scholarly journals Erratum to : A Note of Poynting Flow of Power of Sketch Mapping for a YAGI-UDA Antenna Above a Flat Ground

1996 ◽  
Vol 50 (7) ◽  
pp. e1-e1
Keyword(s):  
Flat Ground

scholarly journals Barrier-Free Wheelchair with a Mechanical Transmission

2021 ◽  
Vol 11 (11) ◽  
pp. 5280
Author(s):  
Jongseok Lee ◽  
Wonhyeong Jeong ◽  
Jaeoh Han ◽  
Taesu Kim ◽  
Sehoon Oh
Keyword(s):  
The Elderly ◽  
Transmission System ◽  
Motor Drives ◽  
Mechanical Transmission ◽  
Link Structure ◽  
Second Mode ◽  
Important Means ◽  
The Stability ◽  
Flat Ground ◽  
Climbing Stairs

Wheelchairs are an important means of transportation for the elderly and disabled. However, the movement of wheelchairs on long curbs and stairs is restricted. In this study, a wheelchair for climbing stairs was developed based on a mechanical transmission system that rotates the entire driving part through a link structure and an actuator to change the speed. The first mode drives the caterpillar, and the second mode drives the wheels. When driving on flat ground, it uses landing gears and wheels, and when climbing stairs, it uses the caterpillar; accordingly, a stable driving is possible. The stability of the transmission is confirmed through stress analysis. The method used in our study makes it is possible to manufacture lightweight wheelchairs because a single motor drives both the wheel and caterpillar through the transmission system.

Numerical Simulation of Radon Atmospheric Dynamic Diffusion from a Flat Ground Uranium Tailings Impoundment

2013 ◽  
Vol 807-809 ◽  
pp. 628-631
Author(s):  
Xiao Yong Peng ◽  
Xin Zhang ◽  
Shuai Huang ◽  
Xu Sheng Chai ◽  
Lan Xia Guo
Keyword(s):  
Numerical Simulation ◽  
Mass Fraction ◽  
Space Distribution ◽  
Time And Space ◽  
Tailings Impoundment ◽  
Diffusion Characteristics ◽  
Atmospheric Dynamic ◽  
Uranium Tailings ◽  
Dynamic Diffusion ◽  
Flat Ground

with a flat ground uranium tailings impoundment as the object of the paper, CFD technology was used to study the atmospheric dynamic diffusion characteristics and the evolution of time and space distribution of radon in the uranium tailings impoundment. Results show that, within 1500m range of the leeward of uranium tailings impoundment the falling gradient of radon mass fraction improves with distance increases at the same moment, however the falling gradient flattens with the increase of time gradually; During the first 30 minutes, the radon mass fraction of tailings impoundment in the leeward direction has a larger growth gradient, then flattens out slowly, and stabilizes after 75 minutes.

Navigation strategy for a quadruped robot on soft flat ground

ICCAS 2010 ◽  
2010 ◽  
Author(s):  
Masaaki Ikeda ◽  
Kiyotaka Izumi ◽  
Keigo Watanabe
Keyword(s):  
Quadruped Robot ◽  
Navigation Strategy ◽  
Flat Ground

scholarly journals Flat Ground Throwing Results in Decreased Ball Velocity and Increased Elbow Torque Compared to Mound Throwing

2019 ◽  
Vol 7 (7_suppl5) ◽  
pp. 2325967119S0036
Author(s):  
Daphne Ling ◽  
Christopher L. Camp ◽  
Brittany Dowling ◽  
Kathryn Mcelheny ◽  
Joshua S. Dines
Keyword(s):  
Good Reliability ◽  
Baseball Players ◽  
Linear Mixed Effects ◽  
Youth Baseball ◽  
Subject Variability ◽  
Ball Velocity ◽  
Surrogate Measure ◽  
Ground Distance ◽  
Evidenced Based ◽  
Flat Ground

Objectives: The incidence of shoulder and elbow overuse injury continues to rise in youth baseball players. Several throwing programs designed to reduce stress on the elbow have been described, but most are not evidence-based. The aim of this study was to compare the kinetics and kinematics between mound and flat-ground pitching at two different distances with the goal of developing evidenced-based injury prevention and recovery guidelines for youth throwers. Methods: Fifteen healthy, high school varsity-level baseball pitchers (mean age 16.7 ± 0.7 yrs; height 182.2 ± 6.2 cm; weight 76.0 ± 9.4 kg;) participated in the study. Players were fitted with a motusBASEBALLTM sensor and sleeve (Motus Global, Rockville Centre, NY), which has been shown to have good reliability and correlation with in-laboratory measures. Each pitcher was asked to pitch 5 fastballs to a catcher under each of the 4 conditions: mound at 60.5 ft (regulation distance), flat ground at 60.5 ft, mound at 50.5 ft, and flat ground at 50.5 ft. For each pitch, the sensor recorded arm speed, arm slot, shoulder rotation, and elbow varus torque. Ball velocity was tracked with a radar gun (Stalker Radar, Richardson, TX). Linear mixed-effects models were used to account for both within and between-subject variability. A multivariable model was used to evaluate the association of mound pitching (vs flat ground), distance (50.5 vs 60.5 ft), and their interaction on each of the following outcomes: arm speed, arm slot, shoulder rotation, elbow varus torque, and ball velocity. Results: There were no statistically significant effects of mound vs flat ground or distance variation on both arm speed or shoulder rotation. Arm slot was significantly higher on pitches from the mound at 60.5 ft [+4.58 (95% CI: 1.26, 7.90), p=0.007]. Elbow varus torque was significantly lower on throws from the mound [-1.88 (95% CI: -3.56, -0.20), p=0.03] and from a longer distance [-2.21 (95% CI: -3.89, -0.53), p=0.01]. Pitches thrown from the mound were significantly faster compared to flat ground at both distances, with throws at 60.5 ft of greater velocity than at 50.5 ft [+1.03 (95% CI: 0.66, 1.40), p<0.001]. Please see the Table for full results. Conclusion: The findings suggest that throwing from the mound may not be higher risk compared to flat ground, contrary to long-standing notions. The lower elbow varus torque and higher arm slot, which has previously been shown to be associated with reduced stress, from throwing from the mound may even indicate a protective effect. Compared to 50.5 ft, there was lower elbow varus torque and faster ball velocity at the longer distance, indicating that elbow stress and ball velocity may not correlate perfectly, and radar guns may not be an appropriate surrogate measure of elbow varus torque. A better understanding of the kinetic and kinematic implications of various throwing programs will allow for designing programs that are based on objective data to achieve the goal of preventing injuries in young baseball players. [Table: see text]

