The Vertical Mean Force and Moment of Submerged Bodies Under Waves

1971 ◽  
Vol 15 (03) ◽  
pp. 231-245 ◽  
Author(s):  
C. M. Lee ◽  
J. N. Newman
Keyword(s):  
Free Surface ◽  
Added Mass ◽  
Cross Sectional Area ◽  
The Body ◽  
Slender Body ◽  
Longitudinal Distribution ◽  
Vertical Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Mean

A neutrally buoyant slender body of arbitrary sectional form, submerged beneath a free surface, is free to respond to an incident plane progressive wave system. The fluid is assumed inviscid, incompressible, homogeneous and infinitely deep. The first-order oscillatory motion of the body and the second-order time-average vertical force and pitching moment acting on the body are obtained in terms of Kochin's function. By use of slender-body theory for a deeply submerged body, the final expressions for the mean force and the moment are shown to depend on the longitudinal distribution of sectional area and added mass and on the amplitude and the frequency of the ambient surface waves. The magnitude of the mean force for various simple geometric cylinders is compared with that of a circular cylinder of equal cross-sectional area. The mean force on a nonaxisymmetric body is often approximated by replacing the section with circular profiles of equivalent cross-sectional area. A better scheme of approximation is presented, based on a simple way of estimating the two-dimensional added mass. It is expected that the effect of the cross-sectional geometry on mean vertical force and moment will be more significant when the body is very close to the free surface.

scholarly journals Atrophy patterns in isolated subscapularis lesions

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Gernot Seppel ◽  
Andreas Voss ◽  
Daniel J. H. Henderson ◽  
Simone Waldt ◽  
Bernhard Haller ◽  
...  
Keyword(s):  
Muscle Atrophy ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Control Group ◽  
Sectional Area ◽  
Cross Sectional ◽  
Subscapularis Muscle ◽  
Mri Scans ◽  
The Mean ◽  
The Cross

Abstract Background While supraspinatus atrophy can be described according to the system of Zanetti or Thomazeau there is still a lack of characterization of isolated subscapularis muscle atrophy. The aim of this study was to describe patterns of muscle atrophy following repair of isolated subscapularis (SSC) tendon. Methods Forty-nine control shoulder MRI scans, without rotator cuff pathology, atrophy or fatty infiltration, were prospectively evaluated and subscapularis diameters as well as cross sectional areas (complete and upper half) were assessed in a standardized oblique sagittal plane. Calculation of the ratio between the upper half of the cross sectional area (CSA) and the total CSA was performed. Eleven MRI scans of patients with subscapularis atrophy following isolated subscapularis tendon tears were analysed and cross sectional area ratio (upper half /total) determined. To guarantee reliable measurement of the CSA and its ratio, bony landmarks were also defined. All parameters were statistically compared for inter-rater reliability, reproducibility and capacity to quantify subscapularis atrophy. Results The mean age in the control group was 49.7 years (± 15.0). The mean cross sectional area (CSA) was 2367.0 mm2 (± 741.4) for the complete subscapularis muscle and 1048.2 mm2 (± 313.3) for the upper half, giving a mean ratio of 0.446 (± 0.046). In the subscapularis repair group the mean age was 56.7 years (± 9.3). With a mean cross sectional area of 1554.7 mm2 (± 419.9) for the complete and of 422.9 mm2 (± 173.6) for the upper half of the subscapularis muscle, giving a mean CSA ratio of 0.269 (± 0.065) which was seen to be significantly lower than that of the control group (p < 0.05). Conclusion Analysis of typical atrophy patterns of the subscapularis muscle demonstrates that the CSA ratio represents a reliable and reproducible assessment tool in quantifying subscapularis atrophy. We propose the classification of subscapularis atrophy as Stage I (mild atrophy) in case of reduction of the cross sectional area ratio < 0.4, Stage II (moderate atrophy) in case of < 0.35 and Stage III (severe atrophy) if < 0.3.

