scholarly journals Turbulent wake past a three-dimensional blunt body. Part 1. Global modes and bi-stability

2013 ◽  
Vol 722 ◽  
pp. 51-84 ◽  
Author(s):  
M. Grandemange ◽  
M. Gohlke ◽  
O. Cadot
Keyword(s):  
Time Scales ◽  
Three Dimensional ◽  
Body Part ◽  
The Body ◽  
Recirculation Region ◽  
Stream Velocity ◽  
Lateral Direction ◽  
Reduction Strategies ◽  
Long Time ◽  
The Impact

AbstractThe flow around the three-dimensional blunt geometry presented in the work of Ahmed, Ramm & Faitin (Tech. Rep., 1984) is investigated experimentally at $\mathit{Re}= {U}_{0} H/ \nu = 9. 2\times 1{0}^{4} $ (where ${U}_{0} $ is free-stream velocity, $H$ the height of the body and $\nu $ viscosity). The very large recirculation on the base responsible for the dominant part of the drag is characterized. The analyses of the coherent dynamics of the wake reveal the presence of two very distinctive time scales. At long time scales ${T}_{l} \sim 1{0}^{3} H/ {U}_{0} $, the recirculation region shifts between two preferred reflectional-symmetry-breaking positions leading to a statistically symmetric wake; the sequence of these asymmetric states is random. This bi-stable behaviour is independent of the Reynolds number but occurs only above a critical value of ground clearance. At short time scales ${T}_{s} \sim 5H/ {U}_{0} $, the wake presents weak coherent oscillations in the vertical and lateral directions. They are respectively associated with the interaction of the top/bottom and lateral shear layers; when normalized by the height and width of the body, the Strouhal numbers are close to 0.17. These results suggest an alternate shedding associated with the vertical oscillation and a one-sided vortex shedding in the lateral direction with an orientation linked to the current asymmetric position. Finally, the impact of these coherent wake motions on the base pressure is discussed to motivate further drag reduction strategies.

Maximizing Recall of Gruesome Images for Health Effects Advertising: An Experimental Investigation

2010 ◽  
Vol 16 (4) ◽  
pp. 112-121 ◽  
Author(s):  
Brennen W. Mills ◽  
Owen B. J. Carter ◽  
Robert J. Donovan
Keyword(s):  
Experimental Investigation ◽  
Body Part ◽  
The Body ◽  
Advertising Effectiveness ◽  
Body Parts ◽  
Online Study ◽  
Video Clips ◽  
Video Images ◽  
The Impact

The objective of this case study was to experimentally manipulate the impact on arousal and recall of two characteristics frequently occurring in gruesome depictions of body parts in smoking cessation advertisements: the presence or absence of an external physical insult to the body part depicted; whether or not the image contains a clear figure/ground demarcation. Three hundred participants (46% male, 54% female; mean age 27.3 years, SD = 11.4) participated in a two-stage online study wherein they viewed and responded to a series of gruesome 4-s video images. Seventy-two video clips were created to provide a sample of images across the two conditions: physical insult versus no insult and clear figure/ground demarcation versus merged or no clear figure/ground demarcation. In stage one, participants viewed a randomly ordered series of 36 video clips and rated how “confronting” they considered each to be. Seven days later (stage two), to test recall of each video image, participants viewed all 72 clips and were asked to identify those they had seen previously. Images containing a physical insult were consistently rated more confronting and were remembered more accurately than images with no physical insult. Images with a clear figure/ground demarcation were rated as no more confronting but were consistently recalled with greater accuracy than those with unclear figure/ground demarcation. Makers of gruesome health warning television advertisements should incorporate some form of physical insult and use a clear figure/ground demarcation to maximize image recall and subsequent potential advertising effectiveness.

