Dynamical overloading of lifting appliances submitted to vertical movements: use of one degree of freedom oscillating systems, equivalent to two degrees of freedom systems

2007 ◽  
Vol 30 (1/2/3) ◽  
pp. 141
Author(s):  
Silvio Matteazzi ◽  
Ferdinando Minoia
Keyword(s):  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Vertical Movements ◽  
Two Degrees Of Freedom ◽  
Oscillating Systems

Strouhal Number for VIV Excitation of Long Slender Structures

2018 ◽  
Author(s):  
Andrew E. Potts ◽  
Douglas A. Potts ◽  
Hayden Marcollo ◽  
Kanishka Jayasinghe
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Degrees Of Freedom ◽  
Measurement Techniques ◽  
Cross Flow ◽  
Degree Of Freedom ◽  
Circular Cylinders ◽  
Two Degrees Of Freedom ◽  
Shedding Frequency ◽  
Eddy Shedding

The prediction of Vortex-Induced Vibration (VIV) of cylinders under fluid flow conditions depends upon the eddy shedding frequency, conventionally described by the Strouhal Number. The most commonly cited relationship between Strouhal Number and Reynolds Number for circular cylinders was developed by Lienhard [1], whereby the Strouhal Number exhibits a consistent narrow band of about 0.2 (conventional across the sub-critical Re range), with a pronounced hump peaking at about 0.5 within the critical flow regime. The source data underlying this relationship is re-examined, wherein it was found to be predominantly associated with eddy shedding frequency about fixed or stationary cylinders. The pronounced hump appears to be an artefact of the measurement techniques employed by various investigators to detect eddy-shedding frequency in the wake of the cylinder. A variety of contemporary test data for elastically mounted cylinders, with freedom to oscillate under one degree of freedom (i.e. cross flow) and two degrees of freedom (i.e. cross flow and in-line) were evaluated and compared against the conventional Strouhal Number relationship. It is well established for VIV that the eddy shedding frequency will synchronise with the near resonant motions of a dynamically oscillating cylinder, such that the resultant bandwidth of lock-in exhibits a wider range of effective Strouhal Numbers than that reflected in the narrow-banded relationship about a mean of 0.2. However, whilst cylinders oscillating under one degree of freedom exhibit a mean Strouhal Number of 0.2 consistent with fixed/stationary cylinders, cylinders with two degrees of freedom exhibit a much lower mean Strouhal Number of around 0.14–0.15. Data supports the relationship that Strouhal Number does slightly diminish with increasing Reynolds Number. For oscillating cylinders, the bandwidth about the mean Strouhal Number value appears to remain largely consistent. For many practical structures in the marine environment subject to VIV excitation, such as long span, slender risers, mooring lines, pipeline spans, towed array sonar strings, and alike, the long flexible cylinders will respond in two degrees of freedom, where the identified difference in Strouhal Number is a significant aspect to be accounted for in the modelling of its dynamic behaviour.

Design and Evaluation of a Multi-Degree-of-Freedom Foot/Pedal Interface for Cycling

1992 ◽  
Vol 8 (2) ◽  
pp. 152-164 ◽  
Author(s):  
Dennis Wootten ◽  
Maury L. Hull
Keyword(s):  
Knee Joint ◽  
Significant Interaction ◽  
Degrees Of Freedom ◽  
Knee Injuries ◽  
Degree Of Freedom ◽  
Two Degrees Of Freedom ◽  
Factors Affecting ◽  
Freedom Of Movement ◽  
Sample Data ◽  
Comprehensive Study

Described is the design of a foot/pedal interface intended as a research tool in the study of overuse knee injuries in cycling. The interface enables the systematic variation of factors that may affect loads transmitted by the knee joint. It permits two degrees of freedom of movement, inversion/eversion and abduction/adduction rotations, either separately or in combination. The movement permitted by each degree of freedom can be either free or resisted by spring assemblies. Sample data were collected to demonstrate the function of the foot/pedal interface. With no spring resistance, the interface functioned as intended by allowing free movement of the foot. Significant interaction was seen between the two degrees of freedom, with more motion and a larger absolute mean occurring when both degrees of freedom were allowed simultaneously. This emphasizes the need for a multi-degree-of-freedom interface when undertaking a comprehensive study of the factors affecting loads transmitted by the knee.

A guide to classical flutter

1988 ◽  
Vol 92 (919) ◽  
pp. 339-355 ◽  
Author(s):  
L. T. Niblett
Keyword(s):  
Degrees Of Freedom ◽  
Normal Modes ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Structural Coupling ◽  
Two Degrees Of Freedom ◽  
Single Degree ◽  
Lifting Surface ◽  
Classical Flutter ◽  
Comprehensive Study

Summary First essentials of classical flutter are demonstrated by a comprehensive study of the behaviour of a lifting surface with two degrees of freedom under the action of airforces limited to those in phase with displacement. Structural coupling between the coordinates is eliminated by taking the normal modes to be the deflection coordinates, and this results in conditions for stability with particularly concise forms. It is shown that the flutter stability can be seen to be very much a matter of the relative amplitudes of heave and pitch in the normal modes. In-quadrature airforces are then introduced and it is shown that they have little effect when the flutter is severe. They are of more importance in the milder forms of flutter, the extreme of which are shown to be little different from instabilities in a single degree of freedom.