scholarly journals The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint

2016 ◽  
Vol 52 (1) ◽  
pp. 12-23 ◽  
Author(s):  
Ran S Sopher ◽  
Andrew A Amis ◽  
D Ceri Davies ◽  
Jonathan RT Jeffers
Keyword(s):  
Pennation Angle ◽  
Muscle Architecture ◽  
Cross Sectional Area ◽  
Contact Forces ◽  
Sectional Area ◽  
Muscle Forces ◽  
Cross Sectional ◽  
Contact Loads ◽  
The Mean ◽  
And Function

Data about a muscle’s fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep pennation angles. Inter-subject variability in muscle architecture affected ankle muscle and contact loads only slightly. The link between muscle architecture and function contributes to the understanding of the relationship between muscle structure and function.

A computed method for noninvasive MRI assessment of pulmonary arterial hypertension

2004 ◽  
Vol 96 (2) ◽  
pp. 463-468 ◽  
Author(s):  
Eric Laffon ◽  
Christophe Vallet ◽  
Virginie Bernard ◽  
Michel Montaudon ◽  
Dominique Ducassou ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Pulmonary Arterial Pressure ◽  
Cross Sectional Area ◽  
Physical Parameters ◽  
Sectional Area ◽  
Biophysical Parameters ◽  
Cross Sectional ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Arterial ◽  
The Mean

The present method enables the noninvasive assessment of mean pulmonary arterial pressure from magnetic resonance phase mapping by computing both physical and biophysical parameters. The physical parameters include the mean blood flow velocity over the cross-sectional area of the main pulmonary artery (MPA) at the systolic peak and the maximal systolic MPA cross-sectional area value, whereas the biophysical parameters are related to each patient, such as height, weight, and heart rate. These parameters have been measured in a series of 31 patients undergoing right-side heart catheterization, and the computed mean pulmonary arterial pressure value (PpaComp) has been compared with the mean pressure value obtained from catheterization (PpaCat) in each patient. A significant correlation was found that did not differ from the identity line PpaComp = PpaCat ( r = 0.92). The mean and maximal absolute differences between PpaComp and PpaCat were 5.4 and 11.9 mmHg, respectively. The method was also applied to compute the MPA systolic and diastolic pressures in the same patient series. We conclude that this computed method, which combines physical (whoever the patient) and biophysical parameters (related to each patient), improves the accuracy of MRI to noninvasively estimate pulmonary arterial pressures.

scholarly journals Patients with Achilles Tendon Rupture Have a Degenerated Contralateral Achilles Tendon: An Elastography Study

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Qianru Li ◽  
Qi Zhang ◽  
Yehua Cai ◽  
Yinghui Hua
Keyword(s):  
Achilles Tendon ◽  
Axial Strain ◽  
Achilles Tendon Rupture ◽  
Cross Sectional Area ◽  
Control Group ◽  
Computer Assisted ◽  
Study Group ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Mean

Purpose. To evaluate differences of Achilles tendon (AT) hardness and morphology between asymptomatic tendons in patients with acute AT ruptures on the contralateral side and asymptomatic tendons in healthy people by using computer-assisted quantification on axial-strain sonoelastography (ASE). Methods. The study consisted of 33 asymptomatic tendons in 33 patients (study group) and 34 tendons in 19 healthy volunteers (control group). All the tendons were examined by both ASE and conventional ultrasound. Computer-assisted quantification on ASE was applied to extract hardness variables, including the mean (Hmean), 20th percentile (H20), median (H50) and skewness (Hsk) of the hardness within tendon, and the ratio of the mean hardness within tendon to that outside tendon (Hratio) and three morphological variables: the thickness (THK), cross-sectional area, and eccentricity (ECC) of tendons. Results. The Hmean, Hsk, H20, H50, and Hratio in the proximal third of the tendon body in study group were significantly smaller than those in control group (Hmean: 0.43±0.09 vs 0.50±0.07, p=0.001; Hsk: -0.53±0.51 vs -1.09±0.51, p<0.001; H20: 0.31±0.10 vs 0.40±0.10, p=0.001; H50: 0.45±0.10 vs 0.53±0.08, p<0.001; Hratio: 1.01±0.25 vs 1.20±0.23, p=0.003). The THK and cross-sectional area of tendons in the study group were larger than those in the control group (p<0.05). Conclusions. As a quantitative objective method, the computer-assisted ASE reveals that the asymptomatic ATs contralateral to acute rupture are softer than those of healthy control group at the proximal third and the asymptomatic tendons in people with rupture history are thicker, larger, and rounder than those of normal volunteers especially at the middle and distal thirds of AT body.

