scholarly journals MEASUREMENTS OF FORCES ON DOLOS ARMOR UNITS AT PROTOTYPE SCALE

1988 ◽  
Vol 1 (21) ◽  
pp. 174 ◽  
Author(s):  
Gary L. Howell
Keyword(s):  
Degrees Of Freedom ◽  
Bottom Layer ◽  
Core Material ◽  
Crescent City ◽  
Side Scan Sonar ◽  
Six Degrees Of Freedom ◽  
Wave Measurements ◽  
A Site ◽  
Wave Induced

In-situ measurements of the structural bending moments and torque about the shank-fluke interface of the dolos armor unit have been made for 42-ton (36-metric tonne) dolosse at Crescent City, California jetty. The measurements include the static loads on the dolosse as well as wave induced forces. The data were obtained from internal strain gages cast into the dolos during construction along with a special data acquisition system. The measurement system was also capable of capturing impact forces caused by dolos rocking or movement. Measurements were made during the winter storm seasons from January 1987 through May 1988. Coincident with the structural measurements, wave height and period were measured at several water depths approaching the breakwater, including a site directly in front of the dolos test section. The Crescent City jetty is a shallow water breakwater with depth limited waves in about 10 meters of water depth. The structural measurements were made from 14 dolos units arranged in a rectangular section on the top layer of the trunk portion of the jetty. Four of these dolosse are also instrumented with an accelerometer platform to measure motion with six degrees of freedom. In addition, there are three instrumented dolosse on the bottom layer of the breakwater. These dolosse measure the static stress due to the units placed on top of them, as well as pulsating forces. The structural and wave measurements, reported here, are supplemented with hydrostatic pore pressure measurements in the core material of the breakwater, and by aerial photogrammetric motion analysis (Kendall, 1988), land based surveys, boudary condition surveys, hydrographic surveys, and side scan sonar surveys.

A Six-Degree-of-Freedom Test System for the Study of Joint Mechanics and Ligament Forces

1995 ◽  
Vol 117 (4) ◽  
pp. 383-389 ◽  
Author(s):  
J. M. Hollis
Keyword(s):  
Degrees Of Freedom ◽  
Test System ◽  
Testing System ◽  
Joint Mechanics ◽  
Six Degrees Of Freedom ◽  
Position Feedback ◽  
Six Degree Of Freedom ◽  
Good Agreement

A joint testing system was designed to transmit a specified motion or force to a joint in all six degrees of freedom (d.o.f.) using a spatial linkage system for position feedback. The precise reproducibility of position provided by this method of position feedback allows determination of in situ ligament forces for external joint loadings. Load on the structure of interest is calculated from six d.o.f. load cell output after the loaded position is reproduced with all other structures removed. In a test of this system, measured loads showed good agreement with applied loads.

scholarly journals Pressure-Induced Jahn-Teller Switch in the Homoleptic Hybrid Perovskite [(CH3)2NH2]Cu(HCOO)3: Orbital Reordering by Unconventional Degrees of Freedom

2021 ◽  
Author(s):  
Rebecca Scatena ◽  
Michał Andrzejewski ◽  
Roger Johnson ◽  
Piero Macchi
Keyword(s):  
Phase Transition ◽  
Coordination Polymer ◽  
Degrees Of Freedom ◽  
X Ray Diffraction ◽  
Hybrid Perovskite ◽  
Jahn Teller ◽  
And Shifts ◽  
A Site ◽  
Structural Instabilities

<div> <p><b>Through in-situ, high-pressure x-ray diffraction experiments we have shown that the homoleptic perovskite-like coordination polymer [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]Cu(HCOO)<sub>3</sub> undergoes a pressure-induced orbital reordering phase transition above 5.20 GPa. This transition is distinct from previously reported Jahn-Teller switching in coordination polymers, which required at least two different ligands that crystallize in a reverse spectrochemical series. We show that the orbital reordering phase transition in [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]Cu(HCOO)<sub>3</sub> is instead primarily driven by unconventional octahedral tilts and shifts in the framework, and/or a reconfiguration of A-site cation ordering. These structural instabilities are unique to the coordination polymer perovskites, and may form the basis for undiscovered orbital reorientation phenomena</b><b> in this broad family of materials.</b><b></b></p> </div> <b><br></b>