Trajectories Generated by a Novel Cam Driven Five-Bar Mechanism

2015 ◽  
Vol 799-800 ◽  
pp. 685-692
Author(s):  
Shinn Liang Chang ◽  
Dai Jia Juan ◽  
You Huang Syu
Keyword(s):  
Degrees Of Freedom ◽  
Trajectory Generation ◽  
Special Kind ◽  
Degree Of Freedom ◽  
Two Degrees Of Freedom ◽  
Different Types

In industry, the special kind of trajectory is often designed to fit the desired motion required. In literature, four-bar mechanism is popularly applied and well studied in the trajectory generation. Different types of trajectories are generated by the choose of the ratio of links. The five-bar mechanism is another popular one to generate the desired trajectory and it is more flexible due to it has two degrees of freedom. The geared five-bar mechanism is then commonly used by reducing the degree of freedom of the mechanism into one by implied one pair of gear. In this study, the trajectories generated by a novel cam driven five-bar mechanism proposed by the authors are investigated. It could supply more choices in the application of trajectory generation.

Efficient simultaneous dense coding and teleportation with two-photon four-qubit cluster states

2016 ◽  
Vol 14 (05) ◽  
pp. 1650023 ◽  
Author(s):  
Cai Zhang ◽  
Haozhen Situ ◽  
Qin Li ◽  
Guang Ping He
Keyword(s):  
Degrees Of Freedom ◽  
Quantum States ◽  
Degree Of Freedom ◽  
Generation Rate ◽  
Entangled States ◽  
Dense Coding ◽  
Cluster States ◽  
Two Degrees Of Freedom ◽  
Classical Information ◽  
Two Photon

We firstly propose a simultaneous dense coding protocol with two-photon four-qubit cluster states in which two receivers can simultaneously get their respective classical information sent by a sender. Because each photon has two degrees of freedom, the protocol will achieve a high transmittance. The security of the simultaneous dense coding protocol has also been analyzed. Secondly, we investigate how to simultaneously teleport two different quantum states with polarization and path degree of freedom using cluster states to two receivers, respectively, and discuss its security. The preparation and transmission of two-photon four-qubit cluster states is less difficult than that of four-photon entangled states, and it has been experimentally generated with nearly perfect fidelity and high generation rate. Thus, our protocols are feasible with current quantum techniques.

On the Mechanical Efficiency of Differential Gearing

1985 ◽  
Vol 107 (1) ◽  
pp. 61-67 ◽  
Author(s):  
D. Yu ◽  
N. Beachley
Keyword(s):  
Analytical Methods ◽  
Degrees Of Freedom ◽  
Computer Programming ◽  
Mechanical Efficiency ◽  
Input Power ◽  
Degree Of Freedom ◽  
Two Degrees Of Freedom ◽  
Power Coupling ◽  
Continuously Variable Transmissions ◽  
Full Utilization

Although much work has been done on the efficiency of epicyclic gearing, emphasis has usually been given to the planetary that has only one degree of freedom. In this paper, a thorough study of the efficiency of differential gearing that has two degrees of freedom is presented. New analytical methods and programs are designed to calculate differential efficiencies and to plot useful curves. Examples are given for split-path differential, continuously variable transmissions (CVT) with input power coupling. It is pointed out that there are six different ways of using a given differential design in such a split-path CVT, providing the opportunity for full utilization of its potential. With the help of computer programming, optimum designs can be obtained.

The Dynamic Analysis and Design of Relatively Flexible Cam Mechanisms Having More Than One Degree of Freedom

1959 ◽  
Vol 81 (4) ◽  
pp. 323-331 ◽  
Author(s):  
R. C. Johnson
Keyword(s):  
Dynamic Analysis ◽  
Numerical Method ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
General Analysis ◽  
Two Degrees Of Freedom ◽  
Analysis And Design ◽  
Significant Figures ◽  
Cam Systems ◽  
General Method

The author presents a simple numerical method for analyzing and designing cam systems which have more than one degree of freedom. Illustrative examples are given for follower systems having two degrees of freedom. In addition to the general analysis and design methods which are derived, the examples also illustrate the importance of significant figures in the calculating procedure and the importance of the consideration of the distribution of mass throughout elastic regions. The general method of analysis and design can be extended to follower systems having more degrees of freedom than two.

A 7R-Based, Two Degrees of Freedom Robomech

2000 ◽  
Author(s):  
Ahmad A. Smaili
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Architecture ◽  
Degree Of Freedom ◽  
Robot Arm ◽  
End Effector ◽  
Kinematic Constraints ◽  
Two Degrees Of Freedom ◽  
Synthesis Procedure ◽  
Two Degree Of Freedom

Abstract A robomech is a crossbreed of a mechanism and a robot arm. It has a parallel architecture equipped with more than one end effector to accomplish tasks that require the coordination of many functions. Robomechs with multi degrees of freedom that are based on the 4R and 5R chains have found their way into the literature. This article presents a new, two-degree of freedom robomech whose architecture is based on the 7R chain. The robomech is capable of performing two-function tasks. The features, kinematic constraints, and synthesis procedure of the robomech are outlined and an application example is given.

scholarly journals On Structural Patterns of Mechanical Systems with Impacts with One and Two Degrees-of-Freedom

2013 ◽  
Vol 2013 ◽  
pp. 1-22 ◽  
Author(s):  
Barbara Blazejczyk-Okolewska
Keyword(s):  
Degrees Of Freedom ◽  
Matrix Representation ◽  
Mechanical Systems ◽  
Degree Of Freedom ◽  
Two Degrees Of Freedom ◽  
Structural Patterns ◽  
General Method

Structural patterns of mechanical systems with impacts with one degree-of-freedom and two degrees-of-freedom, with elastic connections, have been identified and described. For their identification, a general method proposed by the author has been applied. This method uses (i) a matrix representation of the system with impacts, (ii) procedures that enable generations of all combinations of such systems as well as their identification and elimination of redundant equivalent combinations, and (iii) a procedure for elimination of disconnected systems.

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