scholarly journals Optimal leap angle of legged and legless insects in a landscape of uniformly distributed random obstacles

2021 ◽  
Vol 8 (5) ◽  
pp. 202279
Author(s):  
Fabio Giavazzi ◽  
Samuele Spini ◽  
Marina Carpineti ◽  
Alberto Vailati
Keyword(s):  
Numerical Calculation ◽  
Maximum Probability ◽  
Air Drag ◽  
Ballistic Motion ◽  
Unknown Environments ◽  
Wide Range ◽  
Maximum Range

We investigate theoretically the ballistic motion of small legged insects and legless larvae after a jump. Notwithstanding their completely different morphologies and jumping strategies, some legged and legless animals have convergently evolved to jump with a take-off angle of 60°, which differs significantly from the leap angle of 45° that allows reaching maximum range. We show that in the presence of uniformly distributed random obstacles the probability of a successful jump is directly proportional to the area under the trajectory. In the presence of negligible air drag, the probability is maximized by a take-off angle of 60°. The numerical calculation of the trajectories shows that they are significantly affected by air drag, but the maximum probability of a successful jump still occurs for a take-off angle of 59–60° in a wide range of the dimensionless Reynolds and Froude numbers that control the process. We discuss the implications of our results for the exploration of unknown environments such as planets and disaster scenarios by using jumping robots.

scholarly journals A Spectral Method for Two-Dimensional Ocean Acoustic Propagation

2021 ◽  
Vol 9 (8) ◽  
pp. 892
Author(s):  
Xian Ma ◽  
Yongxian Wang ◽  
Xiaoqian Zhu ◽  
Wei Liu ◽  
Qiang Lan ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Spectral Method ◽  
Collocation Method ◽  
Approximation Error ◽  
Sound Field ◽  
Acoustic Propagation ◽  
Two Dimensional ◽  
Chebyshev Collocation Method ◽  
Chebyshev Collocation ◽  
Wide Range

The accurate calculation of the sound field is one of the most concerning issues in hydroacoustics. The one-dimensional spectral method has been used to correctly solve simplified underwater acoustic propagation models, but it is difficult to solve actual ocean acoustic fields using this model due to its application conditions and approximation error. Therefore, it is necessary to develop a direct solution method for the two-dimensional Helmholtz equation of ocean acoustic propagation without using simplified models. Here, two commonly used spectral methods, Chebyshev–Galerkin and Chebyshev–collocation, are used to correctly solve the two-dimensional Helmholtz model equation. Since Chebyshev–collocation does not require harsh boundary conditions for the equation, it is then used to solve ocean acoustic propagation. The numerical calculation results are compared with analytical solutions to verify the correctness of the method. Compared with the mature Kraken program, the Chebyshev–collocation method exhibits higher numerical calculation accuracy. Therefore, the Chebyshev–collocation method can be used to directly solve the representative two-dimensional ocean acoustic propagation equation. Because there are no model constraints, the Chebyshev–collocation method has a wide range of applications and provides results with high accuracy, which is of great significance in the calculation of realistic ocean sound fields.

scholarly journals Optimal Lévy-flight foraging in a finite landscape

2015 ◽  
Vol 12 (104) ◽  
pp. 20141158 ◽  
Author(s):  
Kun Zhao ◽  
Raja Jurdak ◽  
Jiajun Liu ◽  
David Westcott ◽  
Branislav Kusy ◽  
...  
Keyword(s):  
Power Law ◽  
Animal Movement ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Foraging Efficiency ◽  
Lévy Flight ◽  
Step Size ◽  
Levy Flight ◽  
Ballistic Motion ◽  
Wide Range

We present a simple model to study Lévy-flight foraging with a power-law step-size distribution in a finite landscape with countable targets. We find that different optimal foraging strategies characterized by a wide range of power-law exponent μ opt , from ballistic motion ( μ opt → 1) to Lévy flight (1 < μ opt < 3) to Brownian motion ( μ opt ≥ 3), may arise in adaptation to the interplay between the termination of foraging, which is regulated by the number of foraging steps, and the environmental context of the landscape, namely the landscape size and number of targets. We further demonstrate that stochastic returning can be another significant factor that affects the foraging efficiency and optimality of foraging strategy. Our study provides a new perspective on Lévy-flight foraging, opens new avenues for investigating the interaction between foraging dynamics and the environment and offers a realistic framework for analysing animal movement patterns from empirical data.

Centrifugal Manometer

1959 ◽  
Vol 81 (3) ◽  
pp. 341-348
Author(s):  
J. F. Kemp
Keyword(s):  
High Sensitivity ◽  
Working Fluid ◽  
Quick Response ◽  
Laboratory Conditions ◽  
Wide Range ◽  
Maximum Range ◽  
Normal Laboratory

The operating principles and mechanical construction of a micromanometer, which utilizes air in lieu of a liquid as working fluid, are described. Some of the noteworthy features of the instrument include its high sensitivity and accuracy, quick response, wide range, and ease of manipulation. Differential pressures of the order of 5 × 10−3 mm water gage can be measured with an error of 1 per cent under normal laboratory conditions. The maximum range of the prototype described is 25 mm water gage, and the corresponding error at this value amounts to about 0.25 per cent.

