Indirect estimates of wing-propulsion forces in horizontally diving Atlantic puffins (Fratercula arctica L.)

2003 ◽  
Vol 81 (5) ◽  
pp. 816-822 ◽  
Author(s):  
L Christoffer Johansson
Keyword(s):  
Drag Coefficient ◽  
Video Sequence ◽  
Sagittal Plane ◽  
Force Production ◽  
The Body ◽  
Fratercula Arctica ◽  
Body Drag ◽  
Reduced Frequency ◽  
Hydrodynamic Mechanism ◽  
Propulsive Mechanism

Instantaneous force production in wing-propelled diving Atlantic puffins (Fratercula arctica) was investigated using four birds for which instantaneous estimates of velocity and acceleration of the body were made. The quasi-steady resultant force acting on the body in the sagittal plane was calculated using acceleration reaction coefficients, buoyancy estimates, and drag coefficients taken from the literature and calculated, using two different methods, from a video sequence of a puffin gliding (CDw = 0.021 and 0.026, respectively). The forces calculated from the motion of the body coincide well with the wing-beat cycle, with a forward- and upward-directed force produced by the wings during the downstroke and a forward- and downward-directed force produced during the upstroke. The result suggests that a thrust force may also be produced during at least the lower-stroke reversal. This means either that there may exist some undescribed propulsive mechanism, possibly caused by an interaction of the wings beneath the body, or that the body drag coefficient may be overestimated. However, the body drag coefficient calculated in the study is close to the coefficients measured on dead birds. Furthermore, I conclude that the high reduced frequency (average 0.82) suggests a non-steady-state hydrodynamic mechanism of wing-propelled diving in puffins.

scholarly journals An exploration of strategies used by dressage horses to control moments around the center of mass when performing passage

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3866 ◽  
Author(s):  
Hilary M. Clayton ◽  
Sarah Jane Hobbs
Keyword(s):  
Sagittal Plane ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Force Production ◽  
The Body ◽  
Camera Motion ◽  
Slow Speed ◽  
Moment Arms ◽  
Trunk Posture ◽  
The Moment

BackgroundLocomotion results from the generation of ground reaction forces (GRF) that cause translations of the center of mass (COM) and generate moments that rotate the body around the COM. The trot is a diagonally-synchronized gait performed by horses at intermediate locomotor speeds. Passage is a variant of the trot performed by highly-trained dressage horses. It is distinguished from trot by having a slow speed of progression combined with great animation of the limbs in the swing phase. The slow speed of passage challenges the horse’s ability to control the sagittal-plane moments around the COM. Footfall patterns and peak GRF are known to differ between passage and trot, but their effects on balance management, which we define here as the ability to control nose-up/nose-down pitching moments around the horse’s COM to maintain a state of equilibrium, are not known. The objective was to investigate which biomechanical variables influence pitching moments around the COM in passage.MethodsThree highly-trained dressage horses were captured by a 10-camera motion analysis system (120 Hz) as they were ridden in passage over four force platforms (960 Hz). A full-body marker set was used to track the horse’s COM and measure balance variables including total body center of pressure (COP), pitching moments, diagonal dissociation timing, peak force production, limb protraction–retraction, and trunk posture. A total of twenty passage steps were extracted and partial correlation (accounting for horse) was used to investigate significant (P < 0.05) relationships between variables.ResultsHindlimb mean protraction–retraction correlated significantly with peak hindlimb propulsive forces (R = 0.821;P < 0.01), mean pitching moments (R = 0.546,P = 0.016), trunk range of motion, COM craniocaudal location and diagonal dissociation time (P < 0.05).DiscussionPitching moments around the COM were controlled by a combination of kinematic and kinetic adjustments that involve coordinated changes in GRF magnitudes, GRF distribution between the diagonal limb pairs, and the moment arms of the vertical GRFs. The moment arms depend on hoof placements relative to the COM, which were adjusted by changing limb protraction–retraction angles. Nose-up pitching moments could also be increased by providing a larger hindlimb propulsive GRF.

