A Protocol for the Determination of Critical Speed as an Index of Swimming Endurance Performance

2015 ◽  
pp. 55-59 ◽  
Author(s):  
B. Wright ◽  
D.J. Smith
Keyword(s):  
Critical Speed ◽  
Endurance Performance ◽  
Swimming Endurance

New Methods of Calculation for the Determination of a Special Form of Instability of the Elastic Equilibrium of a Cantilever Wing

1940 ◽  
Vol 44 (359) ◽  
pp. 816-826 ◽  
Author(s):  
Tullio Viola
Keyword(s):  
Special Form ◽  
Critical Speed ◽  
Positive Characteristic ◽  
Elastic Equilibrium ◽  
New Methods ◽  
Methods Of Calculation ◽  
Characteristic Value ◽  
Plane Form

SummaryThe superposition of the flexural instability of the plane form of a cantilever wing in its own plane, over that of the torsional elastic equilibrium, gives rise to a special phenomenon of mixed instability which has been translated analytically by Prof. C. Minelli into the problem of determining the first positive characteristic value of a certain system of two ordinary, linear and homogeneous equations, in two unknown functions, with given limiting conditions. The methods of calculation, both analytical and numerical, for the solution of this problem are described. The results confirm the intuitive inferences according to which, other conditions being equal, the backward displacement of the elastic axis worsens conditions by lowering the critical speed.

scholarly journals Contribution to determination of critical speed and allowed speed of navigation for vessels in navigable canals

Tehnika ◽  
2020 ◽  
Vol 75 (1) ◽  
pp. 67-72
Author(s):  
Ivan Škiljaica ◽  
Vladimir Škiljaica
Keyword(s):  
Critical Speed

scholarly journals Iso-duration Determination of D′ and CS under Laboratory and Field Conditions

2017 ◽  
Vol 38 (07) ◽  
pp. 527-533 ◽  
Author(s):  
Christoph Triska ◽  
Bettina Karsten ◽  
Alfred Nimmerichter ◽  
Harald Tschan
Keyword(s):  
Body Mass ◽  
Exercise Test ◽  
Critical Speed ◽  
Time Trial ◽  
Time To Exhaustion ◽  
Time Model ◽  
Incremental Exercise Test ◽  
Laboratory Time ◽  
Level Of Agreement

AbstractWhilst Critical Speed (CS) has been successfully translated from the laboratory into the field, this translation is still outstanding for the related maximum running distance (D′). Using iso-duration exhaustive laboratory and field runs, this study investigated the potential interchangeable use of both parameters, D′ and CS. After an incremental exercise test, 10 male participants (age: 24.9±2.1 yrs; height: 180.8±5.8 cm; body mass: 75.3±8.6 kg; V̇ ˙VO2peak 52.9±3.1 mL∙min−1∙kg−1) performed 3 time-to-exhaustion runs on a treadmill followed by 3 exhaustive time-trial runs on a-400 m athletics outdoor track. Field time-trial durations were matched to their respective laboratory time-to-exhaustion runs. D′ and CS were calculated using the inverse-time model (speed=D′/t+CS). Laboratory and field values of D′ and CS were not significantly different (221±7 m vs. 225±72 m; P=0.73 and 3.75±0.36 m∙s−1 vs. 3.77±0.35 m∙s−1, P=0.68), and they were significantly correlated (r=0.86 and 0.94). The 95% LoA were ±75.5 m and ±0.24 m∙s−1 for D′ and CS, respectively. Applying iso-durations provides non-significant differences for D′ and CS and a significant correlation between conditions. This novel translation method can consequently be recommended to coaches and practitioners, however a questionable level of agreement indicates to use D′ with caution.

