bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Anthropometrically Parameterized Assistive Lower Limb Exoskeleton
Authors: Laubscher Curt A. , Farris Ryan J. , van den Bogert Antonie J. , Sawicki Jerzy T. 
Published: May 2021

Abstract
This paper presents an innovative design methodology for development of lower limb exoskeletons with the fabrication and experimental evaluation of prototype hardware. The proposed design approach is specifically conceived to be suitable for the pediatric population and uses additive manufacturing and a model parameterized in terms of subject anthropometrics to give a person-specific custom fit. The methodology is applied to create computer-aided design models using average anthropometrics of children 6–11 years old and using anthropometrics of an individual measured by the researchers. This demonstrates that the approach can scale to subject weight and height. A prototype exoskeleton is fabricated, which can actuate the hip and knee joints without restricting hip abduction-adduction motion. In order to test usability of the device and evaluate walking assistance, user effort is quantified in an assisted condition where the subject walks on a level treadmill with the exoskeleton powered. This is compared to an unassisted condition with the exoskeleton unpowered and a baseline condition with the subject not wearing the exoskeleton. Comparing assisted to baseline conditions, torque magnitudes increased at the hip and knee, mechanical energy generated increased at the hip but decreased at the knee, and muscle activations increased in the Vastus Lateralis but decreased in the Biceps Femoris. While the preliminary evidence for walking assistance is not entirely convincing for the tested conditions, the presented design methodology itself is promising as it has been successfully validated through the creation of computer-aided design models for children and fabrication of a serviceable exoskeleton prototype.
Thermodynamic Effects on Pressure Fluctuations of a Liquid Oxygen Turbopump
Authors: Li Deyou , Ren Zhipeng , Li Yu , Miao Boxuan , Gong Ruzhi , Wang Hongjie 
Published: May 2021

AbstractLiquid oxygen turbopumps are an important component of rocket engines. The instability induced by cavitation flow in turbopumps has received considerable attention because of thermodynamic effects. In this study, unsteady numerical simulations of a turbopump with thermodynamic effects were performed. The frequency composition and source of pressure fluctuations in a turbopump were analyzed, and the difference in pressure fluctuations with/without thermodynamic effects was revealed. The results showed that the pressure fluctuations were mainly caused by the interaction between the impeller and diffuser, and the thermodynamic effects slightly increased the amplitudes of the characteristic frequencies. In addition, in the inducer and impeller, three characteristic frequencies (4.089fn, 2.519fn, and 3.238fn, where fn is the rotational frequency) were confirmed. Analyses revealed that the 4.089fn was due to the periodic shedding of cavitation structures on the suction surfaces at the inducer outlet, 2.519fn was induced by the periodic occurrence and collapse of cavitation on the suction surfaces at the impeller inlet; and 3.238fn was from the periodic shedding of cavitation structures on the suction surfaces at the impeller middle blades. The existence of thermodynamic effects decreased the frequency of cavitation shedding and increased the frequency of the periodic occurrence and collapse of cavitation.
Analysis of Gas–Liquid–Solid Three-Phase Flows in Hydrocyclones Through a Coupled Method of Volume of Fluid and Discrete Element Model
Authors: Yu Jiachuan , Luo Xiaotong , Wang Bo , Wu Songhai , Wang Jingtao 
Published: May 2021

Abstract
Liquid–gas–solid three-phase flows in hydrocyclones are studied numerically in this paper by employing a coupled method of the volume of fluid (VOF) and discrete element model (DEM) with Reynolds stress model (RSM) turbulence model. The numerical method is validated by comparing the calculated results to those of experiments published in the literature about the separation of particle flows in hydrocyclones. Since VOF-DEM model could capture the gas–liquid interface of particle flows, the three-dimensional formation process of the air-core together with the formation of the spiral trajectory of particles are depicted for the first time. In addition, the effects of the particle concentration ω (less than 12%) on the air-core formation time Tf and diameter Da are studied systematically, which has not been reported in the literature. The increase of ω has both positive and negative actions on the change of Tf and Da, and the compromises of two kinds of actions generate the valley or peak of the curves of Tf versus ω and Da versus ω, respectively. Moreover, the results for three hydrocyclones with different cone angles are also compared to study the effects of the cylindrical and conical section on the air-core formation and the separation performance of the hydrocyclones. By analyzing the flow fields and the pressure changes inside the hydrocyclones, qualitative explanations of the relevant discoveries are given in this paper. The results will be helpful in the investigation of the multiphase flow behaviors in the hydrocyclone and in the selection of the appropriate hydrocyclone.
The Influence of Gait Stance and Vehicle Type on Pedestrian Kinematics and Injury Risk
Authors: Pak Wansoo , Grindle Daniel , Untaroiu Costin 
Published: May 2021