A Liberating Experience. On Becoming a Work of Art

2020 ◽  
Vol 7 (2) ◽  
pp. 411-430
Author(s):  
Maja Tabea Jerrentrup
Keyword(s):  
Three Dimensional ◽  
The Body ◽  
The Other ◽  
Work Of Art ◽  
Other Hand ◽  
Film Clips ◽  
Long Time ◽  
The One ◽  
Body Painting ◽  
Dimensional Surface

Abstract The art of bodypainting that is fairly unknown to a wider public turns the body into a canvas - it is a frequently used phrase in the field of bodypainting that illustrates the challenge it faces: it uses a three-dimensional surface and has to cope with its irregularities, but also with the model’s abilities and characteristics. This paper looks at individuals who are turned into art by bodypainting. Although body painting can be very challenging for them - they have to expose their bodies and to stand still for a long time while getting transformed - models report that they enjoy both the process and the result, even if they are not confident about their own bodies. Among the reasons there are physical aspects like the sensual enjoyment, but also the feeling of being part of something artistic. This is enhanced and preserved through double staging - becoming a threedimentional work of art and then being staged for photography or film clips. This process gives the model the chance to experience their own body in a detached way. On the one hand, bodypainting closely relates to the body and on the other hand, it can help to over-come the body.

scholarly journals Flow-induced vibrations of a rotating cylinder in an arbitrary direction

2018 ◽  
Vol 860 ◽  
pp. 739-766 ◽  
Author(s):  
Rémi Bourguet
Keyword(s):  
Three Dimensional ◽  
Rotating Cylinder ◽  
The Body ◽  
Arbitrary Direction ◽  
Fast Rotation ◽  
Flow Past ◽  
Symmetrical Configuration ◽  
Wide Range ◽  
Flow Induced Vibrations ◽  
The Impact

The flow-induced vibrations of an elastically mounted circular cylinder, free to oscillate in an arbitrary direction and forced to rotate about its axis, are examined via two- and three-dimensional simulations, at a Reynolds number equal to 100, based on the body diameter and inflow velocity. The behaviour of the flow–structure system is investigated over the entire range of vibration directions, defined by the angle $\unicode[STIX]{x1D703}$ between the direction of the current and the direction of motion, a wide range of values of the reduced velocity $U^{\star }$ (inverse of the oscillator natural frequency) and three values of the rotation rate (ratio between the cylinder surface and inflow velocities), $\unicode[STIX]{x1D6FC}\in \{0,1,3\}$, in order to cover the reference non-rotating cylinder case, as well as typical slow and fast rotation cases. The oscillations of the non-rotating cylinder ($\unicode[STIX]{x1D6FC}=0$) develop under wake-body synchronization or lock-in, and their amplitude exhibits a bell-shaped evolution, typical of vortex-induced vibrations (VIV), as a function of $U^{\star }$. When $\unicode[STIX]{x1D703}$ is increased from $0^{\circ }$ to $90^{\circ }$ (or decreased from $180^{\circ }$ to $90^{\circ }$), the bell-shaped curve tends to monotonically increase in width and magnitude. For all angles, the flow past the non-rotating body is two-dimensional with formation of two counter-rotating spanwise vortices per cycle. The behaviour of the system remains globally the same for $\unicode[STIX]{x1D6FC}=1$. The principal effects of the slow rotation are a slight amplification of the VIV-like responses and widening of the vibration windows, as well as a limited asymmetry of the responses and forces about the symmetrical configuration $\unicode[STIX]{x1D703}=90^{\circ }$. The impact of the fast rotation ($\unicode[STIX]{x1D6FC}=3$) is more pronounced: VIV-like responses persist over a range of $\unicode[STIX]{x1D703}$ but, outside this range, the system is found to undergo a transition towards galloping-like oscillations characterised by amplitudes growing unboundedly with $U^{\star }$. A quasi-steady modelling of fluid forcing predicts the emergence of galloping-like responses as $\unicode[STIX]{x1D703}$ is varied, which suggests that they could be mainly driven by the mean flow. It, however, appears that flow unsteadiness and body motion remain synchronised in this vibration regime where a variety of multi-vortex wake patterns are uncovered. The interaction with flow dynamics results in deviations from the quasi-steady prediction. The successive steps in the evolution of the vibration amplitude versus $U^{\star }$, linked to wake pattern switch, are not captured by the quasi-steady approach. The flow past the rapidly-rotating, vibrating cylinder becomes three-dimensional over an interval of $\unicode[STIX]{x1D703}$ including the in-line oscillation configuration, with only a minor effect on the system behaviour.

