly match with the total phase difference variation over one complete rotation. It is observed that the variation in the phase difference between the fine angle sinusoidal signals given by two opposite read-heads varies as a shifted sine over one complete rotation and not as a symmetric sine as shown in previous literature. The eccentricity value obtained from mechanical measurement and that computed using the 3-centered model was matching within 0.1 µm. Both the experimental results support the effectiveness of the 3-centered model.

Associations between lower limb eccentric muscle capability and change of direction speed in basketball and tennis players.

BackgroundThe ability to perform a quick and rapid change of direction (CoD) is an important determinant of success in a variety of sports. Previous studies have already highlighted that eccentric strength is a dominant predictor of CoD. However, these studies evaluated eccentric strength through a limited number of outcome measures and used small sample sizes.MethodsA total of 196 athletes participated in the study. The aim of our study was to investigate: (1) the correlation between eccentric outcome measures derived from different tests (Nordic hamstring exercise (NHE), countermovement jump (CMJ) and flywheel (FW) squats), (2) the association between eccentric outcome measures and CoD 90°, CoD 180°; and (3) proportion of explained variance in CoD performance.ResultsVery large associations (r = 0.783, p < 0.001) were observed between peak torque during NHE (NHEPT) and force impulse during the eccentric phase of CMJ (CMJFI). Small to moderate correlations were calculated between peak eccentric force in flywheel squats and peak eccentric force in CMJ (r = 0.220–035, p < 0002). All eccentric CMJ outcome measures and NHEPT were reported as moderate negative associations with both CoD tests. Eccentric measures explained 25.1% of the variance in CoD 90° (CMJPF, NHEPT, F0.125 –peak eccentric force during FW squats with 0.125 kg m2 load), while the same outcome measures explained 37.4% of the variance for CoD 180°.ConclusionOur results suggest that different measures of eccentric strength specifically contribute to CoD performance. Therefore, for successful CoD performance, different aspects of eccentric strength training should be considered in testing and training (maximal eccentric strength, eccentric-concentric actions with fast execution).

A graphical method for the analysis of a satellite’s in-orbit breakup through optical observations

The incessant overcrowding of the space around the Earth with new operative satellites is a critical issue in the Space Traffic Management (STM) framework, especially in last years with the beginning of the new space economy. The operative life of the active satellites is seriously endangered by the numerous uncontrolled objects, i.e., the space debris, which populate the outer space. The consequence of an impact between these objects may be catastrophic, as proved by the events in the recent past. In this context, the in-orbit explosions both of dismissed satellites and rockets stages are one of the main causes of space debris generation. For this reason, a suitable observation and detection strategy of the fragments generated by these events is necessary, e.g., by means of optical systems. In this work, the Sapienza Space Systems and Space Surveillance Laboratory (S5Lab) shows the results, by means of a graphical method, of the short-term analysis of the in-orbit explosions that involved the third stage of the Russian rocket FREGAT-SB and the fragmentation of the military Chinese satellite YUNHAI 1–02. In order to approach the study of a fragmentation event, an observation strategy and an analysis method have been developed. The research of fragments was focused on the orbital plane leading to estimation of fragments’ number and their distribution. The measurements obtained through the images were analyzed in order to understand if the objects present in the images are either included in the North American Aerospace Defense Command (NORAD) catalogue or not. The unknowns could be fragments. The next analysis follows the hypothesis of the isotropic explosion confined only on the tangential impulses. In first approximation, only semi-major axis and eccentricity change due to the impulse. Therefore, it is possible to generate a new Two-Line Elements (TLE) for each fragment leading to an association between the impulses and the affected TLEs. A new, simple, and fast analysis method was developed, specifically to improve the impulse association. It consists in a graphical method where it is possible to see the distribution of the fragments with respect to the original body using the angular distance trend between them.

Thermal Management and Dynamic Performance of a Cooler Design for the Supercritical CO2 Turbine Shaft Cooling