Abstract
Pedestrians are one of the most vulnerable road users. In 2019, the USA reported the highest number of pedestrian fatalities number in nearly three decades. To better protect pedestrians in car-to-pedestrian collisions (CPC), pedestrian biomechanics must be better investigated. The pre-impact conditions of CPCs vary significantly in terms of the characteristics of vehicles (e.g., front-end geometry, stiffness, etc.) and pedestrians (e.g., anthropometry, posture, etc.). The influence of pedestrian gait posture has not been well analyzed. The purpose of this study was to numerically investigate the changes in pedestrian kinematics and injuries across various gait postures in two different vehicle impacts. Five finite element (FE) human body models, that represent the 50th percentile male in gait cycle, were developed and used to perform CPC simulations with two generic vehicle FE models representing a low-profile vehicle and a high-profile vehicle. In the impacts with the high-profile vehicle, a sport utility vehicle, the pedestrian models usually slide above the bonnet leading edge and report shorter wrap around distances than in the impacts with a low-profile vehicle, a family car/sedan (FCR). The pedestrian postures influenced the postimpact rotation of the pedestrian and consequently, the impacted head region. Pedestrian posture also influenced the risk of injuries in the lower and upper extremities. Higher bone bending moments were observed in the stance phase posture compared to the swing phase. The findings of this study should be taken into consideration when examining pedestrian protection protocols. In addition, the results of this study can be used to improve the design of active safety systems used to protect pedestrians in collisions.
Tribological Investigation of Composite MoS2-TiO2-ZrO2 Coating Material by Response Surface Methodology Approach
Authors: Borgaonkar Avinash , Syed Ismail 
Published: May 2021

Abstract
Molybdenum disulfide (MoS2) is popularly used in tribological applications because of its excellent lubricating properties. However, its performance needs to be further improved. In the present study, an attempt has been made to improve the wear resistance of pure MoS2 coating by incorporating TiO2 and ZrO2 nanoparticles as a reinforcement material into the MoS2 base matrix. The composite MoS2-TiO2-ZrO2 coating was applied onto substrate surface by the bonding technique. The tribological performance of the coated specimens was evaluated by employing various operating conditions (such as wt% of compounding elements, contact pressure, and sliding speed) using pin-on-disc friction and wear test rig. A statistical model was developed to identify the significant factors affecting the friction coefficient (COF) and wear-rate of the composite coating material. The design of experiment (DOE) was formulated by response surface methodology (RSM) approach to cut down the number of experiments and to develop a mathematical model between the key process parameters such as wt% of compounding elements, contact pressures, and sliding speeds. Analysis of variance (ANOVA) was executed for checking the adequacy of the empirical models developed. It was discovered that the COF and wear-rate of composite MoS2-TiO2-ZrO2 coating significantly affected by the wt% addition of ZrO2. The SEM and optical microscopy analyses of the worn surfaces and transfer films indicated that the tribological properties of composite MoS2-TiO2-ZrO2 coating were significantly improved compared to pure MoS2 coating.
A MICROSTRUCTURE-BASED MECHANISTIC MODEL FOR BONE SAWING: PART 2 - ACOUSTIC ENERGY RATE PREDICTIONS
Authors: Mishra Roshan , Conward Michael , Samuel Johnson 
Published: May 2021