Adaptive tensegrity locomotion: Controlling a compliant icosahedron with symmetry-reduced reinforcement learning

2019 ◽  
pp. 027836491985944 ◽  
Author(s):  
David Surovik ◽  
Kun Wang ◽  
Massimo Vespignani ◽  
Jonathan Bruce ◽  
Kostas E Bekris
Keyword(s):  
Reinforcement Learning ◽  
Policy Design ◽  
Model Parameters ◽  
Locomotion Control ◽  
Small Variety ◽  
Sample Data ◽  
Hybrid Framework ◽  
Varying Environments ◽  
High Degree ◽  
Flat Ground

Tensegrity robots, which are prototypical examples of hybrid soft–rigid robots, exhibit dynamical properties that provide ruggedness and adaptability. They also bring about, however, major challenges for locomotion control. Owing to high dimensionality and the complex evolution of contact states, data-driven approaches are appropriate for producing viable feedback policies for tensegrities. Guided policy search (GPS), a sample-efficient hybrid framework for optimization and reinforcement learning, has previously been applied to generate periodic, axis-constrained locomotion by an icosahedral tensegrity on flat ground. Varying environments and tasks, however, create a need for more adaptive and general locomotion control that actively utilizes an expanded space of robot states. This implies significantly higher needs in terms of sample data and setup effort. This work mitigates such requirements by proposing a new GPS -based reinforcement learning pipeline, which exploits the vehicle’s high degree of symmetry and appropriately learns contextual behaviors that are sustainable without periodicity. Newly achieved capabilities include axially unconstrained rolling, rough terrain traversal, and rough incline ascent. These tasks are evaluated for a small variety of key model parameters in simulation and tested on the NASA hardware prototype, SUPERball. Results confirm the utility of symmetry exploitation and the adaptability of the vehicle. They also shed light on numerous strengths and limitations of the GPS framework for policy design and transfer to real hybrid soft–rigid robots.

Sutton Hoo Excavations, 1965–7

Antiquity ◽  
1968 ◽  
Vol 42 (165) ◽  
pp. 36-39
Author(s):  
R. L. S. Bruce-Mitford
Keyword(s):  
Bronze Age ◽  
Surface Features ◽  
Original Shape ◽  
Flat Ground

The first aim of this new excavation was to complete the study of the largest of the mounds. It was not known what the original shape of the mound was, whether oval or circular, what its height had been before excavation, whether it was surrounded by a ditch, or what structural or ritual features it might possess. It was also an aim to obtain more information about the site in general by cutting away the grass and bracken and making a fresh and sensitive survey of the surface features. In the process the number of barrows recognizable rose from 11 to 16. It was also an aim to sound the flat ground between and near the barrows to see whether ordinary burials, whether cremation or inhumation, could be located, and to establish the nature of the Neolithic-Bronze Age occupation plentifully attested on the site by stray finds.

Productivity of crops grown on raised beds on duplex soils prone to waterlogging in Western Australia

2007 ◽  
Vol 47 (11) ◽  
pp. 1368 ◽  
Author(s):  
D. M. Bakker ◽  
G. J. Hamilton ◽  
D. J. Houlbrooke ◽  
C. Spann ◽  
A. Van Burgel
Keyword(s):  
Grain Yield ◽  
Western Australia ◽  
Arable Land ◽  
Experimental Period ◽  
Grain Yields ◽  
Yield Increase ◽  
Field Peas ◽  
Yield Difference ◽  
Raised Bed ◽  
Flat Ground

Waterlogging of duplex soils in Western Australia has long been recognised as a major constraint to the production of agricultural crops and pastures. The work described in this paper examines the application of raised beds to arable land that is frequently waterlogged for the production of crops such as wheat, barley, field peas, lupins and canola. Raised beds are 138 cm wide, seed beds separated by 45 cm wide furrows 183 cm apart. These beds were made with a commercial bed former. Seven sites were selected across the south-eastern wheat belt of Western Australia with the experimental areas varying in size from 10 to 57 ha. These large sites were used to accommodate commercial farm machinery. Each site had raised beds formed with a commercial bedformer. The production from the bedded areas was compared with crops grown conventionally on flat ground under minimum tillage as the control. The experiments were established in 1997 and 1998 and the sites were monitored for a maximum of 5 years. In 11 of the 28 site-years of the experiments, grain yields on the raised beds were statistically significantly higher than the yield from crops grown on the control, with an average yield increase of 0.48 t/ha. Across the whole dataset, growing crops on raised beds did not produce significantly lower yields. Below average rainfall was received for much of the experimental period at several sites. Growing season rainfall had a large effect on grain yield and high rainfall over a period of 40 days after seeding significantly increased the grain yield difference between the raised bed and the control. These data indicate that the use of raised beds lead to higher grain yields when seasonal conditions are appropriate.

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