scholarly journals Differential contributions of fatigue‐induced strength loss and slowing of angular velocity to power loss following repeated maximal shortening contractions

2020 ◽  
Vol 8 (3) ◽  
Author(s):  
Ryota Akagi ◽  
Avery Hinks ◽  
Brooke Davidson ◽  
Geoffrey A. Power
Keyword(s):  
Angular Velocity ◽  
Power Loss ◽  
Strength Loss ◽  
Shortening Contractions

Postactivation potentiation in a human muscle: effect on the load-velocity relation of tetanic and voluntary shortening contractions

2007 ◽  
Vol 103 (4) ◽  
pp. 1318-1325 ◽  
Author(s):  
Stéphane Baudry ◽  
Jacques Duchateau
Keyword(s):  
Angular Velocity ◽  
Muscle Activation ◽  
Electrical Stimulus ◽  
Voluntary Contraction ◽  
Muscle Performance ◽  
Postactivation Potentiation ◽  
Muscle Twitch ◽  
Velocity Relation ◽  
Voluntary Contractions ◽  
Shortening Contractions

Recently it was demonstrated that postactivation potentiation (PAP), which refers to the enhancement of the muscle twitch torque as a result of a prior conditioning contraction, increased the maximal rate of torque development of tetanic and voluntary isometric contractions ( 3 ). In this study, we investigated the effects of PAP and its decay over time on the load-velocity relation. To that purpose, angular velocity of thumb adduction in response to a single electrical stimulus (twitch), a high-frequency train of 15 pulses at 250 Hz (HFT250), and during ballistic voluntary shortening contractions, performed against loads ranging from 10 to 50% of the maximum torque, were recorded before and after a conditioning 6-s maximal voluntary contraction (MVC). The results showed an increase of the peak angular velocity for the different loads tested after the conditioning MVC ( P < 0.001), but the effect was greatest for the twitch (∼182%) compared with the HFT250 or voluntary contractions (∼14% for both contraction types). The maximal potentiation occurred immediately following the conditioning MVC for the twitch, whereas it was reached 1 min later for the tetanic and ballistic voluntary contractions. At that time, the load-velocity relation was significantly shifted upward, and the maximal power of the muscle was increased (∼13%; P < 0.001). Furthermore, the results also indicated that the effect of PAP on shortening contractions was not related to the modality of muscle activation. In conclusion, the findings suggest a functional significance of PAP in human movements by improving muscle performance of voluntary dynamic contractions.

Zonal and tesseral harmonic perturbations of an artificial satellite

1966 ◽  
Vol 25 ◽  
pp. 323-325 ◽  
Author(s):  
B. Garfinkel
Keyword(s):  
Angular Velocity ◽  
Spherical Harmonics ◽  
Artificial Satellite ◽  
Compact Form ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Secular Variations ◽  
Tesseral Harmonics

The paper extends the known solution of the Main Problem to include the effects of the higher spherical harmonics of the geopotential. The von Zeipel method is used to calculate the secular variations of orderJmand the long-periodic variations of ordersJm/J2andnJm,λ/ω. HereJmandJm,λare the coefficients of the zonal and the tesseral harmonics respectively, withJm,0=Jm, andωis the angular velocity of the Earth's rotation. With the aid of the theory of spherical harmonics the results are expressed in a most compact form.

Structure characterization of ground calcium carbonate flocs by fractal analysis and their effects on handsheet properties

TAPPI Journal ◽  
2013 ◽  
Vol 12 (3) ◽  
pp. 17-23 ◽  
Author(s):  
WANHEE IM ◽  
HAK LAE LEE ◽  
HYE JUNG YOUN ◽  
DONGIL SEO
Keyword(s):  
Fractal Analysis ◽  
Structural Characteristics ◽  
Fractal Dimensions ◽  
Strength Loss ◽  
Structure Characterization ◽  
Uniform Size ◽  
Cross Sectional ◽  
Floc Size ◽  
Mass Fractal ◽  
Handsheet Properties

Preflocculation of filler particles before their addition to pulp stock provides the most viable and practical solution to increase filler content while minimizing strength loss. The characteristics of filler flocs, such as floc size and structure, have a strong influence on preflocculation efficiency. The influence of flocculant systems on the structural characteristics of filler flocs was examined using a mass fractal analysis method. Mass fractal dimensions of filler flocs under high shear conditions were obtained using light diffraction spectroscopy for three different flocculants. A single polymer (C-PAM), a dual cationic polymer (p-DADMAC/C-PAM) and a C-PAM/micropolymer system were used as flocculants, and their effects on handsheet properties were investigated. The C-PAM/micropolymer system gave the greatest improvement in tensile index. The mass fractal analysis showed that this can be attributed to the formation of highly dense and spherical flocs by this flocculant. A cross-sectional analysis of the handsheets showed that filler flocs with more uniform size were formed when a C-PAM/micropolymer was used. The results suggest that a better understanding of the characteristics of preflocculated fillers and their influence on the properties of paper can be gained based on a fractal analysis.

