scholarly journals Cosmological Constant Dominated Transit Universe from the Early Deceleration Phase to the Current Acceleration Phase in Bianchi-V Spacetime

2012 ◽  
Vol 29 (7) ◽  
pp. 079801 ◽  
Author(s):  
Anil Kumar Yadav
Keyword(s):  
Cosmological Constant ◽  
Acceleration Phase ◽  
Deceleration Phase ◽  
Bianchi V ◽  
Transit Universe

scholarly journals A Wind-Storage Combined Frequency Regulation Control Strategy Based on Improved Torque Limit Control

2021 ◽  
Vol 13 (7) ◽  
pp. 3765
Author(s):  
Benxi Hu ◽  
Fei Tang ◽  
Dichen Liu ◽  
Yu Li ◽  
Xiaoqing Wei
Keyword(s):  
Control Strategy ◽  
Storage System ◽  
Energy Storage System ◽  
Frequency Regulation ◽  
Small Scale ◽  
Acceleration Phase ◽  
Deceleration Phase ◽  
Combined Control ◽  
Inertial Response ◽  
Battery Energy

The doubly-fed induction generator (DFIG) uses the rotor’s kinetic energy to provide inertial response for the power system. On this basis, this paper proposes an improved torque limit control (ITLC) strategy for the purpose of exploiting the potential of DFIGs’ inertial response. It includes the deceleration phase and acceleration phase. To shorten the recovery time of the rotor speed and avoid the second frequency drop (SFD), a small-scale battery energy storage system (BESS) is utilized by the wind-storage combined control strategy. During the acceleration phase of DFIG, the BESS adaptively adjusts its output according to its state of charge (SOC) and the real-time output of the DFIG. The simulation results prove that the system frequency response can be significantly improved through ITLC and the wind-storage combined control under different wind speeds and different wind power penetration rates.

scholarly journals A conceptual model of cyclical glacier flow in overdeepenings

2014 ◽  
Vol 8 (4) ◽  
pp. 4463-4495 ◽  
Author(s):  
J. B. Turrin ◽  
R. R. Forster
Keyword(s):  
Conceptual Model ◽  
The Other ◽  
Acceleration Phase ◽  
Alaska Range ◽  
Deceleration Phase ◽  
Surface Slopes ◽  
Glacier Dynamics ◽  
Major Tributary ◽  
Cyclical Behavior ◽  
Glacier Flow

Abstract. A nearly four-decade, satellite-based velocity survey of the largest glaciers in the Alaska Range, Chugach Mountains, and the Wrangell Mountains of southern Alaska, spanning the early- to mid-1970s through the 2000s, reveals nine pulsing glaciers: Capps, Copper, Eldridge, Kahiltna, Matanuska, Nabesna, Nizina, Ruth, and Sanford glaciers. The pulses increase velocity by up to 2449% (Capps Glacier) or as little as 77% (Nabesna Glacier), with velocity increases for the other glaciers in the range of 100–250%. The pulses may last from between six years (Copper Glacier) to 12 years (Nizina Glacier) and consist of a multi-year acceleration phase followed by a multi-year deceleration phase during which significant portions of each glacier move en masse. The segments of each glacier affected by the pulses may be anywhere from 14 km (Sanford Glacier) to 36 km (Nabesna Glacier) in length and occur where the glaciers are either laterally constricted or joined by a major tributary, and the surface slopes at these locations are very shallow, 1–2°, suggesting the pulses occur where the glaciers are overdeepened. A conceptual model to explain the cyclical behavior of these pulsing glaciers is presented that incorporates the effects of glaciohydraulic supercooling, glacier dynamics, surface ablation, and subglacial sediment erosion, deposition, and deformation in overdeepenings.

