Measurement of Skier-Generated Forces during Roller-Ski Skating

This paper describes a system that was developed to measure ski pole and roller-ski reaction forces in three dimensions during roller-ski skating. Uni-axial force transducers mounted in the right and left ski poles measure axial loading of the poles. Six transducers in one roller-ski measure biaxial loads beneath the foot. A remote computer stores the amplified transducer signals transmitted from the skier through 100 m cables. Three-dimensional video-graphy determines the orientations of the poles and roller-ski in order to resolve the resultant poling and skating forces into three components. Calibration data suggest that the resolution of the force measurement system is ±3 to 9% of the actual poling and skating forces, respectively. Sample data are presented from a VI skating trial during roller-skiing. These data provide the first glimpse at the major functions of the upper and lower body during roller-ski skating and show how the tool could be used to examine the size and effectiveness of skier-generated forces.

Download Full-text

Fabrication of a Three-dimensional Force Measurement System Using Double Series Magnetic Suspension

IFAC-PapersOnLine ◽

10.1016/j.ifacol.2016.10.657 ◽

2016 ◽

Vol 49 (21) ◽

pp. 536-540 ◽

Cited By ~ 2

Author(s):

Takeshi Mizuno ◽

Yuji Ishino ◽

Masaya Takasaki

Keyword(s):

Measurement System ◽

Force Measurement ◽

Three Dimensional ◽

Double Series ◽

Magnetic Suspension ◽

Force Measurement System

Download Full-text

The three-dimensional stable mandibular landmarks in patients between the ages of 12.5 to 17.1 years

10.21203/rs.3.rs-16039/v1 ◽

2020 ◽

Author(s):

Gui Chen ◽

Mona Al Awadi ◽

David William Chambers ◽

Manuel O Lagravère-Vich ◽

Tianmin Xu ◽

...

Keyword(s):

Three Dimensional ◽

Growth Period ◽

Mandibular Canal ◽

Mental Foramen ◽

Three Dimensions ◽

Head Orientation ◽

Facial Growth ◽

Linear Distance ◽

The Right ◽

Stable Structures

Abstract Background: With the aid of implants, Björk identified the two-dimensional mandibular stable structures in cephalogram during facial growth. However, we don't know the three-dimensional stable structures exactly. The purpose of this study was to identify the most stable mandibular landmarks in growing patients using three-dimensional images.Methods: The sample was comprised of two cone-beam computed tomography (CBCT) scans taken about 4.6 years apart in 20 growing patients between the ages of 12.5 (T1) to 17.1 years (T2). After head orientation, landmarks were located on the chin (Pog), internal symphysis (Points C, D and E), and mandibular canals, which included the mental foramina (MF and MFA) and mandibular foramina (MdF). The linear distance change between Point C and these landmarks was measured on each CBCT to test stability through time. The reliability of the suggested stable landmarks was also evaluated. Results: The total distance changes between Point C and points D, E, Pog, MF, and MFA were all less than 1.0 mm from T1 to T2. The reliability measures of these landmarks, which were measured by the Cronbach alpha, were above 0.94 in all three dimensions for each landmark. From T1 to T2, distance changes from Point C to the right and left mandibular foramina were respectively 3.39±3.29 mm and 3.03±2.83 mm. Conclusions: During a growth period that averaged 4.6-years, ranging from 11.2 to 19.8 years, the structures that appeared relatively stable and could be used in mandibular regional superimposition included Pog, landmarks on the inferior part of the internal symphysis, and the mental foramen. The centers of the mandibular foramina, the starting points of the mandibular canal, underwent significant changes in the transverse and sagittal dimensions.

Download Full-text

Extrapolating and interpolating surfaces in depth

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1985.0020 ◽

1985 ◽

Vol 224 (1234) ◽

pp. 43-56 ◽

Cited By ~ 27

Keyword(s):

Three Dimensional ◽

Surface Orientation ◽

Three Dimensions ◽

Apparent Depth ◽

Right Hand ◽

Pictorial Cues ◽

Random Dot Stereograms ◽

Sloping Surface ◽

The Right ◽

Hand Image

Random -dot stereograms were generated with a blank area placed in part of the right-hand image so making a patchwork of monocular and binocular areas. The perceived depth and shape of the monocular region, where depth was not explicitly marked, depended in p art on the depth and surface orientation of adjacent binocular areas. Thus a monocular rectangle flanked by two binocular rectangles which were placed in different fronto-parallel planes was seen as a sloping surface spanning the depth between the binocular regions, and, under some conditions, the gradient of a sloping binocular plane extended into a neighbouring monocular area. Division of the monocular region into two by textural discontinuities or discontinuities of motion sometimes altered the shape of the extrapolated surface. Often, though, the shape was unchanged by such discontinuities implying that both two- and three-dimensional features are used to segment a scene into separate surfaces. Pictorial cues also contribute to the shape and apparent depth of the monocular surface. For instance, when subjects viewed a display consisting of portions of a cube of which two ends were shown stereoscopically and one side monocularly, the monocular side was seen in three dimensions filling the gap between the ends. When stereo cues were pitted against pictorial cues, sometimes pictorial cues and sometimes stereo cues dominated, and sometimes the surface contained sharp discontinuities enabling both to be accommodated.

