Analysis of landing position of explosively formed projectile under the decoy jamming of terminal-sensitive projectile

Seven top amateur or professional skateboarders (BW = 713 N ± 83 N) performed Ollie maneuvers onto and off an elevated wooden platform (45.7 cm high). We recorded ground reaction force (GRF) data for three Ollie Up (OU) and Ollie Down (OD) trials per participant. The vertical GRF (VGRF) during the OU has a characteristic propulsive peak (M = 2.22 body weight [BW] ± 0.22) resulting from rapidly rotating the tail of the board into the ground to propel the skater and board up and forward. The anterior-posterior (A-P) GRF also shows a pronounced peak (M = 0.05 ± 0.01 BW) corresponding with this propulsive VGRF peak. The initial phase of landing in the OD shows an impact peak in VGRF rising during the first 30 to 80 ms to a mean of 4.74 ± 0.46 BW. These impact peaks are higher than expected given the relatively short drop of 45.7 cm and crouched body position. But we observed that our participants intentionally affected a firm landing to stabilize the landing position; and the Ollie off the platform raised the center of mass, also contributing to higher forces.

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Effects of reward on oculomotor control

Journal of Neurophysiology ◽

10.1152/jn.00498.2016 ◽

2016 ◽

Vol 116 (5) ◽

pp. 2453-2466 ◽

Cited By ~ 9

Author(s):

Brónagh McCoy ◽

Jan Theeuwes

Keyword(s):

Reward Magnitude ◽

Saccade Latency ◽

Oculomotor Control ◽

Distractor Location ◽

Landing Position ◽

Bayesian Hierarchical ◽

Visual Hemifield ◽

High Reward ◽

And Control ◽

Remote Distractor Effect

The present study examines the extent to which distractors that signal the availability of monetary reward on a given trial affect eye movements. We used a novel eye movement task in which observers had to follow a target around the screen while ignoring distractors presented at varying locations. We examined the effects of reward magnitude and distractor location on a host of oculomotor properties, including saccade latency, amplitude, landing position, curvature, and erroneous saccades toward the distractor. We found consistent effects of reward magnitude on classic oculomotor phenomena such as the remote distractor effect, the global effect, and oculomotor capture by the distractor. We also show that a distractor in the visual hemifield opposite to the target had a larger effect on oculomotor control than an equidistant distractor in the same hemifield as the target. Bayesian hierarchical drift diffusion modeling revealed large differences in drift rate depending on the reward value, location, and visual hemifield of the distractor stimulus. Our findings suggest that high reward distractors not only capture the eyes but also affect a multitude of oculomotor properties associated with oculomotor inhibition and control.

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A Numerical Model for Investigating the Steam Conformance along the Dual-String Horizontal Wells in SAGD Operations

Energies ◽

10.3390/en13153981 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3981

Author(s):

Peng Li ◽

Yanyu Zhang ◽

Xiaofei Sun ◽

Huijuan Chen ◽

Yang Liu

Keyword(s):

Pressure Drop ◽

Horizontal Wells ◽

Pressure Profile ◽

Steam Injection ◽

Steam Pressure ◽

Optimization Method ◽

Injection Time ◽

Reservoir Model ◽

Landing Position ◽

Steam Chamber

Non-uniformity of the steam-assisted gravity drainage (SAGD) steam chamber significantly decreases the development of heavy oil reservoirs. In this study, to investigate the steam conformance in SAGD operations, a wellbore model is developed for fluid flow in dual-string horizontal wells. Then, a three-dimensional, three-phase reservoir model is presented. Next, the coupled wellbore and reservoir model is solved with a fully implicit finite difference method. Finally, the effects of the injector wellbore configuration, steam injection ratio and injection time on the steam conformance are investigated. The results indicate that under different injector wellbore configurations, the closer the differences between the pressure drop from the landing position of the short string to the heel of the wellbore and the pressure drop from the landing position of the short string to the toe of the wellbore, the better is the steam conformance. The smaller the difference in the steam injection rate between the long and short injection strings, the higher is the uniformity of the steam chamber. The injector annular pressure profile uniformity is consistent with the steam conformance. Creating a more uniform steam pressure in the annulus of the injector improves the uniformity of the steam chamber. The steam conformance decreases with increasing injection time, so the optimization method of steam chamber uniformity should be adjusted according to different injection times.