A New Frequency-Speed Diagram Weighted With Strength of Modes in Rotating Machinery

2008 ◽  
Author(s):  
Yun-Ho Seo ◽  
Chong-Won Lee
Keyword(s):  
Critical Speed ◽  
Rotor System ◽  
Operating Speed ◽  
Important Criterion ◽  
Generator System ◽  
Worst Case ◽  
Excitation Force ◽  
Matrix Norms ◽  
Forced Responses

The coincidence of operating speed and critical speed must be avoided in the design of a rotor system. If the rotor system has various critical speeds as well as many modes, the determination of dangerous modes is a first step of the design stages. In this paper, the use of a new frequency-speed diagram that displays the significance of modes in order to help the design and analysis of a rotor system is suggested. The diagram is a modified version of a waterfall chart. The method graphically shows the magnitude of the forced responses by the directional frequency response matrices in accordance with operating speed because the responses are the most important criterion to determine significance of modes. In addition, because the excitation force of a rotor system such as mass unbalances is not known before the completion of manufacturing, the concept of summation of matrix norms, which is more conservative than conventional H∞ norm, is used in order to consider the worst of the worst case. A simple rotor system and a real generator system, which has both anisotropy and asymmetry, are demonstrated for usefulness of the proposed diagrams. The information of the diagram is then used to analyze the dynamic characteristics of the generator system.

Experimental Determination of Rotor Foundation Parameters for Improved Critical Speed Predictions

1997 ◽  
Author(s):  
Jiankang Xu ◽  
John M. Vance
Keyword(s):  
Critical Speed ◽  
Dynamic Test ◽  
Element Model ◽  
Modal Damping ◽  
Matrix Codes ◽  
Foundation Parameters ◽  
Rotor Dynamic ◽  
Foundation Structure ◽  
Large Rotor

Measurements on a large rotor dynamic test rig in the Turbomachinery Laboratory with a concrete and steel foundation have shown some critical speeds which can only be predicted if the foundation is included in the model. Mobility transfer function measurements on the foundation were made to obtain the required parameters for including the foundation in the rotordynamic computer model. These measurements eliminate the necessity for building a large finite element model of the foundation structure and allow the use of fast transfer matrix codes for modeling rotor bearing systems which have strong foundation participation. A method first described by Nicholas was used to get a set of equivalent bearing coefficients from a combination of the foundation parameters with the true bearing coefficients. Measurements made by the present authors show that the modal damping of the foundation can be obtained easily from the mobility curves, and that the improved critical speed predictions can be obtained in some cases by using only one foundation mode to calculate the equivalent bearing coefficients.

Motivational self-talk improves time-trial swimming endurance performance in amateur triathletes

2020 ◽  
pp. 1-14
Author(s):  
Lorena Fernanda de Matos ◽  
Maurizio Bertollo ◽  
Joice Mara Facco Stefanello ◽  
Flávio Oliveira Pires ◽  
Caroline Kêmela da Silva ◽  
...  
Keyword(s):  
Time Trial ◽  
Endurance Performance ◽  
Self Talk ◽  
Swimming Endurance

The Residual Shaft Bow Effect on Dynamic Response of a Simply Supported Rotor With Disk Skew and Mass Unbalances

1989 ◽  
Vol 111 (2) ◽  
pp. 170-178 ◽  
Author(s):  
Ting Nung Shiau ◽  
En Kuan Lee
Keyword(s):  
Dynamic Response ◽  
Critical Speed ◽  
Thin Disk ◽  
Thick Disk ◽  
Square Root ◽  
Critical Mode ◽  
Simply Supported ◽  
Single Disk

The effect of residual shaft bow on the dynamic response of a simply supported single disk rotor with disk skew and mass unbalances is studied. The influence of disk-positioning between bearings also is investigated. Under the combined influences, the zero amplitude speed for a thin disk and the first zero amplitude speed for a thick disk are shown to be smaller than or equal to the square root of the ratio of residual bow amplitude to unbalance eccentricity. Moreover, when the rotor passes through the critical speed associated with disk pitch, the rotational amplitudes are greater than when it passes through the first translational critical mode. The results, shown in this study, can significantly assist in the determination of rotor unbalances.

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