Download Full-text

Design of Circular Cross-Section Corner-Filleted Flexure Hinges for Three-Dimensional Compliant Mechanisms

Journal of Mechanical Design ◽

10.1115/1.1480022 ◽

2002 ◽

Vol 124 (3) ◽

pp. 479-484 ◽

Cited By ~ 64

Author(s):

Nicolae Lobontiu ◽

Jeffrey S. N. Paine

Keyword(s):

Cross Section ◽

Compliant Mechanisms ◽

Compliant Mechanism ◽

Three Dimensional ◽

Circular Cross Section ◽

Axial Loading ◽

Flexure Hinge ◽

Flexure Hinges ◽

Element Simulation ◽

The Right

The paper introduces the circular cross-section corner-filleted flexure hinges as connectors in three-dimensional compliant mechanism applications. Compliance factors are derived analytically for bending, axial loading and torsion. A circular cross-section corner-filleted flexure hinge belongs to a domain delimited by the cylinder (no fillet) and the right circular cross-section flexure hinge (maximum fillet radius). The analytical model predictions are confirmed by finite element simulation and experimental measurements. The circular cross-section corner-filleted flexure hinges are characterized in terms of their compliance, precision of rotation and stress levels.

Download Full-text

Stereograms to aid group recognition and trend identification in vegetation data

Canadian Journal of Botany ◽

10.1139/b78-020 ◽

1978 ◽

Vol 56 (2) ◽

pp. 162-165 ◽

Cited By ~ 8

Author(s):

P. Fewster ◽

L. Orlóci

Keyword(s):

Three Dimensional ◽

Three Dimensions ◽

Simple Method ◽

Sample Points ◽

Left Image ◽

Dimensional Object ◽

The Right ◽

Trend Identification ◽

Dimensional Picture

When vegetation data are summarized on the basis of some method of ordination, a search for distinct groups or trends is greatly facilitated if the cloud of sample points is viewed under a lens stereoscope in three dimensions. The present paper describes a simple method to construct stereograms and illustrates their application in a classification problem.A stereogram is composed of two images of a three-dimensional object. The left image and the right correspond respectively to sightings with the left eye or the right eye of the observer. The diagrams are placed side by side at a specified distance apart, and when viewed with the aid of a stereoscope, the images will merge resulting in a three-dimensional picture.

Download Full-text

A Sensor System to Measure Force Applications of a Brace for Pectus carinatum

Journal of Medical Devices ◽

10.1115/1.4041190 ◽

2018 ◽

Vol 13 (1) ◽

Cited By ~ 1

Author(s):

Tomasz Bugajski ◽

Douglas Kondro ◽

Kartikeya Murari ◽

Janet Ronsky

Keyword(s):

Force Feedback ◽

Force Measurement ◽

Three Dimensional ◽

Compressive Force ◽

Current Treatment ◽

Sensor System ◽

Pectus Carinatum ◽

Applied Forces ◽

Human Participants ◽

Force Measurement System

Pectus carinatum (PC) presents itself as a protrusion on the chest wall of adolescent individuals. Current treatment for PC is performed with a Pectus carinatum orthosis (PCO) that applies a compressive force to the protrusion. While this treatment is accepted, the magnitude of compressive forces applied remains unknown leading to excessive or deficient compression. Although the need for this quantitative data is recognized, no studies reporting the data or methods are available. The purpose of this study was to design an accurate force measurement system (FMS) that could be incorporated into a PCO with minimal bulk. Components of the FMS were three-dimensional (3D)-printed and incorporated into an existing PCO design. The FMS was calibrated using a custom indenter that applied forces to the FMS in a controlled manner. Evaluation of the FMS on five human participants was also performed. A reliability measure of the FMS was calculated for analysis. The FMS was implemented into the PCO and able to withstand the applied forces. The calibration revealed an increase in load cell error with increased magnitude of applied force (mean error [SD] = 5.59 N [6.48 N]). Participants recruited to evaluate the FMS demonstrated reliable forces (R = 96%) with smaller standard deviations than those during the calibration. The FMS was shown capable of measuring PCO forces but requires further testing and improvement. This system is the foundational component in a wireless, minimalistic sensor system to provide real time force feedback to both the clinician and patient.

Download Full-text

Reliability and Validity of Kinetic and Kinematic Parameters Determined With Force Plates Embedded Under a Soil-Filled Baseball Mound

Journal of Applied Biomechanics ◽

10.1123/jab.2016-0117 ◽

2017 ◽

Vol 33 (4) ◽

pp. 305-310

Author(s):

Toshimasa Yanai ◽

Akifumi Matsuo ◽

Akira Maeda ◽

Hiroki Nakamoto ◽

Mirai Mizutani ◽

...