Analysis of ABS Plastic and Concentric Cylindrical Shells’ Chemical Detonation Scatter Process

2014 ◽  
Vol 574 ◽  
pp. 421-424
Author(s):  
Yue Guo Shen ◽  
Nai Juan Du ◽  
Jun Hai Zhang
Keyword(s):  
Mathematical Model ◽  
Water Molecules ◽  
Initial Moment ◽  
Acceleration Phase ◽  
Phase Form ◽  
Scatter Process ◽  
Deceleration Phase ◽  
Liquid Ring ◽  
Scatter Experiment ◽  
Phase Motion

In this paper, basing on the FAE theory, simulating the process of scatter from chemical detonation about ABS plastic and concentric cylindrical shell according to experiment, on the basis of the assumption that the initial moment of the explosion being at the source ,we analyzed the gaseous phase motion equation and liquid ring controlling equation, and build the liquid ring movement mathematical model, then analyze the scatter process according to the chemical detonation scatter experiment, and classify the chemical detonation scatter into acceleration phase and deceleration phase, form the initial fog group, then we can reveal the mechanism of changing the chemical detonation into the fog. After the initial fog being formed, the effect of the chemical detonation disappeared, and the water molecules are uniformly dispersed into the air.

Factors Affecting Navigation of the S.S.T.

1965 ◽  
Vol 18 (4) ◽  
pp. 498-504 ◽  
Author(s):  
B.O.A.C
Keyword(s):  
Noise Reduction ◽  
Vertical Plane ◽  
Acceleration Phase ◽  
Factors Affecting ◽  
Deceleration Phase ◽  
Aircraft Navigation ◽  
Special Factors ◽  
Performance Variations ◽  
Subsonic Region ◽  
Made In

This note provides some qualitative impressions of the need for precise navigation in the S.S.T. operation having due regard to performance and noise. It highlights the increased signific ance of the vertical plane, but quantitative conclusions as to horizontal ability cannot be made in the absence of knowledge of traffic amounts. It suggests that any tactical ‘chasing’ of noise reduction through performance variations not planned before flight is impracticable.In common with other aircraft types, the S.S.T. has three distinct phases of flight apart from take-off and landing: climb to cruise altitude, cruise and descent. The S.S.T. climb is characterized by an acceleration phase dividing the subsonic portion of flight from the supersonic. Similarly, the descent profile includes a deceleration phase which restores flight to the subsonic region. Contained in these three phases of flight unique to the S.S.T.—acceleration, supersonic flight and deceleration—are some of the special factors affecting aircraft navigation.

scholarly journals Are reaching and grasping effector-independent? Similarities and differences in reaching and grasping kinematics between the hand and foot

2021 ◽  
Author(s):  
Yuqi Liu ◽  
James Caracoglia ◽  
Sriparna Sen ◽  
Ella Striem-Amit
Keyword(s):  
Peak Velocity ◽  
Object Size ◽  
Body Parts ◽  
Acceleration Phase ◽  
Grip Aperture ◽  
Deceleration Phase ◽  
Neural Representations ◽  
Maximum Grip Aperture ◽  
Similarities And Differences ◽  
Maximum Grip

While reaching and grasping are highly prevalent manual actions, neuroimaging studies provide evidence that their neural representations may be shared between different body parts, i.e. effectors. If these actions are guided by effector-independent mechanisms, similar kinematics should be observed when the action is performed by the hand or by a cortically remote and less experienced effector, such as the foot. We tested this hypothesis with two characteristic components of action: the initial ballistic stage of reaching, and the preshaping of the digits during grasping based on object size. We examined if these kinematic features reflect effector-independent mechanisms by asking participants to reach toward and to grasp objects of different widths with their hand and foot. First, during both reaching and grasping, the velocity profile up to peak velocity matched between the hand and the foot, indicating a shared ballistic acceleration phase. Secondly, maximum grip aperture and time of maximum grip aperture of grasping increased with object size for both effectors, indicating encoding of object size during transport. Differences between the hand and foot were found in the deceleration phase and time of maximum grip aperture, likely due to biomechanical differences and the participants' inexperience with foot actions. These findings provide evidence for effector-independent visuomotor mechanisms of reaching and grasping that generalize across body parts.