scholarly journals CNN with Pose Segmentation for Suspicious Object Detection in MMW Security Images

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4974 ◽  
Author(s):  
Zhichao Meng ◽  
Man Zhang ◽  
Hongxian Wang
Keyword(s):  
Object Recognition ◽  
Object Detection ◽  
Binary Classification ◽  
Three Dimensional ◽  
Recognition Task ◽  
Body Part ◽  
The Body ◽  
Deep Cnn ◽  
Human Pose ◽  
Weak Shape

Millimeter-wave (MMW) imaging scanners can see through clothing to form a three-dimensional holographic image of the human body and suspicious objects, providing a harmless alternative for non-contacting searches in security check. Suspicious object detection in MMW images is challenging, since most of them are small, reflection-weak, shape, and reflection-diverse. Conventional detectors with artificial neural networks, like convolution neural network (CNN), usually take the problem of finding suspicious objects as an object recognition task, yielding difficulties in developing large-amount and complete sample sets of objects. In this paper, a new algorithm is developed using the human pose segmentation followed by the deep CNN detection. The algorithm is emphasized to learn the similarity with humans’ body clutter applied to training corresponding CNNs after the image segmentation base of the pose estimation. Moreover, the suspicious object recognition in the MMW image is converted to a binary classification task. Instead of recognizing all sorts of suspicious objects, the CNN detector determines whether the body part images present the abnormal patterns containing suspicious objects. The proposed algorithm that is based on CNN with the pose segmentation has concise configuration, but optimal performance in the suspicious object detection. Extensive experiments confirm the effectiveness and superiority of the proposal.

Semantics of Hawrami Body Part Terms

2012 ◽  
Vol 16 (3) ◽  
pp. 319-335
Author(s):  
Bistoon Abasi ◽  
Amer Gheitury
Keyword(s):  
Native Speakers ◽  
Body Part ◽  
Field Work ◽  
The Body ◽  
Body Parts ◽  
Human Beings ◽  
Long Time ◽  
Semantic Properties ◽  
Different Levels ◽  
Internal Body

Human body as a universal possession of human beings constitutes an interesting domain where questions regarding semantic categorisations might be sought crosslinguistically. In the following, we will attempt to describe the terms used to refer to the body in Hawrami, an Iranian language spoken in Paveh, a small township in the western province of Kermanshah near Iraqi borders. Due to the scarcity of written material, the inventory of 202 terms referring to external and internal body parts were obtained through a field work, which took a long time, and techniques, such as the “colouring task”, observation and recording the terms as used in ordinary conversations and informal interviews with native speakers. The semantic properties of the terms and the way they are related in a partonymy or locative relationship were also investigated. As far as universals of body part terms are concerned, while conforming to ‘depth principle’ concerning the number of levels each partonomy may consist of, Hawrami violates an important feature of this principle by not allowing transitive relations between different levels of partonomic hierarchies. In addition, Hawrami lacks a term for labelling the ‘whole’.

A Study of Impacts of Coupled Model Initial Shocks and State–Parameter Optimization on Climate Predictions Using a Simple Pycnocline Prediction Model

2011 ◽  
Vol 24 (23) ◽  
pp. 6210-6226 ◽  
Author(s):  
S. Zhang
Keyword(s):  
Time Scales ◽  
Parameter Optimization ◽  
Time Scale ◽  
Model Simulation ◽  
Coupled Model ◽  
State Parameter ◽  
Model Parameters ◽  
Forecast Errors ◽  
Long Time ◽  
The Impact