Fuel effects on range versus payload for modern jet aircraft

2011 ◽  
Vol 115 (1172) ◽  
pp. 627-634 ◽  
Author(s):  
S. Blakey ◽  
C. W. Wilson ◽  
M. Farmery ◽  
R. Midgley
Keyword(s):  
Specific Energy ◽  
Hydrocarbon Fuels ◽  
Fuel Properties ◽  
Maximum Payload ◽  
Wide Range ◽  
Maximum Range ◽  
Fuel Effects

Abstract With changes in the availability and quality of existing aviation fuels anticipated in the next 30 years it is timely to assess how changes in fuel properties would affect the range payload performance of aircraft. The effects on range and payload of a wide range of candidate fuels for aviation are investigated, including changes to the blends of conventional hydrocarbon fuels. Lighter fuels tend to be more desirable for commercial flights, where the flight is as close to the maximum payload as possible. Flights favouring range over payload are better suited by a more dense fuel. The hydrocarbon blends suggest for each aircraft, an optimum fuel may exist for the maximum payload and allowing the maximum range. Specific flight plans below the maximum range of the aircraft may be met with a lower specific energy fuel.

Genetic variability and divergence studies in cluster bean(Cyamopsis tetragonoloba L.) under hill zone of Karnataka, India

2016 ◽  
Author(s):  
Revati . Goudar ◽  
V. . Srinivasa ◽  
D. . Lakshmana
Keyword(s):  
Cyamopsis Tetragonoloba ◽  
Broad Sense Heritability ◽  
Genetic Advance ◽  
Number Of Clusters ◽  
Cluster Bean ◽  
Pod Yield ◽  
Wide Range ◽  
Maximum Range ◽  
Cluster Distance ◽  
High Heritability

Eighteen genotypes of cluster bean [Cyamopsis tetragonoloba (L.) Taub] were evaluated to estimate variability, broad sense heritability, genetic advance over mean and diversity for vegetable pod yield and related attributes, during summer 2014-15. Maximum range of variability was observed for number of vegetable pods per plant, number of clusters per plant and pod yield. High heritability coupled with high genetic gain in percentage was observed for number of pods per plant, number of clusters per plant, pod yield and days to first flowering. The maximum intra cluster distance was observed in cluster I and intercluster distance was high between cluster I and cluster III, this indicated wide range of variability among clusters. The per cent contribution towards genetic diversity was high for dry pod yield per plant (29.41%) followed by number of dry pods per plant (24.18%) and seed yield per plant (16.99 %).

scholarly journals Competencies and training needs and its impact on determining the professional skills of Algerian elite coaches

2019 ◽  
Vol 8 (3) ◽  
pp. 51-61
Author(s):  
Adel BELKADI ◽  
Abdelkader Benchehida ◽  
Otmane Benbernou ◽  
Mohamed Sebbane
Keyword(s):  
Education And Training ◽  
Training Needs ◽  
Academic Education ◽  
Training Experience ◽  
Maximum Probability ◽  
Professional Skills ◽  
Wide Range ◽  
Training Of Trainers ◽  
And Training

The main purpose of this study is to develop an understanding of the trainers' perceptions of competency and training needs related to professional skills in accordance with professional experience and academic education. The sample included 76 judo trainers who answered a questionnaire that included a measure that focused on the perceptions of competency and another on training needs. An exploratory factor analysis was used with the maximum probability factor (Oblimin) to determine emerging factors. A comparison of the Coaches ' concepts was made in the training experience and the academic background of the Coaches, where multiple comparisons were applied using ANOVA and Tukey. Three main areas of skills were done: skills related to annual planning; skills related to practice and competition; and personal education and training skills. Coach es' perceptions of their expertise were affected, with low-level trainers classifying themselves at lower levels of efficiency and more training needs; and higher-education Coaches in physical education were more efficient than mid-level trainers. Finally, most trainers consider them as efficient as they have indicated the training needs to be provided, which brings important feedback to the education of trainers. This suggests that trainers are an increasing their knowledge and competence in a wide range of areas that should be considered in future training of trainers programs, also to ensure the quality of education and training in the different level of physical and sports education institutes of the Algerian universities.

