scholarly journals Computation of Ice Shedding Trajectories Using Cartesian Grids, Penalization, and Level Sets

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Héloïse Beaugendre ◽  
François Morency ◽  
Federico Gallizio ◽  
Sophie Laurens
Keyword(s):  
Boundary Conditions ◽  
Level Sets ◽  
The Body ◽  
Cartesian Grids ◽  
Falling Sphere ◽  
Proposed Model ◽  
Efficient Alternative ◽  
Ice Shedding ◽  
Set Up ◽  
Free Falling

We propose to model ice shedding trajectories by an innovative paradigm that is based on cartesian grids, penalization and level sets. The use of cartesian grids bypasses the meshing issue, and penalization is an efficient alternative to explicitly impose boundary conditions so that the body-fitted meshes can be avoided, making multifluid/multiphysics flows easy to set up and simulate. Level sets describe the geometry in a nonparametric way so that geometrical and topological changes due to physics and in particular shed ice pieces are straight forward to follow. The model results are verified against the case of a free falling sphere. The capabilities of the proposed model are demonstrated on ice trajectories calculations for flow around iced cylinder and airfoil.

scholarly journals Prediction of Pest Insect Appearance Using Sensors and Machine Learning

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4846
Author(s):  
Dušan Marković ◽  
Dejan Vujičić ◽  
Snežana Tanasković ◽  
Borislav Đorđević ◽  
Siniša Ranđić ◽  
...  
Keyword(s):  
Machine Learning ◽  
Relative Humidity ◽  
Weather Conditions ◽  
Daily Basis ◽  
Machine Learning Algorithms ◽  
Lower Percentage ◽  
Timely Manner ◽  
Proposed Model ◽  
Set Up ◽  
Accuracy Of Prediction

The appearance of pest insects can lead to a loss in yield if farmers do not respond in a timely manner to suppress their spread. Occurrences and numbers of insects can be monitored through insect traps, which include their permanent touring and checking of their condition. Another more efficient way is to set up sensor devices with a camera at the traps that will photograph the traps and forward the images to the Internet, where the pest insect’s appearance will be predicted by image analysis. Weather conditions, temperature and relative humidity are the parameters that affect the appearance of some pests, such as Helicoverpa armigera. This paper presents a model of machine learning that can predict the appearance of insects during a season on a daily basis, taking into account the air temperature and relative humidity. Several machine learning algorithms for classification were applied and their accuracy for the prediction of insect occurrence was presented (up to 76.5%). Since the data used for testing were given in chronological order according to the days when the measurement was performed, the existing model was expanded to take into account the periods of three and five days. The extended method showed better accuracy of prediction and a lower percentage of false detections. In the case of a period of five days, the accuracy of the affected detections was 86.3%, while the percentage of false detections was 11%. The proposed model of machine learning can help farmers to detect the occurrence of pests and save the time and resources needed to check the fields.

scholarly journals A Doppler Range Compensation for Step-Frequency Continuous-Wave Radar for Detecting Small UAV

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1331
Author(s):  
Massimiliano Pieraccini ◽  
Lapo Miccinesi ◽  
Neda Rojhani
Keyword(s):  
Short Range ◽  
Continuous Wave ◽  
Range Shift ◽  
Specific Method ◽  
Step Frequency ◽  
Wave Radar ◽  
Small Uav ◽  
The Doppler Effect ◽  
Set Up ◽  
Free Falling

Step-frequency continuous-wave (SFCW) modulation can have a role in the detection of small unmanned aerial vehicles (UAV) at short range (less than 1–2 km). In this paper, the theory of SFCW range detection is reviewed, and a specific method for correcting the possible range shift due to the Doppler effect is devised. The proposed method was tested in a controlled experimental set-up, where a free-falling target (i.e., a corner reflector) was correctly detected by an SFCW radar. This method was finally applied in field for short-range detection of a small UAV.

scholarly journals A Two Joint Neck Model to Identify Malposition of the Head Relative to the Thorax

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3297
Author(s):  
Philipp M. Schmid ◽  
Christoph M. Bauer ◽  
Markus J. Ernst ◽  
Bettina Sommer ◽  
Lars Lünenburger ◽  
...  
Keyword(s):  
Neck Pain ◽  
Body Height ◽  
Biomechanical Model ◽  
The Body ◽  
Head Orientation ◽  
Neck Length ◽  
Proposed Model ◽  
Biofeedback System ◽  
Simple Measurement ◽  
The Impact