Field estimates of body drag coefficient on the basis of dives in passerine birds

2001 ◽  
Vol 204 (6) ◽  
pp. 1167-1175 ◽  
Author(s):  
A. Hedenstrom ◽  
F. Liechti
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Western Mediterranean ◽  
Important Variable ◽  
The Body ◽  
Flight Mechanics ◽  
Dimensionless Number ◽  
Passerine Birds ◽  
Body Drag

During forward flight, a bird's body generates drag that tends to decelerate its speed. By flapping its wings, or by converting potential energy into work if gliding, the bird produces both lift and thrust to balance the pull of gravity and drag. In flight mechanics, a dimensionless number, the body drag coefficient (C(D,par)), describes the magnitude of the drag caused by the body. The drag coefficient depends on the shape (or streamlining), the surface texture of the body and the Reynolds number. It is an important variable when using flight mechanical models to estimate the potential migratory flight range and characteristic flight speeds of birds. Previous wind tunnel measurements on dead, frozen bird bodies indicated that C(D,par) is 0.4 for small birds, while large birds should have lower values of approximately 0.2. More recent studies of a few birds flying in a wind tunnel suggested that previous values probably overestimated C(D,par). We measured maximum dive speeds of passerine birds during the spring migration across the western Mediterranean. When the birds reach their top speed, the pull of gravity should balance the drag of the body (and wings), giving us an opportunity to estimate C(D,par). Our results indicate that C(D,par) decreases with increasing Reynolds number within the range 0.17-0.77, with a mean C(D,par) of 0.37 for small passerines. A somewhat lower mean value could not be excluded because diving birds may control their speed below the theoretical maximum. Our measurements therefore support the notion that 0.4 (the ‘old’ default value) is a realistic value of C(D,par) for small passerines.

Body balance in a free-standing position in road and off-road cyclists

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Paulina Hebisz ◽  
Rafal Hebisz ◽  
Marek Zaton
Keyword(s):  
Sagittal Plane ◽  
Standing Position ◽  
The Body ◽  
Free Standing ◽  
Body Balance ◽  
Eyes Closed ◽  
Road Cycling ◽  
Progressive Exercise ◽  
Before And After ◽  
Road Cyclists

AbstractBackground: The purpose of this study was to compare body balance in road and off-road cyclists, immediately before and after the racing season.Material/Methods: Twenty individuals participated in the study and they were divided into two groups: specialists in road-cycling (n = 10) and in off-road cycling (n = 10). Immediately before and after the five-month racing season stabilographic trials were carried out (at rest and after progressive exercise). In assessing body balance the distance and velocity of the centre shifts (in the anterior-posterior and left-right direction) were analysed. The tests were performed with the cyclists’ eyes open, eyes closed, and in feedback.Results: After the racing season, in the off-road cyclists’ group, distance and velocity of the centre of pressure shifts increased after a progressive exercise.Conclusions: In the off-road cyclists’ group the balance of the body in the sagittal plane deteriorated after the racing season. Moreover, after the racing season off-road cyclists were characterized by a worse balance of the body, compared to road cyclists

Correction of Posture Deviations in the Sagittal Plane Using the Pilates Method

2019 ◽  
pp. 3-13
Author(s):  
Alexandru Cîtea ◽  
George-Sebastian Iacob
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Postural Control ◽  
Human Body ◽  
Sagittal Plane ◽  
The Body ◽  
Lower Limbs ◽  
Low Back ◽  
Pilates Method ◽  
The Relationship

Posture is commonly perceived as the relationship between the segments of the human body upright. Certain parts of the body such as the cephalic extremity, neck, torso, upper and lower limbs are involved in the final posture of the body. Musculoskeletal instabilities and reduced postural control lead to the installation of nonstructural posture deviations in all 3 anatomical planes. When we talk about the sagittal plane, it was concluded that there are 4 main types of posture deviation: hyperlordotic posture, kyphotic posture, rectitude and "sway-back" posture.Pilates method has become in the last decade a much more popular formof exercise used in rehabilitation. The Pilates method is frequently prescribed to people with low back pain due to their orientation on the stabilizing muscles of the pelvis. Pilates exercise is thus theorized to help reactivate the muscles and, by doingso, increases lumbar support, reduces pain, and improves body alignment.