Upscaling of foam forming technology for pilot scale

TAPPI Journal ◽  
2019 ◽  
Vol 18 (8) ◽  
Author(s):  
JANI LEHMONEN ◽  
TIMO RANTANEN ◽  
KARITA KINNUNEN-RAUDASKOSKI
Keyword(s):  
Production Efficiency ◽  
Strength Loss ◽  
Pilot Scale ◽  
Foam Density ◽  
Forming Process ◽  
Production Scale ◽  
Forming Technology ◽  
Wet Pressing ◽  
Foam Forming ◽  
Board Industry

The need for production cost savings and changes in the global paper and board industry during recent years have been constants. Changes in the global paper and board industry during past years have increased the need for more cost-efficient processes and production technologies. It is known that in paper and board production, foam typically leads to problems in the process rather than improvements in production efficiency. Foam forming technology, where foam is used as a carrier phase and a flowing medium, exploits the properties of dispersive foam. In this study, the possibility of applying foam forming technology to paper applications was investigated using a pilot scale paper forming environment modified for foam forming from conventional water forming. According to the results, the shape of jet-to-wire ratios was the same in both forming methods, but in the case of foam forming, the achieved scale of jet-to-wire ratio and MD/CD-ratio were wider and not behaving sensitively to shear changes in the forming section as a water forming process would. This kind of behavior would be beneficial when upscaling foam technology to the production scale. The dryness results after the forming section indicated the improvement in dewatering, especially when foam density was at the lowest level (i.e., air content was at the highest level). In addition, the dryness results after the pressing section indicated a faster increase in the dryness level as a function of foam density, with all density levels compared to the corresponding water formed sheets. According to the study, the bonding level of water- and foam-laid structures were at the same level when the highest wet pressing value was applied. The results of the study show that the strength loss often associated with foam forming can be compensated for successfully through wet pressing.

Does kraft hardwood and softwood pulp viscosity correlate to paper properties?

TAPPI Journal ◽  
2016 ◽  
Vol 15 (10) ◽  
pp. 643-651 ◽  
Author(s):  
ROBERT J. OGLESBY ◽  
HUMPHREY J. MOYNIHAN ◽  
RICARDO B. SANTOS ◽  
ASHOK GHOSH ◽  
PETER W. HART
Keyword(s):  
Physical Properties ◽  
Strength Loss ◽  
Strength Properties ◽  
Clear Correlation ◽  
Paper Properties ◽  
Physical Strength ◽  
Pulp Viscosity ◽  
Softwood Pulp ◽  
The Impact ◽  
Related Paper

The impact of commercially prepared, fully bleached pulp viscosity variation on handsheet physical properties was evaluated at different levels of pulp refining. Hardwood pulps from the same brownstock species mix, cooking parameters, and kappa numbers were processed through two different commercial bleach plants: one with a D0(EP)D1D2 sequence and the second with an OD0(EOP)D1 sequence. Additionally, a commercial softwood (predominately Scotts pine) brownstock pulp bleached by an OD0(EP)D1D2 sequence was employed in this study. Pulps with viscosities ranging from 14 to 21 mPa∙s were refined in a Valley beater to two freeness levels, and the associated handsheet physical properties were measured in this study. Over the pulp viscosity range of 14 to 21 mPa∙s, no clear correlation was found to exist between pulp viscosity and related paper physical properties. Finally, a series of laboratory prepared bleached pulps were purposely prepared under non-ideal conditions to reduce their final viscosities to lower values. Handsheets made from these pulps were tested in their unbeaten condition for physical strength properties. Significant and rapid strength loss occurred when the measured pulp viscosity dropped below 12 mPa∙s; overall strength properties showed no correlation to viscosity above the critical 12 mPa∙s value.