Neck pain is a frequent health complaint. Prolonged protracted malpositions of the head are associated with neck pain and headaches and could be prevented using biofeedback systems. A practical biofeedback system to detect malpositions should be realized with a simple measurement setup. To achieve this, a simple biomechanical model representing head orientation and translation relative to the thorax is introduced. To identify the parameters of this model, anthropometric data were acquired from eight healthy volunteers. In this work we determine (i) the accuracy of the proposed model when the neck length is known, (ii) the dependency of the neck length on the body height, and (iii) the impact of a wrong neck length on the models accuracy. The resulting model is able to describe the motion of the head with a maximum uncertainty of 5 mm only. To achieve this high accuracy the effective neck length must be known a priory. If however, this parameter is assumed to be a linear function of the palpable neck length, the measurement error increases. Still, the resulting accuracy can be sufficient to identify and monitor a protracted malposition of the head relative to the thorax.

Boundaries Influence on the Flow Field Around an Oscillating Sphere

2013 ◽  
Author(s):  
Domenica Mirauda ◽  
Antonio Volpe Plantamura ◽  
Stefano Malavasi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Boundary Conditions ◽  
Damping Ratio ◽  
Water Channel ◽  
Open Water ◽  
Free Surface Flows ◽  
The Body ◽  
Sphere Diameter ◽  
Oscillating Sphere

This work analyzes the effects of the interaction between an oscillating sphere and free surface flows through the reconstruction of the flow field around the body and the analysis of the displacements. The experiments were performed in an open water channel, where the sphere had three different boundary conditions in respect to the flow, defined as h* (the ratio between the distance of the sphere upper surface from the free surface and the sphere diameter). A quasi-symmetric condition at h* = 2, with the sphere equally distant from the free surface and the channel bottom, and two conditions of asymmetric bounded flow, one with the sphere located at a distance of 0.003m from the bottom at h* = 3.97 and the other with the sphere close to the free surface at h* = 0, were considered. The sphere was free to move in two directions, streamwise (x) and transverse to the flow (y), and was characterized by values of mass ratio, m* = 1.34 (ratio between the system mass and the displaced fluid mass), and damping ratio, ζ = 0.004. The comparison between the results of the analyzed boundary conditions has shown the strong influence of the free surface on the evolution of the vortex structures downstream the obstacle.

Numerical Solution of a Hydrofoil Moving Near an Interface

1996 ◽  
Vol 40 (04) ◽  
pp. 269-277
Author(s):  
G. X. Wu ◽  
T. Miloh ◽  
G. Zilman
Keyword(s):  
Boundary Conditions ◽  
Numerical Solution ◽  
Body Surface ◽  
Iteration Scheme ◽  
The Body ◽  
Two Fluids ◽  
Linearized Theory

The problem of a hydrofoil moving near an interface of two fluids of different densities is analyzed. An iteration scheme is proposed which imposes the boundary conditions on the body surface and on the interface alternately. The numerical solution is obtained by using the linearized theory and a Glauert-type expansion for the vortex distribution. Results are provided for various cases with different densities and different speeds.

Wall Effects On the Flow Dynamics of a Rigid Sphere in Motion

2021 ◽  
Author(s):  
Zhi-gang Feng ◽  
Jason Gatewood ◽  
E.E. Michaelides
Keyword(s):  
Hydrodynamic Force ◽  
Rotational Velocity ◽  
Analytical Data ◽  
Particle Diameter ◽  
Immersed Boundary ◽  
Rigid Sphere ◽  
Wall Effects ◽  
Falling Sphere ◽  
Dimensionless Ratio ◽  
Free Falling

Abstract The presence of a wall near a rigid sphere in motion is known to disturb the particle fore and aft flow field symmetry and to affect the hydrodynamic force. An Immersed Boundary Direct Numerical Simulation (IB-DNS) is used in this study to determine the wall effects on the dynamics of a free-falling sphere and the drag of a sphere moving at a constant velocity. The numerical results are validated by comparison to the published experimental, numerical, and analytical data. The pressure and velocity fields are numerically computed when the particle is in the vicinity of the wall; the transverse (lift) and longitudinal (drag) parts of the hydrodynamic force are calculated; its rotational velocity is also investigated in the case of a free-falling sphere. The flow asymmetry also causes the particle to rotate. The wall effect is shown to be significant when the dimensionless ratio of the wall distance to the particle diameter, L/D, is less than 3. The wall effects are more pronounced and when the particle Reynolds number, Re, is less than 10. Based on the computational results, a useful correlation for the wall effects on the drag coefficients spheres is derived in the range 0.75 < L/D < 3 and 0.18 < Re < 10.