Spinal Balance/Alignment—Clinical Relevance and Biomechanics

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Anoli Shah ◽  
Justin V. C. Lemans ◽  
Joseph Zavatsky ◽  
Aakash Agarwal ◽  
Moyo C. Kruyt ◽  
...  
Keyword(s):  
Social Interaction ◽  
Sagittal Balance ◽  
Sagittal Plane ◽  
The Body ◽  
Optimal Configuration ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Compensatory Mechanisms ◽  
Spinal Balance ◽  
Spinal Imbalance

In the anatomy of a normal spine, due to the curvatures in various regions, the C7 plumb line (C7PL) passes through the sacrum so that the head is centered over the pelvic-ball and socket hip and ankle joints. A failure to recognize malalignment in the sagittal plane can affect the patient's activity as well as social interaction due to deficient forward gaze. The sagittal balance configuration leads to the body undertaking the least muscular activities as possible necessary to maintain spinal balance. Global sagittal imbalance is energy consuming and often results in painful compensatory mechanisms that in turn negatively influence the patient's quality of life, self-image, and social interaction due to inability to maintain a horizontal gaze. Deformity, scoliosis, kyphosis, trauma, and/or surgery are some ways that this optimal configuration can be disturbed, thus requiring higher muscular activity to maintain posture and balance. Several parameters such as the thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and hip and leg positions influence the sagittal balance and thus the optimal configuration of spinal alignment. This review examines the clinical and biomechanical aspects of spinal imbalance, and the biomechanics of spinal balance as dictated by deformities—ankylosing spondylitis (AS), scoliosis and kyphosis; surgical corrections—pedicle subtraction osteotomies (PSO), long segment stabilizations, and consequent postural complications like proximal and distal junctional kyphosis. The study of the biomechanics involved in spinal imbalance is relatively new and thus the literature is rather sparse. This review suggests several potential research topics in the area of spinal biomechanics.

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

scholarly journals Anatomical variants of pulmonary segments and uni-portal thoracoscopic segmentectomy for lung cancer in a patient with Kartagener syndrome: a case report

2021 ◽  
Author(s):  
Di Zhou ◽  
Ye Tian ◽  
Yao Lu ◽  
Xueying Yang
Keyword(s):  
Lung Cancer ◽  
Rare Variants ◽  
Sagittal Plane ◽  
Early Stage ◽  
Situs Inversus Totalis ◽  
Middle Lobe ◽  
The Body ◽  
Kartagener Syndrome ◽  
Early Stage Lung Cancer ◽  
Cancer Lesion

AbstractSitus inversus totalis (SIT) is an extremely uncommon congenital disease where the major organs of the body are transposed through the sagittal plane. Kartagener syndrome is a complication of SIT with immotility of bronchial cilia, bronchiectasis, and chronic sinusitis. There is no report describing patients with Kartagener syndrome who accept uni-portal segmentectomies for lung cancer in past studies. Here we report a 74-year-old female patient with both Kartagener syndrome and a small early-stage lung cancer lesion located in the apical segment of the left upper lobe (LS1). The pulmonary segment anatomy of the left upper lobe in this case, which had very rare variants, was presented and interpreted in detail. This patient underwent an anatomic segmentectomy to the LS1 and a partial excision to the left middle lobe with bronchiectasis through a single 3 cm length incision. We believe that the case can give surgeons some experience and inspiration.

