How Simplifying Assumptions Affect the Computation of Three-Dimensional Knee Loads in Cycling

2001 ◽  
Author(s):  
Colin S. Gregersen ◽  
M. L. Hull
Keyword(s):  
Knee Injury ◽  
Knee Injuries ◽  
Three Dimensional ◽  
Simplifying Assumptions ◽  
D Model

Abstract Determining the force and moment components transmitted by the knee is useful both to understand the etiology of over-use knee injuries common in cycling [1] and also to assess how well different interventions protect against over-use injury. Because the loads thought to be primarily responsible for over-use knee injury are the non-driving moments (varus/valgus and internal/external axial moments) transmitted by the knee [2], a 3-D model is necessary for calculating these loads. To our knowledge, no study has developed a model that includes complete 3-D kinematics of the segments to calculate these loads. Consequently one objective of this study was to develop a complete, 3-D model to calculate the intersegmental knee loads during cycling. A second objective was to use this model to examine how simplifying assumptions affect the 3-D knee loads.

scholarly journals An Investigation of Knee Injury Profiles among Iranian Elite Karatekas: Observations from a Cross-Sectional Study

2021 ◽  
Vol 18 (13) ◽  
pp. 6888
Author(s):  
Hamidreza Naserpour ◽  
Julien S. Baker ◽  
Amir Letafatkar ◽  
Giacomo Rossettini ◽  
Frédéric Dutheil
Keyword(s):  
Knee Injury ◽  
Cruciate Ligament ◽  
Knee Injuries ◽  
Cross Sectional Study ◽  
Lower Extremity Injury ◽  
Sectional Study ◽  
Positive Health ◽  
Sports Activity ◽  
Cross Sectional ◽  
National Team

Karate training, despite the many positive health benefits, carries a risk of injury for participants. The current cross-sectional study aimed to investigate knee injury profiles among Iranian elite karatekas. Participants who attended the national team qualifiers, which included 390 male Kumite karatekas (age 24 ± 3 years old and weight 63 ± 12 kg), participated in this study. Information on knee injuries (injury history, type of injury mechanisms, and effects of knee symptoms on the ability to perform daily activities and recreational activities) were obtained using the Knee Outcome Survey (KOS). Using Pearson’s correlation coefficient, the study examined the relationships between different variables, including KOS subscales and levels of self-reported knee joint function. Our findings indicated that 287 karatekas (73.6%) experienced knee injuries. The anterior cruciate ligament (ACL) rupture (6.9%), articular cartilage (5.4%), and meniscus damage (3.8%) were the main typology of injury. In addition, there were no differences in knee injuries between the non-dominant and dominant legs. Most injuries occurred during the preparatory period (n = 162, 50%), especially during training periods. The KOS subscales scores (Mean ± Sd) for activities of daily living (ADL) and sports activity (SAS) were, respectively, 89 ± 11 and 91 ± 9. The self-reported scores for both the ADL and SAS subscales were, respectively, 89 ± 11 and 90 ± 10. Pearson coefficients of ADL and SAS subscales with their self-reported score were r = 0.761 (p < 0.0001) and r = 0.782 and (p < 0.0001), respectively. The profile of knee injuries in the current investigation is similar to previous surveys that reported lower extremity injury patterns. The findings of this study could be adopted to inform practice aimed at planning interventions for the reduction and prevention of knee injuries among karatekas.

scholarly journals Short-term recovery of physical activity and knee function after an acute knee injury

2020 ◽  
Vol 6 (1) ◽  
pp. e000950
Author(s):  
Sanne Fomin ◽  
Håkan Gauffin ◽  
Joanna Kvist
Keyword(s):  
Physical Activity ◽  
Knee Injury ◽  
Knee Injuries ◽  
Acl Injury ◽  
Knee Function ◽  
Physical Activity Participation ◽  
Activity Participation ◽  
Acute Knee ◽  
Acute Knee Injury