Abstract A skillful decadal prediction that foretells varying regional climate conditions over seasonal–interannual to multidecadal time scales is of societal significance. However, predictions initialized from the climate-observing system tend to drift away from observed states toward the imperfect model climate because of the model biases arising from imperfect model equations, numeric schemes, and physical parameterizations, as well as the errors in the values of model parameters. Here, a simple coupled model that simulates the fundamental features of the real climate system and a “twin” experiment framework are designed to study the impact of initialization and parameter optimization on decadal predictions. One model simulation is treated as “truth” and sampled to produce “observations” that are assimilated into other simulations to produce observation-estimated states and parameters. The degree to which the model forecasts based on different estimates recover the truth is an assessment of the impact of coupled initial shocks and parameter optimization on climate predictions of interests. The results show that the coupled model initialization through coupled data assimilation in which all coupled model components are coherently adjusted by observations minimizes the initial coupling shocks that reduce the forecast errors on seasonal–interannual time scales. Model parameter optimization with observations effectively mitigates the model bias, thus constraining the model drift in long time-scale predictions. The coupled model state–parameter optimization greatly enhances the model predictability. While valid “atmospheric” forecasts are extended 5 times, the decadal predictability of the “deep ocean” is almost doubled. The coherence of optimized model parameters and states is critical to improve the long time-scale predictions.

Assessing the atmosphere-surface exchange of gaseous elemental mercury using passive air samplers

2020 ◽  
Author(s):  
Meng Si ◽  
Michelle Feigis ◽  
Isabel Quant ◽  
Shreya Mistry ◽  
Melanie Snow ◽  
...  
Keyword(s):  
Time Scales ◽  
Forest Canopy ◽  
Elemental Mercury ◽  
Permafrost Degradation ◽  
Concentration Gradients ◽  
Surface Exchange ◽  
Gaseous Elemental Mercury ◽  
The Earth ◽  
Long Time ◽  
The Impact

<p>The specific properties of gaseous elemental mercury (GEM) allow it to undergo bidirectional exchange between the atmosphere and the Earth’s surface. Determining the direction and the magnitude of GEM’s atmosphere-surface flux is possible and has been accomplished using micrometeorological and chamber techniques, but (i) is complex and labor-intensive, and (ii) often only yields fluxes over relatively short time scales. A recently developed passive air sampler for GEM has the precision required for identifying and quantifying vertical concentration gradients above the Earth’s surface. The feasibility and performance of this approach is currently being tested in a number of field studies aimed at the: (i) measurement of GEM concentration gradients above both mercury-contaminated and background forest soils, (ii) quantification of vertical concentration gradients on a tower through a temperate deciduous forest canopy, and (iii) measurement of mercury concentration gradients over stable and thawing permafrost to determine the effect of permafrost degradation on GEM evasion. Contrasting with earlier flux studies, these investigations cover long time periods (up to 1.5 years) and have coarse temporal resolution (monthly to seasonally). Significant gradients of GEM air concentrations, both increasing and decreasing with height above ground, were observed, implying that at a minimum, the method is able to identify the flux direction of GEM. Under the right circumstances, this method can also be used to estimate the approximate magnitude of the GEM air-surface exchange flux. The measured gradients also reveal the impact of factors such as temperature, solar irradiance, and snow cover on air-surface exchange. The method holds promise for establishing the direction and size of exchange fluxes at long time scales of months to a year, especially in study areas where access, effort and cost are prohibitive to longer duration studies with existing approaches.</p>

scholarly journals The impact of pelvic lateral rotation on hindlimb kinematics and stride length in the red-legged running frog, Kassina maculata

2019 ◽  
Vol 6 (5) ◽  
pp. 190060 ◽  
Author(s):  
Amber J. Collings ◽  
Laura B. Porro ◽  
Cameron Hill ◽  
Christopher T. Richards
Keyword(s):  
High Speed ◽  
Stride Length ◽  
Reference Frames ◽  
Comparative Anatomy ◽  
Three Dimensional ◽  
Video Data ◽  
The Body ◽  
Kinematic Models ◽  
Lateral Rotation ◽  
The Impact