Survey on the Indirect Methods of Potential Flow Used for the Optimization of Airships Profile

2014 ◽  
Vol 554 ◽  
pp. 717-723
Author(s):  
Reza Abbasabadi Hassanzadeh ◽  
Shahab Shariatmadari ◽  
Ali Chegeni ◽  
Seyed Alireza Ghazanfari ◽  
Mahdi Nakisa
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Field ◽  
Drag Coefficient ◽  
Body Surface ◽  
Potential Flow ◽  
The Body ◽  
Indirect Methods ◽  
Singularity Method ◽  
Singularity Distribution

The present study aims to investigate the optimized profile of the body through minimizing the Drag coefficient in certain Reynolds regime. For this purpose, effective aerodynamic computations are required to find the Drag coefficient. Then, the computations should be coupled thorough an optimization process to obtain the optimized profile. The aerodynamic computations include calculating the surrounding potential flow field of an object, calculating the laminar and turbulent boundary layer close to the object, and calculating the Drag coefficient of the object’s body surface. To optimize the profile, indirect methods are used to calculate the potential flow since the object profile is initially amorphous. In addition to the indirect methods, the present study has also used axial singularity method which is more precise and efficient compared to other methods. In this method, the body profile is not optimized directly. Instead, a sink-and-source singularity distribution is used on the axis to model the body profile and calculate the relevant viscose flow field.

scholarly journals POSTURAL PROFILE OF INDIVIDUALS WITH HAM/TSP

2013 ◽  
Vol 1 (2) ◽  
Author(s):  
Maíra Carvalho Macêdo ◽  
Abrahão Fontes Baptista ◽  
Bernardo Galvão Castro-Filho ◽  
Edelvita Fernanda Duarte ◽  
Naiane Patrício ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
The Body ◽  
Forward Displacement ◽  
Ankle Angle ◽  
Postural Assessment ◽  
De Medicina

Objectives:The aim of this survey was to delineate the profile of patients with HTLV-1 associated with HAM/TSP. Methods:This was cross-sectionalconducted at the HTLV Center of "EscolaBahiana de Medicina e SaúdePública,Bahia",Brazil,30 volunteerswith HAM / TSP werepairedwith 30 healthysubjects, whounderwent a postural evaluationbymeansof a Postural Assessment Software (SAPO®).Results:A trend characterized by postural projection of the trunk forward or backward, forward displacement of the body, bending the knees and ankle angle reduction was noted.Conclusion:This study demonstrates that there is a posture typical of the HAM/TSP patient which manifests itself with changes in the sagittal plane.

BODY DRAG, FEATHER DRAG AND INTERFERENCE DRAG OF THE MOUNTING STRUT IN A PEREGRINE FALCON,FALCO PEREGRINUS

1990 ◽  
Vol 149 (1) ◽  
pp. 449-468 ◽  
Author(s):  
VANCE A. Tucker
Keyword(s):  
The Body ◽  
Peregrine Falcon ◽  
Reference Area ◽  
Drag Coefficients ◽  
Minimum Drag ◽  
Body Drag ◽  
The Mean ◽  
The Difference ◽  
Parabuteo Unicinctus ◽  
Crosssectional Area

1. The mean, minimum drag coefficients (CD,B) of a frozen, wingless peregrine falcon body and a smooth-surfaced model of the body were 0.24 and 0.14, respectively, at air speeds between 10.0 and 14.5 ms−1. These values were measured with a drag balance in a wind tunnel, and use the maximum crosssectional area of the body as a reference area. The difference between the values indicates the effect of the feathers on body drag. Both values for CD,B a r e lower than those predicted from most other studies of avian body drag, which yield estimates of CD,B up to 0.41. 2. Several factors must be controlled to measure minimum drag on a frozen body. These include the condition of the feathers, the angle of the head and tail relative to the direction of air flow, and the interference drag generated by the drag balance and the strut on which the body is mounted. 3. This study describes techniques for measuring the interference drag generated by (a) the drag balance and mounting strut together and (b) the mounting strut alone. Corrections for interference drag may reduce the apparent body drag by more than 20%. 4. A gliding Harris' hawk (Parabuteo unicinctus), which has a body similar to that of the falcon in size and proportions, has an estimated body drag coefficient of 0.18. This value can be used to compute the profile drag coefficients of Harris' hawk wings when combined with data for this species in the adjoining paper (Tucker and Heine, 1990).

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