This paper presents the results of a numerical study on a supercritical CO2 (SCO2) turboshaft cooling device by considering heat transfer and hydrodynamics. A micro-cooling device with a radius clearance of 50 micron and a nozzle diameter of 4 mm was designed and used to investigate the heat transfer characteristics of a micro-spacing impinging and gas film dynamics. Sixteen nozzles (N = 16) are equally spaced around the shaft in single or double rows. Investigations include journal speed- and eccentricity-dependent forward and cross-coupled force coefficients, and the effects of nozzle layouts and mass flow rate on the heat transfer efficiency. Analysis of the correlation coefficient shows that the gas density in the radial clearance is the dominant factor affecting the convective heat transfer performance, while the fluid velocity is a secondary factor. And the cooling efficiency (mass flow utilization rate) at low cooling pressure (ps &amp;lt; 0.7 MPa) is significantly greater than that at high cooling pressure (ps &amp;gt; 0.7 MP). In addition, considering the structure alone, a dual-row cooler exhibits a higher average Nusselt number, also registers a higher mass flow rate at the same pressure. Once the shaft is heated only one end, the difference in effectiveness between single- and dual-row cooling is not significant, so coolers with a single-row configuration should be preferred. Then, experimental values for the temperature of the heated rotor are provided under specific cooling airflow conditions. Dynamic analysis results show that the force coefficient of the single-row configuration is more dependent on the journal rotation speed and eccentricity ratio, and exhibits a negative direct stiffness coefficient at higher inlet pressure and journal rotation speed. Moreover, cross-coupled terms (stiffness coefficient) generally have a more explicit variation tendency than direct terms, and are more sensitive to changes in shaft speed and eccentricity. Small clearance cooling is a relatively complex technology aimed to improve heat dissipation efficiency in gas cooling devices while minimizing the effect of hydrodynamic pressure. Comparing the gas force coefficients of different journal speeds reveals a drastic increase in the effect of hydrodynamic pressure when the journal is eccentric. The cooler may be considered for operation with compliant support (such as bump foil) to generate additional damping and appropriately compensate for the eccentricity of the rotor.

Influence of Vertical Downward Annulus Eccentricity on Steam-Water Two-Phase Flow Pressure Drop

Concentric dual-tubing steam injection technique is one of the main methods to improve heavy oil recovery efficiency. From field data, it was discovered that hot fluid at high temperature and pressure caused steam injection casing to have elongation strain and “necking” eccentric buckling, and the eccentricity change affected the accurate prediction of steam-water two-phase flow pressure drop in the steam injection casing. This paper established a coupling model for the steam-water two-phase flow pressure drop in vertical downward eccentric annulus and the wellbore heat transfer and developed a mathematical model calculation program, to validate the accuracy of calculating the liquid holdup and pressure gradient of fully eccentric annulus. This revealed the influential law of eccentricity on the annulus steam-water two-phase pressure, dryness, and enthalpy value. The results indicated that when the eccentricity e increased from 0 to 1, the saturation pressure of steam at annulus wellbore bottom increased by 0.265 MPa, and the dryness and enthalpy value decreased by 8.54 × 10−3 and 11.22 kJ kg−1, respectively. Compared to the concentric layout, the eccentrically arranged steam injection inner tube cannot promote the wet steam dryness at annulus wellbore bottom.

Analysis of vitreous opacities in chronic glaucoma by vitreo‐optical coherence tomography imaging

AbstractPurposeTo analyze the vitreous opacities of rat eyes by optical coherence tomography (OCT) in two models of chronic glaucoma. Hyperreflective opacities at the vitreoretinal interface, their dynamics over time (changes in number, size, intensity, eccentricity, and orientation) and as a function of intraocular pressure were analyzed in two different glaucoma models and compared to healthy controls.MethodsImages of the vitreoretinal interface were obtained by OCT and exported as videos (composed of cross‐sectional images acquired by means of 61 b‐scans measuring around 3 mm in length and centred on the optic nerve). These videos were analysed using a custom program implemented in Matlab. The vitreous opacities, closely related to the immune cells, were analysed.ResultsHyperreflective opacities, extrapolated as soma areas, were classified according to their size: isolated cells (&lt;10 μm2), non‐activated cells (10–50 μm2), activated cells (50–250 μm2) and cell complexes (&gt;250 μm2). In glaucoma models, right eyes showed significant increase of total area compared with left non‐induced eyes, and left eyes showed significant increase compared to healthy controls. The physiological number of opacities was 10–20. Glaucoma‐induced right eyes showed a mean of 70 opacities, a specular response between activated cells and non‐activated cells, and a greater variation in intensity in the smallest cells, that showed an early change in orientation compared with physiological eyes.ConclusionsOur method of analyzing vitreous opacities by OCT could serve as a reliable neuroimaging biomarker to detect disease onset and early progression applicable to glaucoma and potentially other neurodegenerative diseases impacting the retina and optic nerve.

중형 유조선의 프로펠러 추력변동이 축 거동에 미치는 영향 연구

The movement of the propeller shaft shows different changes in each condition, such as static, dynamic, and transient, mainly based on changes in propeller eccentricity due to changes in engine load. In general, this contributes to changing the bearing load of the shaft at the after stern tube bearing, and in severe cases causes damage to the stern tube bearing. To prevent this, various research regarding pragmatic designing on shafting system has been carried out focusing on optimize the relative inclination and retain the oil film thickness between the shaft and the stern tube bearing. However, in order to secure the integrity of the support bearing from damage, it is necessary to additionally consider dynamic conditions including transient conditions such as sudden alteration in the stern wake-field. In this context, this study cross validated the effect of propeller shaft movement during starboard turning of a medium range oil tanker at full laden draft using the strain gauge and displacement sensor. As a result of the analysis, it was confirmed that the propeller thrust fluctuation temporarily increased the load on the stern tube bearing.