ObjectivesTo describe self-reported knee function, participation in physical activity and the number of knee surgeries at 3 and 6 months following acute knee injury.MethodsProspective cohort study. Participants, aged 15–40 years with an acute knee injury sustained no more than 6 weeks prior to inclusion, were recruited. There were 279 participants with ACL injury and 101 participants with other acute knee injuries included. Follow-up questionnaires were sent at 3 and 6 months after injury. Demographic information, activity participation, International Knee Documentation Committee subjective knee form (IKDC-SKF) and the Single Assessment Numeric Evaluation (SANE) score were collected. Additional knee injuries were obtained from self-report and medical charts.ResultsThe IKDC-SKF, SANE and physical activity participation were reduced at 3-month and 6-month follow-up. The number of participants who achieved health-promoting physical activity levels was reduced by 50% at 6-month follow-up compared with before injury. Seventeen per cent of participants with ACL injury and 41% of participants with other acute knee injuries had returned to their preinjury physical activity at 6 months. Participants with ACL injury reported worse knee function, lower physical activity participation and had more surgeries (128 surgeries, including 109 ACL-reconstructions) compared with participants with other acute knee injuries (six surgeries).ConclusionAcute knee injuries, including ACL injuries, affected self-reported knee function and physical activity participation for at least 6 months after index injury. More research is needed to understand how best to help people with acute knee injuries return to physical activity and achieve satisfactory knee function.

3-D Model of Proton Exchange Membrane Fuel Cells

2000 ◽  
Author(s):  
Tianhong Zhou ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Pem Fuel Cell ◽  
Proton Exchange ◽  
Three Dimensional Model ◽  
Chemical Reaction Kinetics ◽  
Fuel Cell Performance ◽  
D Model

Abstract A comprehensive three-dimensional model for a proton exchanger membrane (PEM) fuel cell is developed to evaluate the effects of various design and operating parameters on fuel cell performance. The geometrical model includes two distinct flow channels separated by the membrane and electrode assembly (MEA). This model is developed by coupling the governing equations for reactant mass transport and chemical reaction kinetics. To facilitate the numerical solution, the full PEM fuel cell was divided into three coupled domains according to the flow characteristics. The 3-D model has been applied to study species transport, heat transfer, and current density distributions within a fuel cell. The predicated polarization behavior is shown to compare well with experimental data from the literature. The modeling results demonstrate good potential for this computational model to be used in operation simulation as well as design optimization.

scholarly journals Data assimilation for volcanic ash plumes using a satellite observational operator: a case study on the 2010 Eyjafjallajökull volcanic eruption

2017 ◽  
Vol 17 (2) ◽  
pp. 1187-1205 ◽  
Author(s):  
Guangliang Fu ◽  
Fred Prata ◽  
Hai Xiang Lin ◽  
Arnold Heemink ◽  
Arjo Segers ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Volcanic Ash ◽  
Three Dimensional ◽  
Forecast Accuracy ◽  
Improve Model ◽  
Powerful Approach ◽  
Using Data ◽  
D Model

Abstract. Using data assimilation (DA) to improve model forecast accuracy is a powerful approach that requires available observations. Infrared satellite measurements of volcanic ash mass loadings are often used as input observations for the assimilation scheme. However, because these primary satellite-retrieved data are often two-dimensional (2-D) and the ash plume is usually vertically located in a narrow band, directly assimilating the 2-D ash mass loadings in a three-dimensional (3-D) volcanic ash model (with an integral observational operator) can usually introduce large artificial/spurious vertical correlations.In this study, we look at an approach to avoid the artificial vertical correlations by not involving the integral operator. By integrating available data of ash mass loadings and cloud top heights, as well as data-based assumptions on thickness, we propose a satellite observational operator (SOO) that translates satellite-retrieved 2-D volcanic ash mass loadings to 3-D concentrations. The 3-D SOO makes the analysis step of assimilation comparable in the 3-D model space.Ensemble-based DA is used to assimilate the extracted measurements of ash concentrations. The results show that satellite DA with SOO can improve the estimate of volcanic ash state and the forecast. Comparison with both satellite-retrieved data and aircraft in situ measurements shows that the effective duration of the improved volcanic ash forecasts for the distal part of the Eyjafjallajökull volcano is about 6 h.