scholarly journals DECELERATION PHASE MOMENTS: A POTENTIAL CAUSE FOR ELBOW INJURY IN COLLEGIATE LEVEL BASEBALL PITCHERS

2019 ◽  
Vol 7 (3_suppl) ◽  
pp. 2325967119S0007
Author(s):  
Matthew J. Solomito ◽  
Erin J. Garibay ◽  
Carl W. Nissen
Keyword(s):  
Elbow Joint ◽  
Glenohumeral Joint ◽  
Skeletal Maturity ◽  
Maximum Height ◽  
Peak Acceleration ◽  
Acceleration Phase ◽  
Elbow Injury ◽  
Deceleration Phase ◽  
Significant Difference ◽  
Baseball Pitchers

Background: Over the past three decades there has been an increase in the incidence of elbow and shoulder pain experienced by baseball pitchers, which can limit or lead to an end of pitching activities. Although there are a number of theories that suggest poor pitching mechanics or throwing breaking pitches prior to skeletal maturity may be the cause, biomechanical investigations have yet to elucidate a single cause for this rise in injuries. It is also well established that the highest stresses and fastest angular velocities experienced by pitchers occurs during the acceleration phase of the pitch cycle, which has led to extensive biomechanical investigations of this portion of the pitching cycle. However, the deceleration phase of the pitch, although 150% longer than the acceleration phase, still requires an abrupt reversal of motion to allow pitchers to get into a fielding position after they have delivered the pitch. Therefore, the purpose of this study was to determine if the elbow joint was subjected to an additional varus stress during the deceleration phase of the pitch cycle. Methods: NCAA Division I and Division III baseball pitchers were recruited for this study and underwent a comprehensive biomechanical pitching evaluation. All pitchers were injury free at the time of data collection and reported no history of an upper extremity injury within the previous six months of the analysis date. Additionally, all pitchers had at least two years of pitching experience. All participants pitched from a 10” mound towards a target with a designated strike zone set 60’6” away. Kinematic data was collected using a 12-camera motion capture system, and kinetic data was calculated using standard inverse dynamic techniques. The typical pitching cycle, starting with lead foot contact and ending with maximum internal rotation of the glenohumeral joint (MIR), was expanded to end when the pedestal foot reached its maximum height; allowing for the analysis of deceleration phase moments at the elbow joint. The deceleration phase elbow varus (EV) moment was compared across multiple pitch types (i.e. fastball, curveball, slider, and change-up) using the type III effects from a random intercept mixed effects model. Additionally, the deceleration phase EV moment was compared to the peak EV moment occurring during the acceleration phase of the pitch cycle. Results: The results of this study are based on 87 baseball pitchers with a mean age of 19.9 ± 1.4 years. All participants pitched a fastball, 78 pitched a curveball, 31 pitched a slider, and 60 pitched a change-up. The results indicated that there was the presence of an elbow varus moment for all pitch types that occurred during the deceleration phase of the pitching cycle after MIR that was on average about half of the peak acceleration phase moment (Table 1). Overall 26% of pitchers pitching a fastball, 33% of pitchers throwing a curveball and change-up, and 55% of pitchers throwing a slider had deceleration EV moments greater than 50% of their peak acceleration phase EV moment. There was a statistically significant difference in the number of pitchers with a deceleration phase EV moment greater than half of the acceleration phase EV moment when pitching the slider when compared to the other pitch types (p=0.029). Conclusion/Significance: The majority of pitching biomechanics research focuses on the acceleration phase of the pitching cycle because the highest speeds and moments are achieved during this portion of the pitch. However, the pitcher’s need to rapidly decelerate during the pitch does expose them to an additional elbow varus moment. This additional moment could be a potential source of injury as it is a second stress exposure for the UCL. Additionally, given that the highest deceleration EV moments were noted in the slider this may potentially explain why pitchers and coaches believe that sliders are more harmful than other pitch types. [Table: see text]

scholarly journals Using Kinetic Energy with Potential Energy When Determining Power During the Stair Climbing Test