scholarly journals INDIRECT DECOMPRESSION BY LATERAL FUSION: ANALYSIS OF SAGITAL ALIGNMENT

2021 ◽  
Vol 20 (1) ◽  
pp. 50-54
Author(s):  
Thyago Guirelle Silva ◽  
Rodrigo Augusto do Amaral ◽  
Raphael Rezende Pratali ◽  
Luiz Pimenta
Keyword(s):  
Magnetic Resonance ◽  
Pelvic Incidence ◽  
Magnetic Resonance Images ◽  
Cross Sectional Area ◽  
Disc Height ◽  
Lower Limbs ◽  
Sectional Area ◽  
Cross Sectional ◽  
Indirect Decompression ◽  
The Mean

ABSTRACT Objective: To verify the effectiveness of indirect decompression after lateral access fusion in patients with high pelvic incidence. Methods: A retrospective, non-comparative, non-randomized analysis of 22 patients with high pelvic incidence who underwent lateral access fusion, 11 of whom were male and 11 female, with a mean age of 63 years (52-74), was conducted. Magnetic resonance exams were performed within one year after surgery. The cross-sectional area of the thecal sac, anterior and posterior disc heights, and bilateral foramen heights, measured pre- and postoperatively in axial and sagittal magnetic resonance images, were analyzed. The sagittal alignment parameters were measured using simple radiographs. The clinical results were evaluated using the ODI and VAS (back and lower limbs) questionnaires. Results: In all cases, the technique was performed successfully without neural complications. The mean cross-sectional area increased from 126.5 mm preoperatively to 174.3 mm postoperatively. The mean anterior disc height increased from 9.4 mm preoperatively to 12.8 mm postoperatively, while the posterior disc height increased from 6.3 mm preoperatively to 8.1 mm postoperatively. The mean height of the right foramen increased from 157.3 mm in the preoperative period to 171.2 mm in the postoperative period and that of the left foramen increased from 139.3 mm in the preoperative to 158.9 mm in the postoperative. Conclusions: This technique is capable of correcting misalignment in spinal deformity, achieving fusion and promoting the decompression of neural elements. Level of evidence III; Retrospective study.

Correlation between the Minimal Cross-Sectional Area of the Nasal Cavity and Body Surface Area: Preliminary Results in Normal Patients

2002 ◽  
Vol 16 (4) ◽  
pp. 209-213 ◽  
Author(s):  
Martin Jurlina ◽  
Ranko Mladina ◽  
Krsto Dawidowsky ◽  
Davor Ivanković ◽  
Zeljko Bumber ◽  
...  
Keyword(s):  
Surface Area ◽  
Body Surface Area ◽  
Body Surface ◽  
Anterior Part ◽  
Inferior Turbinate ◽  
Objective Evaluation ◽  
Cross Sectional Area ◽  
The Body ◽  
Sectional Area ◽  
Cross Sectional

Nasal symptoms often are inconsistent with rhinoscopic findings. However, the proper diagnosis and treatment of nasal pathology requires an objective evaluation of the narrow segments of the anterior part of the nasal cavities (minimal cross-sectional area [MCSA]). The problem is that the value of MCSA is not a unique parameter for the entire population, but rather it is a distinctive value for particular subject (or smaller groups of subjects). Consequently, there is a need for MCSA values to be standardized in a simple way that facilitates the comparison of results and the selection of our treatment regimens. We examined a group of 157 healthy subjects with normal nasal function. A statistically significant correlation was found between the body surface area and MCSA at the level of the nasal isthmus and the head of the inferior turbinate. The age of subjects was not found a statistically significant predictor for the value of MCSA. The results show that the expected value of MCSA can be calculated for every subject based on anthropometric data of height and weight.