Abstract
Part-2 of this paper is focused on modeling the acoustic emission (AE) energy rate as a function of the specific cortical bone microstructures (viz., osteon, interstitial matrix, lamellar bone, and woven bone) and the depth-of-cut encountered by the bone sawtooth. First, the AE signal characteristics from the sawing experiments (in Part-1) are related to the pure haversian and pure plexiform regions of the cut. Using the cutting force predictions from Part-1 as input, the AE energy rate is then modeled in terms of the energies dissipated in the shearing and ploughing zones encountered by the rounded cutting edge. For this calculation, the rounded edge geometry of the sawtooth is modeled as a combination of (i) shear-based cutting from a negative rake cutting tool; and (ii) ploughing deformation from a round-nose indenter. The spread seen in the AE energy rate is captured by modeling the variations in sawed surface height profile, tool cutting edge geometry, and porosity of the bone. The model calibration and validation protocols are similar to those used in Part-1. The validated AE model is useful for process planning both in terms of its ability to predict AE energy rate trends and cutting force variations, based on the differences in the underlying bone microstructures.
A new K-Ar illite dating application to constrain the timing of subduction in West Sarawak, Borneo
Authors: Zhao Qi , Yan Yi , Tonai Satoshi , Tomioka Naotaka , Clift Peter D. , Hassan Meor H. Amir , Aziz Jasmi Hafiz Bin Abdul 
Published: May 2021

Abstract
The timing of subduction is a fundamental tectonic problem for tectonic models, yet there are few direct geological proxies for constraining it. However, the matrix of a tectonic mélange formed in a subduction-accretion setting archives the physical/chemical attributes at the time of deformation during the subduction-accretion process. Thus, the deformation age of the matrix offers the possibility to directly constrain the period of the subduction-accretion process. Here we date the Lubok Antu tectonic mélange and the overlying Lupar Formation in West Sarawak, Borneo by K-Ar analysis of illite. The ages of authigenic illite cluster around 60 Ma and 36 Ma. The maximum temperatures calculated by vitrinite reflectance values suggest that our dating results were not affected by external heating. Thus, the ages of authigenic illite represent the deformation age of the mélange matrix and the timing of the Rajang Unconformity, indicating that the subduction in Sarawak could have continued until ca. 60 Ma and the thermal and/or fluid flow events triggered by a major uplift of the Rajang Group occurred at ca. 36 Ma. Furthermore, this study highlights the potential of using the tectonic mélange to extract the timeframe of subduction zone episodic evolution directly.
Direct measurement of fungal contribution to silicate weathering rates in soil
Authors: Wild Bastien , Imfeld Gwenaël , Daval Damien 
Published: May 2021

AbstractChemical weathering produces solutes that control groundwater chemistry and supply ecosystems with essential nutrients. Although microbial activity influences silicate weathering rates and associated nutrient fluxes, its relative contribution to silicate weathering in natural settings remains largely unknown. We provide the first quantitative estimates of in situ silicate weathering rates that account for microbially induced dissolution and identify microbial actors associated with weathering. Nanoscale topography measurements showed that fungi colonizing olivine [(Mg,Fe)2SiO4] samples in a Mg-deficient forest soil accounted for up to 16% of the weathering flux after 9 mo of incubation. A local increase in olivine weathering rate was measured and attributed to fungal hyphae of Verticillium sp. Altogether, this approach provides quantitative parameters of bioweathering (i.e., rates and actors) and opens new avenues to improve elemental budgets in natural settings.
Mass balance controls on sediment scour and bedrock erosion in waterfall plunge pools
Authors: Scheingross Joel S. , Lamb Michael P. 
Published: May 2021

AbstractWaterfall plunge pools experience cycles of sediment aggradation and scour that modulate bedrock erosion, habitat availability, and hazard potential. We calculate sediment flux divergence to evaluate the conditions under which pools deposit and scour sediment by comparing the sediment transport capacities of waterfall plunge pools (Qsc_pool) and their adjacent river reaches (Qsc_river). Results show that pools fill with sediment at low river discharge because the waterfall jet is not strong enough to transport the supplied sediment load out of the pool. As discharge increases, the waterfall jet strengthens, allowing pools to transport sediment at greater rates than in adjacent river reaches. This causes sediment scour from pools and bar building at the downstream pool boundary. While pools may be partially emptied of sediment at modest discharge, floods with recurrence intervals &gt;10 yr are typically required for pools to scour to bedrock. These results allow new constraints on paleodischarge estimates made from sediment deposited in plunge pool bars and suggest that bedrock erosion at waterfalls with plunge pools occurs during larger floods than in river reaches lacking waterfalls.
Measuring change at Earth’s surface: On-demand vertical and three-dimensional topographic differencing implemented in OpenTopography
Authors: Scott Chelsea , Phan Minh , Nandigam Viswanath , Crosby Christopher , Arrowsmith J Ramon 
Published: May 2021