Keyword(s):

Force Measurement ◽

Reliability And Validity ◽

Repeated Measurements ◽

Kinematic Parameters ◽

Entire Duration ◽

Coefficients Of Variation ◽

Maximum Effort ◽

Reaction Forces ◽

Force Measurement System ◽

True Values

We developed a force measurement system in a soil-filled mound for measuring ground reaction forces (GRFs) acting on baseball pitchers and examined the reliability and validity of kinetic and kinematic parameters determined from the GRFs. Three soil-filled trays of dimensions that satisfied the official baseball rules were fixed onto 3 force platforms. Eight collegiate pitchers wearing baseball shoes with metal cleats were asked to throw 5 fastballs with maximum effort from the mound toward a catcher. The reliability of each parameter was determined for each subject as the coefficient of variation across the 5 pitches. The validity of the measurements was tested by comparing the outcomes either with the true values or the corresponding values computed from a motion capture system. The coefficients of variation in the repeated measurements of the peak forces ranged from 0.00 to 0.17, and were smaller for the pivot foot than the stride foot. The mean absolute errors in the impulses determined over the entire duration of pitching motion were 5.3 N˙s, 1.9 N˙s, and 8.2 N˙s for the X-, Y-, and Z-directions, respectively. These results suggest that the present method is reliable and valid for determining selected kinetic and kinematic parameters for analyzing pitching performance.

Download Full-text

Design and Calibration of a Tri-Directional Contact Force Measurement System

Applied Sciences ◽

10.3390/app11020877 ◽

2021 ◽

Vol 11 (2) ◽

pp. 877

Author(s):

Rizwan Ahmed ◽

Christian Maria Firrone ◽

Stefano Zucca

Keyword(s):

Contact Force ◽

Measurement System ◽

Force Measurement ◽

Three Dimensional ◽

Dynamic Contact ◽

Forced Response ◽

Contact Forces ◽

Blade Vibration ◽

Contact Models ◽

Force Measurement System

In low pressure turbine stages, adjacent blades are coupled to each other at their tip by covers, called shrouds. Three-dimensional periodic contact forces at shrouds strongly affect the blade vibration level as energy is dissipated by friction. To validate contact models developed for the prediction of nonlinear forced response of shrouded blades, direct contact force measurement during dynamic tests is mandatory. In case of shrouded blades, the existing unidirectional and bi-directional contact force measurement methods need to be improved and extended to a tri-directional measurement of shroud contact forces for a comprehensive and more reliable validation of the shroud contact models. This demands an accurate and robust measurement solution that is compatible with the nature and orientation of the contact forces at blade shrouds. This study presents a cost effective and adaptable tri-directional force measurement system to measure static and dynamic contact forces simultaneously in three directions at blade shrouds during forced response tests. The system is based on three orthogonal force transducers connected to a reference block that will eventually be put in contact with the blade shroud in the test rig. A calibration process is outlined to define a decoupling matrix and its subsequent validation is demonstrated in order to evaluate the effectiveness of the measurement system to measure the actual contact forces acting on the contact.

Download Full-text

Postoperative volume increase of facial soft tissue after percutaneous versus endonasal osteotomy technique in rhinoplasty using 3D stereophotogrammetry

Rhinology Journal ◽

10.4193/rhino10.056 ◽

2011 ◽

Vol 49 (1) ◽

pp. 121-126

Author(s):

B. van Loon ◽

N. van Heerbeek ◽

T.J.J. Maal ◽

W.A. Borstlap ◽

K.J.A.O. Ingels ◽

...

Keyword(s):

Soft Tissue ◽

Three Dimensional ◽

Measurement Data ◽

Three Dimensions ◽

Rank Test ◽

Facial Soft Tissue ◽

Osteotomy Technique ◽

3D Stereophotogrammetry ◽

Soft Tissue Changes ◽

The Right

BACKGROUND: When lateral osteotomies are performed as part of a rhinoplasty, the nose and paranasal region invariably change in three dimensions. The PURPOSE of this study is to compare the effect of the percutaneous perforating and endonasal continuous osteotomy techniques concerning the degree of postoperative swelling using three dimensional (3D) stereophotogrammetry. METHODOLOGY: A prospective follow-up study was conducted. Patients requiring bilateral osteotomies were included and randomly underwent a percutaneous osteotomy on one side and an endonasal osteotomy on the other side. Pre- and postoperative 3D photos were acquired using 3D stereophotogrammetry. Volumetric measurement data were acquired from the paranasal region using 3D software. Measurements were compared using Student`s t-test and Wilcoxon signed rank test statistics. RESULTS: Twenty patients were included. A percutaneous osteotomy was performed on the right side in nine patients and on the left side in 11 patients. The total volume, the volume of the right paranasal and left paranasal region were significantly larger postoperative. No difference was found between the sides. CONCLUSIONS: No difference concerning swelling is found between the percutaneous and endonasal osteotomy technique sides. With 3D stereophotogrammetry volumetric data can be acquired and compared to evaluate soft-tissue changes.

Download Full-text