Changes in the cyclicity and variability of the eastern African paleoclimate over the last 620 kyrs

There is ongoing debate concerning whether or not changes in the eastern African climate, both long-term and short-term, affected the evolution, dispersal, cultural development, and technological innovations of Homo sapiens – and if so, in what way. We present the wavelet spectral analysis results of a ∼620 kyr record of environmental change from the Chew Bahir (CHB) basin in the southern Ethiopian rift, approximately 120 km from the Omo-Kibish fossil locality, which boasts one of the oldest documented appearances of H. sapiens. Our results indicate that the long-term wet-dry changes in the eastern African climate recorded in the CHB sediments were mainly caused by changes in orbital eccentricity, with relatively dry but variable climates occurring during eccentricity minima within the 400 kyr eccentricity cycle, and increased precipitation, interspersed with distinctly dryer phases associated with orbital precession, during eccentricity maxima. Such insolation-forced precipitation changes would have affected the habitat of H. sapiens in the region; the transition from Acheulean to Middle Stone Age (MSA) documented in the Olorgesailie Basin of southern Kenya coincides with a distinct eccentricity minimum with reduced precipitation and repeated abrupt climatic transitions. In contrast, at the time of the subsequent, first documented occurrence of H. sapiens in eastern Africa the climate was distinctly wetter and less variable.

Structure and Dynamics of Curcumin Encapsulated Lecithin Micelles: A Molecular Dynamics Simulation Study

Curcumin is a natural product with potential pharmaceutical applications that can be augmented by drug delivery technology such as nano emulsion. Our study focuses on microscopic structural and dynamics response of curcumin encapsulation in micellar system with lecithin as a natural surfactant under variations of composition and temperature using molecular dynamics (MD) simulations. The results highlight the self-assembly of lecithin micelle, with curcumin encapsulated inside, from initial random configurations in the absence of external field. The variation of composition shows that lecithin can aggregate into spherical and rod-like micelle with the second critical micelle concentration lies between 0.17-0.22 mol dm−3. The radial local density centering at the micelle center of mass shows that the effective radius of micelle is indeed defined by the hydrophilic groups of lecithin molecule and theencapsulated curcumin molecules are positioned closer to these hydrophilic groups than the innermost part of the micelle. The spherical micelle is shown to be thermally stable within the temperature range of 277-310 K without a perceivable change in the spherical eccentricity. The dynamics of micelle are enhanced by the temperature, but it is shown to be insensitive to the variation of lecithin-curcumin composition within the studied range. Simulation results are in agreement with the pattern obtained from experimental results based on particle size, polydispersity index, and encapsulation efficiency.

Fast and accurate estimation of fuel-optimal trajectories to Near-Earth Asteroids

This paper proposes an improved method for the preliminary evaluation of minimum-propellant trajectories to Near-Earth Asteroids (NEAs). The method applies to missions from Earth to asteroids with small eccentricity and inclination. A planar and a plane-change problem can be distinguished. In the planar problem, the solution assumes that multiple burn arcs are performed in correspondence of the apsides of the target asteroid in order to change the initial spacecraft orbit (i.e., Earth’s orbit) into the target one. The number of arcs is established once the time of flight is given (1 burn at each apsis per revolution, 1 revolution per year can be assumed). The length and propellant consumption of each arc to attain the required changes of semi-major axis and eccentricity are computed by a procedure based on Edelbaum’s approximation, which is well-suited to the problem at hand, as eccentricity changes are expected to be small for feasible missions. No numerical integration is required, but only the numerical solution of a three-unknown algebraic system is needed, making the procedure extremely fast. Plane change is taken into account assuming a constant out-of-plane thrust angle during each burn. A previous simple formulation used an averaged thrust effect over one revolution and neglected the fact that plane changes are more effective at the nodes. Several improvements are here introduced, which greatly increase the method accuracy. The influences of the eccentricity change, the angle between the asteroid line of nodes and line of apsides, and the expected length of the arc are considered: In fact, when the eccentricity is small, the thrust arc can be performed at the nodes where the inclination is efficiently changed, with little penalty in the planar maneuver. An efficient plane change is also performed when the angle between the asteroid line of nodes and line of apsides is small and/or the length of the arc is large, because, in this case, the node is comprised in the apsidal burn. A simple corrective formula accounts for this effect. The new method shows remarkable accuracy. The results comparison with solutions obtained with an indirect optimization method for a set of more than 60 NEAs shows a 0.95 correlation coefficient in the propellant masses. The estimation error is below 10% for 75% of the targets, below 15% for 95% of the targets, and always below 20%.