AbstractTopographic differencing measures landscape change by comparing multitemporal high-resolution topography data sets. Here, we focused on two types of topographic differencing: (1) Vertical differencing is the subtraction of digital elevation models (DEMs) that span an event of interest. (2) Three-dimensional (3-D) differencing measures surface change by registering point clouds with a rigid deformation. We recently released topographic differencing in OpenTopography where users perform on-demand vertical and 3-D differencing via an online interface. OpenTopography is a U.S. National Science Foundation–funded facility that provides access to topographic data and processing tools. While topographic differencing has been applied in numerous research studies, the lack of standardization, particularly of 3-D differencing, requires the customization of processing for individual data sets and hinders the community’s ability to efficiently perform differencing on the growing archive of topography data. Our paper focuses on streamlined techniques with which to efficiently difference data sets with varying spatial resolution and sensor type (i.e., optical vs. light detection and ranging [lidar]) and over variable landscapes. To optimize on-demand differencing, we considered algorithm choice and displacement resolution. The optimal resolution is controlled by point density, landscape characteristics (e.g., leaf-on vs. leaf-off), and data set quality. We provide processing options derived from metadata that allow users to produce optimal high-quality results, while experienced users can fine tune the parameters to suit their needs. We anticipate that the differencing tool will expand access to this state-of-the-art technology, will be a valuable educational tool, and will serve as a template for differencing the growing number of multitemporal topography data sets.
Intra-oceanic submarine arc evolution recorded in an ~1-km-thick rear-arc succession of distal volcaniclastic lobe deposits
Authors: Johnson Kyle , Marsaglia Kathleen M. , Brandl Philipp A. , Barth Andrew P. , Waldman Ryan , Ishizuka Osamu , Hamada Morihisa , Gurnis Michael , Ruttenberg Ian 
Published: May 2021

Abstract
International Ocean Discovery Program (IODP) Expedition 351 drilled a rear-arc sedimentary succession ~50 km west of the Kyushu-Palau Ridge, an arc remnant formed by rifting during formation of the Shikoku Basin and the Izu-Bonin-Mariana arc. The ~1-km-thick Eocene to Oligocene deep-marine volcaniclastic succession recovered at Site U1438 provides a unique opportunity to study a nearly complete record of intra-oceanic arc development, from a rear-arc perspective on crust created during subduction initiation rather than supra-subduction seafloor spreading. Detailed facies analysis and definition of depositional units allow for broader stratigraphic analysis and definition of lobe elements. Patterns in gravity-flow deposit types and subunits appear to define a series of stacked lobe systems that accumulated in a rear-arc basin. The lobe subdivisions, in many cases, are a combination of a turbidite-dominated subunit and an overlying debris-flow subunit. Debris flow–rich lobe-channel sequences are grouped into four, 1.6–2 m.y. episodes, each roughly the age range of an arc volcano. Three of the episodes contain overlapping lobe facies that may have resulted from minor channel switching or input from a different source. The progressive up-section coarsening of episodes and the increasing channel-facies thicknesses within each episode suggest progressively prograding facies from a maturing magmatic arc. Submarine geomorphology of the modern Mariana arc and West Mariana Ridge provide present-day examples that can be used to interpret the morphology and evolution of the channel (or channels) that fed sediment to Site U1438, forming the sequences interpreted as depositional lobes. The abrupt change from very thick and massive debris flows to fine-grained turbidites at the unit III to unit II boundary reflects arc rifting and progressive waning of turbidity current and ash inputs. This interpretation is consistent with the geochemical record from melt inclusions and detrital zircons. Thus, Site U1438 provides a unique record of the life span of an intra-oceanic arc, from inception through maturation to its demise by intra-arc rifting and stranding of the remnant arc ridge.
Coseismic deformation of the ground during large-slip strike-slip ruptures: Finite evolution of “mole tracks”
Authors: Little T.A. , Morris P. , Hill M.P. , Kearse J. , Van Dissen R.J. , Manousakis J. , Zekkos D. , Howell A. 
Published: May 2021