2020 ◽  
Author(s):  
James Roush ◽  
John Heick ◽  
Joseph Genovese ◽  
Kyle Kurashima ◽  
Dallin Yarrington
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Stair Climbing ◽  
Total Power ◽  
Accurate Assessment ◽  
Acceleration Phase ◽  
Deceleration Phase ◽  
Vital Component ◽  
The Mean ◽  
Functional Task

ABSTRACT Stair climbing is an important functional task that indicates independence, and generating power to climb stairs is a vital component of this task. Power during stair climbing is traditionally calculated using potential energy (PE), but it may be important to determine power expended using kinetic energy (KE). Purpose: The current study assessed power output for stair climbing with and without the inclusion of KE. Methods: Sixty participants (21-35 years) climbed a 12-step stairway with a 2-meter acceleration phase before the first step and a 2-meter deceleration phase after the last step. Participants completed 3 trials, and average time was used for calculating energy expended and power. Results: The mean difference between power from PE and total power was 6.16 W (SD = 2.50, t29 = 13.49, p < 0.001) for males and 64.76 W (SD = 2.90, t29 = 8.99, p < 0.001) for females. Agreement between power calculated from PE and total power was 0.99 (95% confidence interval = 0.98-1.0). Conclusion: Power calculated using PE and KE was significantly different from using PE alone, which may be clinically important. When conducting stair-climbing tests, both PE and KE may be necessary for the most accurate assessment of power.

Representation of hand position prior to movement and motor variability

1995 ◽  
Vol 73 (2) ◽  
pp. 262-272 ◽  
Author(s):  
Michel Desmurget ◽  
Yves Rossetti ◽  
Claude Prablanc ◽  
Marc Jeannerod ◽  
George E. Stelmach
Keyword(s):  
Peak Velocity ◽  
Human Subjects ◽  
Hand Position ◽  
Feedback Process ◽  
Significant Modification ◽  
Movement Kinematics ◽  
Acceleration Phase ◽  
Movement Onset ◽  
Motor Variability ◽  
Deceleration Phase

Pointing accurary of six human subjects was measured in two blocked conditions where the hand was either never visible (T: target only) or only visible in static position prior to movement onset (H+T: hand + target). It was shown in condition H+T that, viewing the hand prior to movement greatly decreased end-point variability compared with condition T. This effect was associated with a significant modification of the movement kinematics: the H+T condition induced a shortened acceleration phase with a corresponding lengthened deceleration phase, compared with the T condition. These results led us to the hypothesis that viewing the hand prior to movement onset allowed a decrease of pointing variability through a feedback process. This hypothesis was further tested by turning the target off during the deceleration phase of the movement at half peak velocity. It was shown that turning the target off had no effect upon the T condition but induced a significant increase of pointing variability in the H+T condition. This result suggests that vision of the static hand enhances the proprioceptive localization of the limb and allows for a better visual to kinesthesic feedback.Key words: proprioception, vision, motor control, pointing, feedback, human.

scholarly journals DARKON FLUID — A MODEL FOR THE DARK SECTOR OF THE UNIVERSE?

2012 ◽  
Vol 09 (06) ◽  
pp. 1261014 ◽  
Author(s):  
P. C. STICHEL ◽  
WOJTEK J. ZAKRZEWSKI
Keyword(s):  
Early Universe ◽  
Mass Density ◽  
Gravitational Coupling ◽  
Dark Sector ◽  
Acceleration Phase ◽  
Confining Potential ◽  
Deceleration Phase ◽  
Anisotropic Scaling ◽  
Cosmological Solutions ◽  
The Universe

We introduce darkons as fluid particles of a Galilean massless self-gravitating fluid. This fluid exhibits anisotropic scaling with [Formula: see text]. The minimal gravitational coupling dynamically generates a gravitational mass density of either sign. Hence such fluid may serve as a model for the dark sector of the Universe. Its cosmological solutions give a deceleration phase for the early Universe and an acceleration phase for the late Universe. Will the steady flow solutions lead to a confining potential and so a possible model for halos?

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