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A Precise and GNSS-Free Landing System on Moving Platforms for Rotary-Wing UAVs

Sensors ◽

10.3390/s19040886 ◽

2019 ◽

Vol 19 (4) ◽

pp. 886 ◽

Cited By ~ 3

Author(s):

Francisco Alarcón ◽

Manuel García ◽

Ivan Maza ◽

Antidio Viguria ◽

Aníbal Ollero

Keyword(s):

Relative Position ◽

Unmanned Helicopter ◽

Landing Position ◽

Moving Platforms ◽

Landing Platform ◽

Aerial Vehicle ◽

The Stability ◽

Novel Concept ◽

High Level ◽

Rotary Wing

This article presents a precise landing system that allows rotary-wing UAVs to approach and land safely on moving platforms, without using GNSS at any stage of the landing maneuver, and with a centimeter level accuracy and high level of robustness. This system implements a novel concept where the relative position and velocity between the aerial vehicle and the landing platform are calculated from the angles of a cable that physically connects the UAV and the landing platform. The use of a cable also incorporates a number of extra benefits, such as increasing the precision in the control of the UAV altitude. It also facilitates centering the UAV right on top of the expected landing position, and increases the stability of the UAV just after contacting the landing platform. The system was implemented in an unmanned helicopter and many tests were carried out under different conditions for measuring the accuracy and the robustness of the proposed solution. Results show that the developed system allowed landing with centimeter accuracy by using only local sensors and that the helicopter could follow the landing platform in multiple trajectories at different velocities.

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Energy Absorption Strategies in the Lower Extremities during Double-Leg Landings in Knee Valgus Alignment

Applied Sciences ◽

10.3390/app10238742 ◽

2020 ◽

Vol 10 (23) ◽

pp. 8742

Author(s):

Akihiro Tamura ◽

Kiyokazu Akasaka ◽

Takahiro Otsudo

Keyword(s):

Energy Absorption ◽

Mechanical Load ◽

Three Dimensional ◽

Lower Extremities ◽

Mechanical Work ◽

Knee Valgus ◽

Landing Position ◽

Drop Jumps ◽

Analysis System ◽

Valgus Alignment

Landing with the knee in a valgus position may alter energy absorption strategies in the lower extremities and increase mechanical stress on the knee joint. We compared the energy absorption strategies in the lower extremities during valgus and varus landings. Seventeen females were divided into valgus and varus groups. Lower extremity kinetic data were obtained during drop jumps, using a three-dimensional motion analysis system. Negative mechanical work in the lower extremities were calculated during landing. The valgus group exhibited significantly more negative mechanical work at the knee, and less negative mechanical work at the hip, compared with the varus group. However, there was no difference in the negative mechanical work at the ankle between the two groups. Findings suggest that an increased valgus landing reduces the contribution of the hip to energy absorption and is associated with a reciprocal increased contribution by the knee. Hence a knee valgus landing position may be a key biomechanical factor that increases energy absorption in the knee, thereby increasing the risk of injury. Results further indicate that this can be prevented by adopting a knee varus position on landing, which facilitates absorption of the mechanical load at the hip, rather than at the knee.

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Saccadic Localisation of Random Dot Targets

Perception ◽

10.1068/v96l0304 ◽

1996 ◽

Vol 25 (1_suppl) ◽

pp. 101-101 ◽

Cited By ~ 1

Author(s):

J W McGowan ◽

E Kowler ◽

A Sharma ◽

C Chubb

Keyword(s):

Saccadic Eye Movements ◽

Natural Scenes ◽

Landing Position ◽

Local Pattern ◽

Centre Of Gravity ◽

Local Characteristics ◽

Spatial Pooling ◽

Initial Fixation ◽

Single Target ◽

Differential Weighting

Saccadic eye movements land at precise places within simple target forms implying that a spatial pooling process operates over attended regions to determine the saccadic endpoint. To study pooling, we used large, unstructured targets and looked for evidence of differential spatial weighting based on local pattern characteristics. Subjects made a saccade to targets composed of 19 dots scattered randomly within a 4 deg diameter region horizontally displaced 3.8 – 4.2 deg to the left or right of initial fixation. Dot intensity was either uniform or variable. Saccadic landing positions were close to the centre-of-gravity (overshooting or under- shooting by 5% – 10% depending on subject, direction and eccentricity). Precision was excellent (SD=10% ecc), although not as good as with single target points (SD=7% ecc). Correlations between the presence of a dot and saccadic landing position showed that all regions of the pattern contributed. Differential weighting of dots according to location (eg near vs far; central vs boundary) did not yield better predictions of the saccadic landing position. However, predictions of the landing position were improved by assigning more weight to higher-intensity dots. Local dot clusters contributed less than would be expected from the contributions of individual dots. Spatial pooling is highly effective over a large region. Saccadic overshoots or undershoots were not due to differential spatial weighting, and may originate after the centre-of-gravity computation. The differential weighting of high-intensity dots and dot clusters demonstrates sensitivity to local characteristics, and implies that the saccadic endpoint may be determined by pooling the activity of units centred on different subregions of the target. The pooling mechanism supports precise saccadic localisation of large, unstructured targets, and accounts for the ease with which we direct saccades to chosen objects in natural scenes.

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