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

The use of open government data to citizen empowerment: an empirical validation of a proposed model

foresight ◽  
2018 ◽  
Vol 20 (6) ◽  
pp. 665-680 ◽  
Author(s):  
Md Nahin Hossain ◽  
Md Shamim Talukder ◽  
Md Rakibul Hoque ◽  
Yukun Bao
Keyword(s):  
The Body ◽  
Open Government ◽  
Equation Modeling ◽  
Research Model ◽  
Content Type ◽  
Proposed Model ◽  
Open Government Data ◽  
Citizen Empowerment ◽  
Government Data ◽  
The Impact

Purpose The purpose of this paper is to measure the impact of open government data (OGD) on citizen empowerment. Design/methodology/approach This study advances the body of knowledge on OGD by proposing an integrated research model based on transparency, accountability, participation and collaboration dimensions. The research model was empirically tested using 275 responses using the on-paper survey from the university students and professionals in Bangladesh. Data were analyzed using the structured equation modeling technique. Findings Findings revealed that transparency and participation have a positive and significant direct and indirect influence on citizen empowerment through accountability and collaboration. Overall, the four basic pillars of OGD such as transparency, participation, accountability and collaboration interrelated with each other and have the impact on citizen empowerment. Research limitations/implications This study has proposed an instrument that sums the dimensions of open government, which avoids tautology and redundancy among OGD dimensions. More research should be done to validate the proposed model and the instruments used in this study. Practical implications For the researchers, this study provides a basis for further refinement of individual models of empowerment. For practitioners, understanding the key constructs is crucial to design, refine and implement OGD systems and applications that empower citizens, create public values and strengthen the democratic process. Originality/value This research is the first step that empirically investigates the impact of OGD on citizen empowerment which is the ultimate goals of any democratic government.

On one-dimensional unsteady flow at infinite Mach number

1968 ◽  
Vol 304 (1478) ◽  
pp. 255-273 ◽  
Keyword(s):  
Asymptotic Expansion ◽  
Blast Wave ◽  
Outer Part ◽  
The Body ◽  
Viscous Boundary Layer ◽  
Outer Flow ◽  
Hypersonic Speeds ◽  
Set Up ◽  
Viscous Boundary ◽  
Infinite Set

The use of the blast-wave analogy, as an aid to the interpretation of experimental data on the motion of a fluid past an obstacle at hypersonic speeds, has led to the theoretical study of its role in an asymptotic expansion of the solution to the governing equations at large distances downstream of the body. In all attempts to set up such an expansion it has proved necessary to divide the flow régime into two parts, an outer part dominated by the blast wave and an inner part consisting of streamlines which, originally, pass close by the body. The matching of these two regions is apparently only possible if a certain integral vanishes. In the present paper a numerical integration, in one particular set of circumstances, is carried out to test the validity of the asymptotic expansion proposed. Formally, an unsteady problem is tackled, for ease of computation, but the steady analogue follows immediately and is of exactly the form discussed in the earlier investigations. It is found that the main results are in line with the theory and that the integral in question is indistinguishable from zero. However, a deeper investigation of the asymptotic expansion shows that, for an expansion of the type envisaged, an infinite set of integrals must each vanish. The next integral does not appear to be zero according to our computations but this result is not believed to be conclusive. Assuming that all the integrals do vanish, then it appears that the inner layer, which although inviscid, has many of the characteristics of a viscous boundary layer, has the addi­tional, surprising property that it can exert no direct influence on the outer flow at large distances downstream of the body.

Feeder Bus Timetable Design and Vehicle Size Setting in Peak Hour Demand Conditions

2019 ◽  
Vol 2673 (10) ◽  
pp. 321-332 ◽  
Author(s):  
Xueping Dou ◽  
Qiang Meng
Keyword(s):  
Mixed Integer ◽  
Arrival Times ◽  
Non Linear Programming ◽  
Bee Colony ◽  
Proposed Model ◽  
Feeder Bus ◽  
Minlp Model ◽  
Failure Cost ◽  
Set Up ◽  
The Given

This study proposes a solution to the feeder bus timetabling problem, in which the terminal departure times and vehicle sizes are simultaneously determined based on the given transfer passengers and their arrival times at a bus terminal. The problem is formulated as a mixed integer non-linear programming (MINLP) model with the objective of minimizing the transfer waiting time of served passengers, the transfer failure cost of non-served passengers, and the operating costs of bus companies. In addition to train passengers who plan to transfer to buses, local passengers who intend to board buses are considered and treated as passengers from virtual trains in the proposed model. Passenger attitudes and behaviors toward the waiting queue caused by bus capacity constraints in peak hour demand conditions are explicitly embedded in the MINLP model. A hybrid artificial bee colony (ABC) algorithm is developed to solve the MINLP model. Various experiments are set up to account for the performance of the proposed model and solution algorithm.

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