CFD Solution of a Two-Canopy Parachute in a Top-to-Top Formation With a Vent of Air From One of Its Canopy

2008 ◽  
Author(s):  
Mohammad J. Izadi
Keyword(s):  
Cross Sectional Area ◽  
The Body ◽  
The Other ◽  
Bluff Bodies ◽  
Variable Cross ◽  
Sectional Area ◽  
Cross Sectional ◽  
Drag Forces ◽  
Varied Form ◽  
Two Bodies

A CFD study of a 3 Dimensional flow field around two bodies (Two Canopies of a Parachutes) as two bluff bodies in an incompressible fluid (Air) is modeled here. Formations of these two bodies are top-to-top (One on the top of the other) with respect to the center of each other. One canopy with a constant cross sectional area with a vent of air at its apex, and the other with a variable cross sectional area with no vent is studied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple radius of the body with a vent on it. The flow condition is considered to be 3-D, unsteady, turbulent, and incompressible. The vertical distances between the bluff bodies, cross sectional area, and also vent ratio of bluff bodies are varied here. The drag forces with static pressures around the two bodies are calculated. From the numerical results, it can be seen that, the drag coefficient is constant on the range of zero to twenty percent of the vent ratio and it decreases for higher vent ratios for when the upper parachute is smaller than the lower one, and it increases for when the upper parachute is larger than the lower one. Both Steady and Unsteady cases gave similar results especially when the distance between the canopies is increased.

Treatment of Acute Focal Cerebral Ischemia with Intermittent, Low Dose Mannitol

Neurosurgery ◽  
1979 ◽  
Vol 5 (6) ◽  
pp. 687-691 ◽  
Author(s):  
John R. Little
Keyword(s):  
Low Dose ◽  
Cross Sectional Area ◽  
Cerebral Injury ◽  
Left Middle Cerebral Artery ◽  
Sodium Pentobarbital ◽  
Sectional Area ◽  
Cross Sectional ◽  
Luminal Diameter ◽  
Mca Occlusion ◽  
The Mean

Abstract The object of this investigation was to study the effects of intermittent, low dose mannitol therapy on conscious cats after acute left middle cerebral artery (MCA) occlusion. A simple implanted device was applied to the proximal left MCA of 40 adult cats using microsurgical techniques. In the acute experiments, 10 cats were untreated and 10 cats received mannitol (0.5 g/kg intravenously) immediately before occlusion and again 3, 6, and 9 hours later. They subsequently underwent intra-arterial perfusion with colloidal carbon and buffered paraformaldehyde 12 hours after occlusion. The plasma osmolality immediately before perfusion was 316 ± 2 (SD) milliosmoles in untreated cats and 331 ± 5 milliosmoles in treated cats. Gross swelling, impaired carbon filling, and breakdown of the blood-brain barrier (BBB) to fluorescein were seen in the left MCA territory of 8 untreated cats and 1 treated cat. The mean percentage of gray matter cross sectional area where severe ischemic neuronal alterations predominated was 45 ± 12% in untreated and 14 ± 16% in treated cats (p &lt; 0.01). The mean capillary luminal diameter in the left sylvian cortex was 4.5 ± 1.0 μ in untreated cats (control, 6.5 ± 1.0 μ) and 5.5 ± 1.0 μ in treated cats. In the subacute experiments, 10 cats were not treated and 10 cats received mannitol as in the acute experiments. The cats were killed with a large bolus of sodium pentobarbital 48 hours after left MCA occlusion. Gross swelling and breakdown of the BBB were less severe in treated cats. The mean cross sectional area of infarcted tissue was 55 ± 12% in untreated cats and 33 ± 21% in treated cats (p &lt; 1.0). The findings of this study indicate that intermittent, low dose mannitol therapy delays the onset of ischemic cerebral injury and may reduce the size of the eventual infarct or convert a potential infarct into a so-called “transient ischemic attack.”