Modelling the dynamics of a minimal protocell container

2005 ◽  
Vol 4 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Martin Nilsson Jacobi ◽  
Steen Rasmussen ◽  
Kolbjørn Tunstrøm
Keyword(s):  
Self Assembly ◽  
Large Scale ◽  
Lattice Gas ◽  
Three Dimensional ◽  
Initial Distribution ◽  
Energy Potential ◽  
Time Dynamics ◽  
Amphiphilic Molecules ◽  
Head Groups ◽  
Simplifying Assumptions

This paper is a discussion on how reaction kinetics and three-dimensional (3D) lattice simulations can be used to elucidate the dynamical properties of micelles as a possible minimal protocell container. We start with a general discussion on the role of molecular self-assembly in prebiotic and contemporary biological systems. A simple reaction kinetic model of a micellation process of amphiphilic molecules in water is then presented and solved analytically. Amphiphilic molecules are polymers with hydrophobic (water-fearing), e.g. hydrocarbon tail groups, and hydrophilic (water-loving) head groups, e.g. fatty acids. By making a few simplifying assumptions an analytical expression for the size distribution of the resulting micelles can be derived. The main part of the paper presents and discusses a lattice gas technique for a more detailed 3D simulation of molecular self-assembly of amphiphilic polymers in aqueous environments. Water molecules, hydrocarbon tail groups and hydrophilic head groups are explicitly represented on a three-dimensional discrete lattice. Molecules move on the lattice proportional to their continuous momentum. Collision rules preserve momentum and kinetic energy. Potential energy from molecular interactions are also included explicitly. The non-trivial thermodynamics of large-scale and long-time dynamics are studied. In this paper we specifically demonstrate how, from a random initial distribution, micelles are formed and grow until they destabilize and can divide. Eventually a steady state of growing and dividing micelles is formed. Towards the end of the paper we discuss the relevance of the presented results to the design of a minimal artificial protocell.

scholarly journals Quadriceps Activation Following Knee Injuries: A Systematic Review

2010 ◽  
Vol 45 (1) ◽  
pp. 87-97 ◽  
Author(s):  
Joseph M. Hart ◽  
Brian Pietrosimone ◽  
Jay Hertel ◽  
Christopher D. Ingersoll
Keyword(s):  
Anterior Cruciate Ligament ◽  
Knee Injury ◽  
Data Extraction ◽  
Cruciate Ligament ◽  
Knee Injuries ◽  
Quadriceps Muscle ◽  
Control Group ◽  
Data Sets ◽  
Weighted Mean ◽  
Anterior Cruciate

Abstract Context: Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery. Objective: To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury. Data Sources: Web of Science database. Study Selection: Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP). Data Extraction: Means, measures of variability, and prevalence of quadriceps activation (QA) failure (&lt;95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3). Data Synthesis: A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients. Conclusions: Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.

Imaging of Ligamentous Structures within the Knee Includes Much More Than the ACL

2018 ◽  
Vol 31 (02) ◽  
pp. 130-140 ◽  
Author(s):  
Corrie Yablon ◽  
Kara Gaetke-Udager
Keyword(s):  
Surgical Planning ◽  
Knee Injury ◽  
Cruciate Ligament ◽  
Knee Injuries ◽  
Imaging Study ◽  
Resonance Imaging ◽  
Injury Patterns ◽  
Additional Information ◽  
Multiple Imaging ◽  
Lateral Collateral Ligaments

AbstractLigamentous structures of the knee are numerous and complex, including the anterior and posterior cruciate ligaments, medial and lateral collateral ligaments, ligaments of the posteromedial and posterolateral corners, and the anterolateral ligament. Clinical assessment after a knee injury is paramount and can direct both the clinician's choice of imaging study and the radiologist's interpretation. Imaging is crucial in that it provides additional information for diagnosis, management, and surgical planning. Multiple imaging modalities can be used in the evaluation of the knee injuries, with radiographs an important baseline study, magnetic resonance imaging as the best tool for a comprehensive assessment including cruciate ligament evaluation, and ultrasound useful in evaluating superficial structures. Knowledge of both normal and pathological appearances of ligamentous structures, as well as typical injury patterns, is useful not only for radiologists but also for clinicians who manage patients with knee pain.