Concentric and Eccentric Force Changes with Elastic Band and Isotonic Heavy Resistance Training: A Randomized Controlled Trial.

BackgroundInclusion of resistance training as part of a general fitness program to improve health, and lower risk of disease and injury is well established. Two common options to improve strength are elastic bands and weights. Comparison between elastic bands (as the sole resistance) to isotonic strengthening for concentric and eccentric strength outcomes following the use of low repetitions/heavy resistance has not been reported.Hypothesis/PurposeThe purpose was to examine the effects of a four-week isotonic low repetitions/heavy resistance strengthening program compared to a low repetitions/heavy resistance elastic band strengthening program on shoulder external rotation, hip abduction, and elbow flexion concentric and eccentric isokinetic force production in college aged untrained females.Study DesignRandomized TrialMethodsTwenty healthy females performed pre-and-post isokinetic (60 degrees/second) concentric/eccentric testing of the elbow flexors, shoulder external rotators, and hip abductors. Participants were randomly assigned to a four-week independent low repetitions/heavy resistance strengthening program performed with either elastic bands or isotonic exercises.ResultsA significant (p < 0.05) effect of time was found for eccentric elbow flexor and concentric and eccentric hip abduction force production in the elastic band group with post-test values greater than pre-test values. A significant (p < 0.05) effect of time was found for elbow flexor concentric and eccentric force production in the isotonic group with post-test values greater then pre-test values. No significant (p>0.05) effect of time was found for shoulder external rotator concentric and eccentric forces for both groups, the isotonic group’s hip abduction concentric and eccentric force production and elastic band group’s elbow flexion concentric force production. No significant effect of intervention (p >0.05) on concentric or eccentric elbow flexors, shoulder external rotators, or hip abductors force production was found, with pre-test and post-test values being similar between groups.ConclusionHealth care practitioners and coaches can consider the prescription of a heavy resistance training program with elastic bands or isotonic exercises for an independent exercise program and expect similar concentric and eccentric muscle force changes.Level of EvidenceLevel 2b

Pressure profile definition over the metal orthotropic deck surface of the decking superstructure ballast pocket from the local load action

The article discusses the interaction issue between the track and the rolling stock to determine the forces working on the track during the passage of a rolling load, and their further distribution through the ballast bed. The study aims to determine the vertical pressure profile working on the orthotropic metal ballast bed slab of the railway superstructure. To determine the load share from the rolling stock transferred from the rails to the cross-sleepers, the rail is represented as a beam of infinite length with one or several concentrated forces. To determine the cross-sleeper stress-strain state, it is considered as a short beam on a cushion course. The article presents the substantiation of the flow mechanics formulas application possibility to the ballast bed. Based on the Boussinesq problem solution, calculation formulas are obtained for determining the pressure along with the ballast bed plate. The results obtained by the proposed method were compared with other authors’ experimental data and the finite element modeling results in the Midas FEA software package. The analysis took into account the design features of the ballast bed plates and the track superstructure on the existing superstructures. A theoretical study of the influence of the sheet of the covering bending stiffness on the pressure profile northing is carried out. The proposed method is applicable for various superstructure and the ballast bed slab, and also takes into account the uneven pressure distribution on the inner and outer rails from the trainload, changes in eccentricity along the length of the structure, different thickness of the ballast bed under the cross-sleepers ends, as well as the effect of centrifugal force.

CORR Insights®: Imbalance in Axial-plane Rotator Cuff Fatty Infiltration in Posteriorly Worn Glenoids in Primary Glenohumeral Osteoarthritis: An MRI-based Study.

CORR Insights®: Imbalance in Axial-plane Rotator Cuff Fatty Infiltration in Posteriorly Worn Glenoids in Primary Glenohumeral Osteoarthritis: An MRI-based Study.

Paleo-ENSO influence on African environments and early modern humans

In this study, we synthesize terrestrial and marine proxy records, spanning the past 620 ky, to decipher pan-African climate variability and its drivers and potential linkages to hominin evolution. We find a tight correlation between moisture availability across Africa to El Niño Southern Ocean oscillation (ENSO) variability, a manifestation of the Walker Circulation, that was most likely driven by changes in Earth's eccentricity. Our results demonstrate that low-latitude insolation was a prominent driver of pan-African climate change during the Middle to Late Pleistocene. We argue that these low-latitude climate processes governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa by increasing resource-rich and stable ecotonal settings thought to have been important to early modern humans.