scholarly journals A comparison of minimal cross sectional areas, nasal volumes and peak nasal inspiratory flow between patients with obstructive sleep apnea and healthy controls

2016 ◽  
Vol 54 (4) ◽  
pp. 342-347
Author(s):  
M.H.S. Moxness ◽  
V. Bugten ◽  
W.M. Thorstensen ◽  
S. Nordgard ◽  
G. Bruskeland
Keyword(s):  
Nasal Cavity ◽  
Inspiratory Flow ◽  
Cross Sectional Area ◽  
Healthy Controls ◽  
Sectional Area ◽  
Cavity Volume ◽  
Cross Sectional ◽  
The Mean ◽  
And Function ◽  
Peak Nasal Inspiratory Flow

Background: The differences in nasal geometry and function between OSA patients and healthy individuals are not known. Our aim was to evaluate the differences in nasal geometry and function using acoustic rhinometry (AR) and peak nasal inspiratory flow (PNIF) between an OSA population and healthy controls. Methodology: The study was designed as a prospective case-control study. Ninety-three OSA patients and 92 controls were enrolled from 2010 to 2015. The minimal cross-sectional area (MCA) and the nasal cavity volume (NCV) in two parts of the nose (MCA0-3/NCV0-3 and MCA3-5.2/NCV3-5.2) and PNIF were measured at baseline and after decongestion. Results: The mean MCA0-3 in the OSA group was 0.49 cm2; compared to 0.55 cm2 in controls. The mean NCV0-3 correspondingly was 2.51 cm3 compared to 2.73 cm3 in controls. PNIF measured 105 litres/minute in the OSA group and 117 litres/minute in the controls. Conclusions: OSA patients have a lower minimum cross-sectional area, nasal cavity volume and peak inspiratory flow compared to controls. Our study supports the view that changes in the nasal cavity may contribute to development of OSA.

scholarly journals The Effects of Hypergravity on Xenopus Embryo Growth and Cardiac Hypertrophy

2012 ◽  
Vol 11 (1 and 2) ◽  
Author(s):  
Bryce Duchman ◽  
Darrell Wiens
Keyword(s):  
Xenopus Laevis ◽  
Body Length ◽  
Cardiac Tissue ◽  
Cross Sectional Area ◽  
The Body ◽  
Sectional Area ◽  
Cross Sectional ◽  
Organism Growth ◽  
Ventricle Size ◽  
Average Body

All life on earth has developed and evolved in a unity gravity (1G) environment. Any deviation below or above 1G could affect animal development, a period when much change occurs and sensitivity is high. We imposed simulated hypergravity through centrifugation and analyzed the effects on the overall body length and cardiac growth of Xenopus laevis embryos. We predicted that increased contractile force would be required from the heart to adequately circulate blood, dispersing nutrients, and that this would inhibit organism growth and possibly induce a state of hypertrophy. Embryos reaching gastrulation stage were exposed to a 7G or 1G (control) field via centrifugation for 96 hours. We then recorded behavior, mortality and took body length measurements. We found no significant differences in behavior or mortality, however, body length was significantly reduced by an average of 6.8% in the 7G group. We then fixed, embedded, sectioned and stained embryos in order to investigate the dimensions of cardiac tissue and of the cardiac region of the body using image analysis software. We found the 7G group had a significantly reduced average body cross-sectional area (-18%) and yet a significantly larger ventricular cross-sectional area (+36%) when compared to the 1G group. The average ratio of ventricle cross-sectional area to average body cross-sectional area was significantly higher in the 7G group when compared to the 1G. From these data, we conclude that hypergravity has a significant inhibitory impact on the Xenopus laevis embryo growth and causes a significant increase in ventricle size.

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