Effect of Sensor Failure on Dynamometry Calibration

2020 ◽  
Author(s):  
Nicholas Vlajic ◽  
Michael Jonson ◽  
Manton Guers
Keyword(s):  
Degrees Of Freedom ◽  
Fluid Dynamic ◽  
Least Square ◽  
Elastic Model ◽  
Sensor Failure ◽  
Static Loads ◽  
Six Degrees Of Freedom ◽  
In Situ Calibration ◽  
Calibration Matrix

Abstract Dynamometers are used to measure integrated fluid dynamic loads such as thrust, torque or side forces. To resolve all of three force and three moment components, multiple embedded force gages are often used. Due to arrangement, static loads, and redundancy, the number of sensor channels can exceed the six degrees of freedom needed to resolve the generalized rigid body forces. This paper considers modeling of the force gages as simple springs to develop an elastic model of the dynamometer. The method was applied to a dynamometer consisting of six three-component force gages arranged in an axisymmetric ring. A calibration matrix based on the elastic model with individual force gage sensitivities was shown to match a full calibration matrix where properly summed force gage voltages were obtained under global load application. The elastic model was then extended to consider calibration matrices where sensors were assumed to fail. In this scenario, several virtual loads were applied to the dynamometer and the calibration matrix was obtained by minimizing the least square error. It was found that nearly half of the sensors could be lost and still a virtual calibration could be applied to the measurements. Extending the least square idea, an actual in-situ calibration matrix was formed by striking the dynamometer with a diverse set of instrumented hammer strikes. This calibration matrix also agreed with the other calibrations at frequencies below where system dynamics become important.

scholarly journals Pressure-Induced Jahn-Teller Switch in the Homoleptic Hybrid Perovskite [(CH3)2NH2]Cu(HCOO)3: Orbital Reordering by Unconventional Degrees of Freedom

2021 ◽  
Author(s):  
Rebecca Scatena ◽  
Michał Andrzejewski ◽  
Roger Johnson ◽  
Piero Macchi
Keyword(s):  
Phase Transition ◽  
Coordination Polymer ◽  
Degrees Of Freedom ◽  
X Ray Diffraction ◽  
Hybrid Perovskite ◽  
Jahn Teller ◽  
And Shifts ◽  
A Site ◽  
Structural Instabilities

<div> <p><b>Through in-situ, high-pressure x-ray diffraction experiments we have shown that the homoleptic perovskite-like coordination polymer [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]Cu(HCOO)<sub>3</sub> undergoes a pressure-induced orbital reordering phase transition above 5.20 GPa. This transition is distinct from previously reported Jahn-Teller switching in coordination polymers, which required at least two different ligands that crystallize in a reverse spectrochemical series. We show that the orbital reordering phase transition in [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]Cu(HCOO)<sub>3</sub> is instead primarily driven by unconventional octahedral tilts and shifts in the framework, and/or a reconfiguration of A-site cation ordering. These structural instabilities are unique to the coordination polymer perovskites, and may form the basis for undiscovered orbital reorientation phenomena</b><b> in this broad family of materials.</b><b></b></p> </div> <b><br></b>

Stepping Response During Constrained and Unconstrained Standing in Moving Environments

2014 ◽  
Vol 156 (A3) ◽  
Keyword(s):  
Degrees Of Freedom ◽  
Ecological Validity ◽  
Platform Motion ◽  
Six Degrees Of Freedom ◽  
Limited Experience ◽  
Wave Induced ◽  
Stepping Response ◽  
Platform Motions

The purpose of this study was to determine the differences in human stepping response reaction between constrained and unconstrained standing while being exposed to simulated wave-induced platform motions. Twenty subjects (10 male and 10 female), with limited experience recreating or working in motion-rich environments, performed a constrained and an unconstrained standing task on a six-degrees-of-freedom motion bed while being exposed to two different simulated platform motion conditions. Stepping occurrence was greater during unconstrained standing than constrained standing during all three motion conditions. However, no significant differences in platform kinematics were found between stepping cases. These results suggest that stepping occurs more frequently than originally hypothesized. As such, stepping should not be considered as a last resource when all fixed-support options have been exhausted. This should be taken into consideration to ensure ecological validity when developing models to predict stepping occurrence.