Development of an Interactive Virtual 3-D Model of the Human Testis Using the Second Life Platform

2012 ◽  
pp. 153-167
Author(s):  
Douglas R. Danforth
Keyword(s):  
Second Life ◽  
Three Dimensional ◽  
Human Testis ◽  
Anatomy And Physiology ◽  
Organ Systems ◽  
Life Context ◽  
Cellular Modeling ◽  
Primary Focus ◽  
D Model ◽  
Pedagogical Approaches

One of the strengths of a virtual environment is the ability to immerse the occupant into an environment that would otherwise be impossible. The primary focus of the author’s project in Second Life is to take advantage of this opportunity to explore novel approaches to medical education. Second Life can be used to model doctor-patient interaction, clinical diagnosis skills, and three dimensional molecular and cellular modeling of objects from individual molecules to whole organ systems, both healthy and diseased. Using the powerful building and scripting tools of the Second Life platform, the author has created a model of the human testis that students can fly through and interact with to understand how the anatomy and physiology of the testis work together to regulate sperm production. The anatomical and physiological interactions occurring during these processes are described in accompanying audio and text. The development of educational tools within the Second Life context is in its infancy. As the technology matures, the opportunities for education within Second Life will continue to expand as an important adjunct to traditional pedagogical approaches.

scholarly journals Performance and applicability of a 2.5-D ice-flow model in the vicinity of a dome

2016 ◽  
Vol 9 (7) ◽  
pp. 2301-2313 ◽  
Author(s):  
Olivier Passalacqua ◽  
Olivier Gagliardini ◽  
Frédéric Parrenin ◽  
Joe Todd ◽  
Fabien Gillet-Chaulet ◽  
...  
Keyword(s):  
Flow Model ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Observation Data ◽  
Flow Tube ◽  
Ice Flow ◽  
Linear Temperature ◽  
Ice Surface ◽  
Scanning Window ◽  
D Model

Abstract. Three-dimensional ice flow modelling requires a large number of computing resources and observation data, such that 2-D simulations are often preferable. However, when there is significant lateral divergence, this must be accounted for (2.5-D models), and a flow tube is considered (volume between two horizontal flowlines). In the absence of velocity observations, this flow tube can be derived assuming that the flowlines follow the steepest slope of the surface, under a few flow assumptions. This method typically consists of scanning a digital elevation model (DEM) with a moving window and computing the curvature at the centre of this window. The ability of the 2.5-D models to account properly for a 3-D state of strain and stress has not clearly been established, nor their sensitivity to the size of the scanning window and to the geometry of the ice surface, for example in the cases of sharp ridges. Here, we study the applicability of a 2.5-D ice flow model around a dome, typical of the East Antarctic plateau conditions. A twin experiment is carried out, comparing 3-D and 2.5-D computed velocities, on three dome geometries, for several scanning windows and thermal conditions. The chosen scanning window used to evaluate the ice surface curvature should be comparable to the typical radius of this curvature. For isothermal ice, the error made by the 2.5-D model is in the range 0–10 % for weakly diverging flows, but is 2 or 3 times higher for highly diverging flows and could lead to a non-physical ice surface at the dome. For non-isothermal ice, assuming a linear temperature profile, the presence of a sharp ridge makes the 2.5-D velocity field unrealistic. In such cases, the basal ice is warmer and more easily laterally strained than the upper one, the walls of the flow tube are not vertical, and the assumptions of the 2.5-D model are no longer valid.

Sign in / Sign up

Export Citation Format

Share Document