The Analysis of Proprioception Alteration during First Five Months after Anterior Cruciate Ligament Reconstruction

2018 ◽  
Vol 1 (84) ◽  
Author(s):  
Vilma Jurevičienė ◽  
Albertas Skurvydas ◽  
Juozas Belickas ◽  
Giedra Bušmanienė ◽  
Dovilė Kielė ◽  
...  
Keyword(s):  
Anterior Cruciate Ligament ◽  
Angular Velocity ◽  
Knee Joint ◽  
Cruciate Ligament ◽  
Position Sense ◽  
Joint Position Sense ◽  
Joint Position ◽  
Starting Position ◽  
Angular Velocities ◽  
Anterior Cruciate

Research  background  and  hypothesis.  Proprioception  is  important  in  the  prevention  of  injuries  as  reduced proprioception  is  one  of  the  factors  contributing  to  injury  in  the  knee  joint,  particularly  the  ACL.  Therefore, proprioception appears not only important for the prevention of ACL injuries, but also for regaining full function after ACL reconstruction.Research aim. The aim of this study was to understand how proprioception is recovered four and five months after anterior cruciate ligament (ACL) reconstruction.Research methods. The study included 15 male subjects (age – 33.7 ± 2.49 years) who had undergone unilateral ACL reconstruction with a semitendinosus/gracilis (STG) graft in Kaunas Clinical Hospital. For proprioceptive assessment, joint position sense (JPS) was measured on both legs using an isokinetic dynamometer (Biodex), at knee flexion of 60° and 70°, and at different knee angular velocities of 2°/s and 10°/s. The patients were assessed preoperatively and after 4 and 5 months, postoperatively.Research results. Our study has shown that the JPS’s (joint position sense) error scores  to a controlled active movement is significantly higher in injured ACL-deficient knee than in the contralateral knee (normal knee) before surgery and after four and five months of rehabilitation.  After 4 and 5 months of rehabilitation we found significantly lower values in injured knees compared to the preoperative data. Our study has shown that in injured knee active angle reproduction errors after 4 and 5 months of rehabilitation were higher compared with the ones of the uninjured knee. Proprioceptive ability on the both legs was  independent of all differences angles for target and starting position for movement. The knee joint position sense on both legs depends upon the rate of two different angular velocities and the mean active angle reproduction errors at the test of angular velocity slow speed was the highest compared with the fast angular velocity. Discussion and conclusions. In conclusion, our study shows that there was improvement in mean JPS 4 and 5 months after ACL reconstruction, but it did not return to normal indices.Keywords: knee joint, joint position sense, angular velocity, starting position for movement.

Effect of Inner and Outer Wheels Driving Force Control on Small Electric Vehicle

2020 ◽  
Vol 17 (4) ◽  
pp. 8246-8254
Author(s):  
K. Shibazaki ◽  
H. Nozaki
Keyword(s):  
Control System ◽  
Angular Velocity ◽  
Electric Vehicle ◽  
Force Constant ◽  
Force Control ◽  
Driving Force ◽  
Vehicle Control ◽  
Steering Angle ◽  
Force Control System ◽  
The Difference

In this study, in order to improve steering stability during turning, we devised an inner and outer wheel driving force control system that is based on the steering angle and steering angular velocity, and verified its effectiveness via running tests. In the driving force control system based on steering angle, the inner wheel driving force is weakened in proportion to the steering angle during a turn, and the difference in driving force is applied to the inner and outer wheels by strengthening the outer wheel driving force. In the driving force control (based on steering angular velocity), the value obtained by multiplying the driving force constant and the steering angular velocity,  that differentiates the driver steering input during turning output as the driving force of the inner and outer wheels. By controlling the driving force of the inner and outer wheels, it reduces the maximum steering angle by 40 deg and it became possible to improve the cornering marginal performance and improve the steering stability at the J-turn. In the pylon slalom it reduces the maximum steering angle by 45 deg and it became possible to improve the responsiveness of the vehicle. Control by steering angle is effective during steady turning, while control by steering angular velocity is effective during sharp turning. The inner and outer wheel driving force control are expected to further improve steering stability.

System-in-Packages with Low Power Loss for Future Voltage Regulators

2010 ◽  
Vol 130 (9) ◽  
pp. 1630-1635
Author(s):  
Takayuki Hashimoto ◽  
Tetsuya Kawashima ◽  
Masaki Shiraishi ◽  
Noboru Akiyama ◽  
Tomoaki Uno ◽  
...  
Keyword(s):  
Low Power ◽  
Power Loss ◽  
Voltage Regulators
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