Analytical approach using KS elements to near-Earth orbit predictions including drag

1991 ◽  
Vol 433 (1887) ◽  
pp. 121-130 ◽  
Keyword(s):  
State Vector ◽  
Major Axis ◽  
Present Theory ◽  
Earth Satellite ◽  
The State ◽  
Satellite Orbits ◽  
Semi Major Axis ◽  
Air Drag ◽  
Orbital Parameters ◽  
Wide Range

A new analytical theory for the motion of near-Earth satellite orbits with the air drag effect is developed in terms of the KS elements, utilizing an analytical oblate exponential atmospheric density model. Due to the symmetry of the KS element equations, only one of the eight equations is integrated analytically to obtain the state vector at the end of each revolution. This is a uniqueness of the present theory. The series expansions include up to quadratic terms in e (eccentricity) and c (a small parameter dependent on the flattening of the atmosphere). Numerical studies are done with six test cases, selected to cover a wide range of eccentricity and semi-major axis, and a comparison of the three orbital parameters: semi-major axis, eccentricity and argument of perigee perturbed by the air drag with oblate atmosphere is made up to 100 revolutions with the numerically integrated values. The comparison is quite satisfactory. After 100 revolutions, with a ballistic coefficient of 50, a maximum difference of 39 metres is found in the semi-major axis comparison for a very small eccentricity (0.001) case having an initial perigee height of 391.425 km. One important advantage of the present theory is that it is singularity free, a problem faced by the analytical theories developed from the Lagrange’s planetary equations. Another advantage is that the state vector is known after each revolution.

Diffraction Control Methods of Extended Products’ Diameter

2019 ◽  
Vol 942 ◽  
pp. 97-109
Author(s):  
Evgeny Fedorov ◽  
Nataliya Chicherina ◽  
Josef Tlusty ◽  
Valeriya Tuzikova
Keyword(s):  
Large Diameter ◽  
Diffraction Method ◽  
Optical Devices ◽  
Outer Diameter ◽  
Control Zone ◽  
Technological Control ◽  
Central Maximum ◽  
Wide Range ◽  
Maximum Range ◽  
Effect Of Light

In this paper the measurement methods for extended objects’ geometry on the basis of effect of light diffraction which can be applied to technological control of products with wide range of diameters from the smallest to the largest are described. During measurement the method that allows to minimize the influence of disturbing factors on the results of measurements of diameter of thin fibers of small diameters of micron is described. Disturbing factors include excessive flare of area of the central maximum range. The diffraction method is considered that allows to increase to units of micrometers the resolution of the optical measuring converters used in devices to perform technological control of cylindrical extended products of a large diameter such as: cables, wires, cords, etc. The transformation function allowing to calculate diameter of cylindrical products irrespective of their location in a control zone on the basis of the diffraction method of delimitation of the product shadow in optical two-coordinate converters with the dispersing laser bunch is offered and experimentally confirmed. The achieved results can be used for development of high-precision optical devices of technological control of outer diameter and eccentricity of products for cable, pipe and other products in different industry fields.

scholarly journals Accuracy Problems of Numerical Calculation of Fractional Order Derivatives and Integrals Applying the Riemann-Liouville/Caputo Formulas

2016 ◽  
Vol 1 (1) ◽  
pp. 23-44 ◽  
Author(s):  
Dariusz W. Brzeziński
Keyword(s):  
Numerical Calculation ◽  
Numerical Method ◽  
Numerical Integration ◽  
Fractional Order ◽  
High Accuracy ◽  
Accuracy Improvement ◽  
Applied Method ◽  
Wide Range ◽  
Accuracy Increase ◽  
Actual Accuracy

AbstractIn the paper there are presented and evaluated for effectiveness three methods of accuracy increase of fractional order derivatives and integrals computations for application with the Riemann-Liouville/Caputo formulas. They are based on the ideas of either transforming difficult integrand in the formulas to high-accuracy computations requirements of a applied method of numerical integration or adapting a numerical method of integration to handle with high-accuracy a difficult feature in the integrand. Additional accuracy gain is obtained by incorporating increased precision into computations. The actual accuracy improvement by applying presented methods is compared with the capabilities of wide range of available methods of integration.

Design of a Multijunction Antenna Unit for EAST Lower Hybrid Current Drive

2010 ◽  
Author(s):  
Hua Jia ◽  
Fukun Liu ◽  
Jun Li ◽  
Mao Wang
Keyword(s):  
Numerical Calculation ◽  
Design Method ◽  
Current Drive ◽  
Tokamak Plasma ◽  
Lower Hybrid ◽  
Matched Load ◽  
Plasma Parameters ◽  
High Frequency Structure Simulator ◽  
Wide Range ◽  
Lower Hybrid Current Drive

A multijunction antenna unit has been designed and will be used to fabricate the new 4.6GHz Lower Hybrid Current Drive (LHCD) launcher for the long pulse operation of the Experimental Advanced Superconducting Tokamak (EAST). In this paper, the construction and design method of the multijunction antenna unit are described, and then the reflection coefficients of the unit with the matched load and with the plasma load are analyzed and discussed respectively by using High Frequency Structure Simulator (HFSS) code and by using numerical calculation based on linear coupling theory. The simulation result shows that the return loss of the antenna unit keeps below −25dB in a bandwidth of 100MHz and the power is distributed equally in the secondary waveguides of the unit. Numerical calculation result also shows that the unit has good coupling property in a wide range of tokamak plasma parameters.

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