Abstract
To evaluate ground deformation resulting from large (~10 m) coseismic strike-slip displacements, we focus on deformation of the Kekerengu fault during the November 2016 Mw 7.8 Kaikōura earthquake in New Zealand. Combining post-earthquake field observations with analysis of high-resolution aerial photography and topographic models, we describe the structural geology and geomorphology of the rupture zone. During the earthquake, fissured pressure bulges (“mole tracks”) initiated at stepovers between synthetic Riedel (R) faults. As slip accumulated, near-surface “rafts” of cohesive clay-rich sediment, bounded by R faults and capped by grassy turf, rotated about a vertical axis and were internally shortened, thus amplifying the bulges. The bulges are flanked by low-angle contractional faults that emplace the shortened mass of detached sediment outward over less-deformed ground. As slip accrued, turf rafts fragmented into blocks bounded by short secondary fractures striking at a high angle to the main fault trace that we interpret to have originated as antithetic Riedel (R′) faults. Eventually these blocks were dispersed into strongly sheared earth and variably rotated. Along the fault, clockwise rotation of these turf rafts within the rupture zone averaged ~20°–30°, accommodating a finite shear strain of 1.0–1.5 and a distributed strike slip of ~3–4 m. On strike-slip parts of the fault, internal shortening of the rafts averaged 1–2 m parallel to the R faults and ~1 m perpendicular to the main fault trace. Driven by distortional rotation, this contraction of the rafts exceeds the magnitude of fault heave. Turf rafts on slightly transtensional segments of the fault were also bulged and shortened—relationships that can be explained by a kinematic model involving “deformable slats.” In a paleoseismic trench cut perpendicular the fault, one would observe fissures, low-angle thrusts, and steeply dipping strike-slip faults—some cross-cutting one another—yet all may have formed during a single earthquake featuring a large strike-slip displacement.
Joint association between accelerometry-measured daily combination of time spent in physical activity, sedentary behaviour and sleep and all-cause mortality: a pooled analysis of six prospective cohorts using compositional analysis
Authors: Chastin Sebastien , McGregor Duncan , Palarea-Albaladejo Javier , Diaz Keith M , Hagströmer Maria , Hallal Pedro Curi , van Hees Vincent T , Hooker Steven , Howard Virginia J , Lee I-Min , von Rosen Philip , Sabia Séverine , Shiroma Eric J , Yerramalla Manasa S , Dall Philippa 
Published: May 2021

ObjectiveTo examine the joint associations of daily time spent in different intensities of physical activity, sedentary behaviour and sleep with all-cause mortality.MethodsFederated pooled analysis of six prospective cohorts with device-measured time spent in different intensities of physical activity, sedentary behaviour and sleep following a standardised compositional Cox regression analysis.Participants130 239 people from general population samples of adults (average age 54 years) from the UK, USA and Sweden.Main outcomeAll-cause mortality (follow-up 4.3–14.5 years).ResultsStudies using wrist and hip accelerometer provided statistically different results (I2=92.2%, Q-test p<0.001). There was no association between duration of sleep and all-cause mortality, HR=0.96 (95% CI 0.67 to 1.12). The proportion of time spent in moderate to vigorous physical activity was significantly associated with lower risk of all-cause mortality (HR=0.63 (95% CI 0.55 to 0.71) wrist; HR=0.93 (95% CI 0.87 to 0.98) hip). A significant association for the ratio of time spent in light physical activity and sedentary time was only found in hip accelerometer-based studies (HR=0.5, 95% CI 0.42 to 0.62). In studies based on hip accelerometer, the association between moderate to vigorous physical activity and mortality was modified by the balance of time spent in light physical activity and sedentary time.ConclusionThis federated analysis shows a joint dose–response association between the daily balance of time spent in physical activity of different intensities and sedentary behaviour with all-cause mortality, while sleep duration does not appear to be significant. The strongest association is with time spent in moderate to vigorous physical activity, but it is modified by the balance of time spent in light physical activity relative to sedentary behaviour.