Some frog species, such as Kassina maculata (red-legged running frog), use an asynchronous walking/running gait as their primary locomotor mode. Prior comparative anatomy work has suggested that lateral rotation of the pelvis improves walking performance by increasing hindlimb stride length; however, this hypothesis has never been tested. Using non-invasive methods, experimental high-speed video data collected from eight animals were used to create two three-dimensional kinematic models. These models, each fixed to alternative local anatomical reference frames, were used to investigate the hypothesis that lateral rotation of the mobile ilio-sacral joint in the anuran pelvis plays a propulsive role in walking locomotion by increasing hindlimb stride length. All frogs used a walking gait (duty factor greater than 0.5) despite travelling over a range of speeds (0.04–0.23 m s −1 ). The hindlimb joint motions throughout a single stride were temporally synchronized with lateral rotation of the pelvis. The pelvis itself, on average, underwent an angular excursion of 12.71° (±4.39°) with respect to the body midline during lateral rotation. However, comparison between our two kinematic models demonstrated that lateral rotation of the pelvis only increases the cranio-caudal excursion of the hindlimb modestly. Thus, we propose that pelvic lateral rotation is not a stride length augmenting mechanism in K. maculata .

A Three-Dimensional Model of Droplet Impinging, Solidification and Suspension on the Substrate

2011 ◽  
Vol 346 ◽  
pp. 222-227
Author(s):  
Sheng Zhu ◽  
Feng Liang Yin ◽  
Jian Liu ◽  
Yuan Yuan Liang
Keyword(s):  
Surface Tension ◽  
Manufacturing Process ◽  
Three Dimensional ◽  
Metal Droplet ◽  
The Body ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
High Impact Velocity ◽  
The Impact ◽  
First Time

A three-dimensional model was built to study a molten metal droplet impact on an edge of the substrate in droplet deposition manufacturing process for the first time. The whole calculation domain, including the substrate, was described using same fluid conservation equations, which is to say that the remolding and solidification of substrate was considered also. Droplet free surface was tracked by volume-of-fluid (VOF) algorithm. The effect of surface tension on the droplet was taken into consideration by means of considering surface tension to be a component of the body force. The simulated results show that the droplet in liquid phase can keep suspending on the substrate at a role of surface tension. A too high impact velocity would make parts of droplet splash away the substrate which is not allowed in manufacturing process. The offset between edge of droplet and side edge of substrate influences dramatically the impact of the droplet.

Three-Dimensional Modeling and Simulation of a Falling Electronic Device

2006 ◽  
Vol 2 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Hua Shan ◽  
Jianzhong Su ◽  
Jiansen Zhu ◽  
Leon Xu
Keyword(s):  
Rigid Body ◽  
Electronic Device ◽  
Impact Load ◽  
Three Dimensional ◽  
The Body ◽  
Contact Dynamics ◽  
Model Verification ◽  
Multiple Impacts ◽  
Element Analysis ◽  
The Impact

This article focuses on a realistic mathematical model for multiple impacts of a rigid body to a viscoelastic ground and its comparison to theoretic results. The methodology is used to study impact on an electronic device. When an electronic device drops to the floor at an uneven level, the rapid successions of impact sequence are important for their shock response to internal structure of the devices. A three-dimensional, continuous contact, computational impact model has been developed to simulate a sequence of multiple impacts of a falling rigid body with the ground. The model simulates the impact procedure explicitly and thus is capable of providing detailed information regarding impact load, impact contact surface, and the status of the body during the impact. For the purposes of model verification, we demonstrate the numerical simulation of a falling rod problem, in which the numerical results are in good agreement with the analytic solutions based on discrete contact dynamics impact models. It is indicated by the numerical experiments that simultaneous impacts occurred to multiple locations of the body and that subsequent impacts might be larger than initial ones due to different angles of impact. The differential equation-based computational model is shown to be realistic and efficient in simulating impact sequence and laid a foundation for detailed finite element analysis of the interior impact response of an electronic device.

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