STEPPING RESPONSE DURING CONSTRAINED AND UNCONSTRAINED STANDING IN MOVING ENVIRONMENTS

2021 ◽  
Vol 156 (A3) ◽  
Author(s):  
C A Duncan ◽  
W J Albert ◽  
R G Langlois ◽  
S N MacKinnon
Keyword(s):  
Degrees Of Freedom ◽  
Ecological Validity ◽  
Platform Motion ◽  
Six Degrees Of Freedom ◽  
Limited Experience ◽  
Wave Induced ◽  
Stepping Response ◽  
Platform Motions

The purpose of this study was to determine the differences in human stepping response reaction between constrained and unconstrained standing while being exposed to simulated wave-induced platform motions. Twenty subjects (10 male and 10 female), with limited experience recreating or working in motion-rich environments, performed a constrained and an unconstrained standing task on a six-degrees-of-freedom motion bed while being exposed to two different simulated platform motion conditions. Stepping occurrence was greater during unconstrained standing than constrained standing during all three motion conditions. However, no significant differences in platform kinematics were found between stepping cases. These results suggest that stepping occurs more frequently than originally hypothesized. As such, stepping should not be considered as a last resource when all fixed-support options have been exhausted. This should be taken into consideration to ensure ecological validity when developing models to predict stepping occurrence.

scholarly journals ANALYSIS OF 42-TON DOLOS MOTIONS AT CRESCENT CITY

1988 ◽  
Vol 1 (21) ◽  
pp. 158 ◽  
Author(s):  
Thomas R. Kendall
Keyword(s):  
Boundary Conditions ◽  
Structural Design ◽  
Monitoring Program ◽  
Design Criteria ◽  
Relative Importance ◽  
Crescent City ◽  
Side Scan Sonar ◽  
Wave Measurements ◽  
Monitoring Effort

Photogrammetry has been applied to make precise measurements of post-construction displacements of 38.2-metric ton (42-ton) dolosse on the outer breakwater at Crescent City, California. Data from two storm seasons are currently available from this monitoring program which was initiated in November 1986 and which is expected to continue at least through the next three winters. Supplemented by conventional land surveys, wave measurements, aerial inspections, and side scan sonar underwater imagery, observations from the photogrammetric monitoring have led to several preliminary conclusions regarding regions of relatively large dolos movement, dolos nesting, the dependency on breakwater slope of uprush or drawdown dominated armor unit movement, and the relative importance of armor unit movement and boundary conditions in dolos breakage. This paper describes the methods used for, and results obtained from, this monitoring effort along with the application of these results to a Corps study (Howell, 1988) Whose objective is to develop structural design criteria for the dolos concrete armor unit.

Influence of Wave-Induced Skid Motions on the Launch of Free-Fall Skid Lifeboats From Floating Hosts: Experimental and Numerical Investigations

2014 ◽  
Author(s):  
Neil Luxcey ◽  
Svein-Arne Reinholdtsen ◽  
Thomas Sauder ◽  
Sébastien Fouques ◽  
Jingzhe Jin ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Model Test ◽  
Degrees Of Freedom ◽  
Free Fall ◽  
Weather Conditions ◽  
Norwegian Sea ◽  
Six Degrees Of Freedom ◽  
Offshore Installations ◽  
Storm Condition ◽  
Wave Induced

The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations. This paper investigates the effects of the wave-induced skid motion on the launch of free-fall lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.

Simultanous Mapping and Localization of Rescue Environments (Gleichzeitiges Kartieren und Lokalisieren von Rescue-Umgebungen)

2005 ◽  
Vol 47 (5) ◽  
Author(s):  
Hartmut Surmann ◽  
Kai Pervölz ◽  
Andreas Nüchter ◽  
Kai Lingemann ◽  
Joachim Hertzberg ◽  
...  
Keyword(s):  
Mobile Robot ◽  
Degrees Of Freedom ◽  
Urban Setting ◽  
Robotic Systems ◽  
Six Degrees Of Freedom ◽  
Rescue Robot ◽  
Rescue Workers ◽  
Robot Systems ◽  
A Site ◽  
Remote Inspection

SummaryDeploying rescue workers in an urban setting is often a perilous, time-, power-, and force-consuming job, and robot systems to assist in this effort are needed. A fundamental task for rescuer is to localize and salvage injured persons. To this end, robotic systems are used for mapping a site and for remote inspection of suspicious objects. The mobile robot Kurt3D is the first rescue robot that is capable of mapping its environment in 3D and self localize in all six degrees of freedom, i. e., considering its

Sign in / Sign up

Export Citation Format

Share Document