scholarly journals Discrete Mechanical Growth Model for Plant Tissue

2018 ◽  
Author(s):  
Louis D. Weise ◽  
Kirsten H. W. J. ten Tusscher
Keyword(s):  
Plant Development ◽  
Material Properties ◽  
Multilevel Models ◽  
Equations Of Motion ◽  
Strain Fields ◽  
Regulatory Processes ◽  
Threshold Length ◽  
Gene Regulatory ◽  
And Control ◽  
Bulk Tissue

AbstractWe present a discrete mechanical model to study plant development. The method is built up of mass points, springs and hinges mimicking the plant cell wall’s microstructure. To model plastic growth the resting lengths of springs are adjusted; when springs exceed a threshold length, new mass points, springs and hinges, are added. We formulate a stiffness tensor for the springs and hinges as a function of the fourth rank tensor of elasticity and the geometry of the mesh. This allows us to approximate the material law as a generalized orthotropic Hooke’s law, and control material properties during growth. The material properties of the model are illustrated in numerical simulations for finite strain and plastic growth. To solve the equations of motion of mass points we assume elastostatics and use Verlet integration. The method is demonstrated in simulations when anisotropic growth causes emergent residual strain fields in cell walls and a bending of bulk tissue. The method can be used in multilevel models to study plant development, for example by coupling it to models for cytoskeletal, hormonal and gene regulatory processes.

scholarly journals Closed-form time derivatives of the equations of motion of rigid body systems

2021 ◽  
Author(s):  
Andreas Müller ◽  
Shivesh Kumar
Keyword(s):  
Rigid Body ◽  
Closed Form ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Alternative Formulation ◽  
Dynamics Of Rigid Body ◽  
Control Forces ◽  
And Control ◽  
Derivatives Of ◽  
Insight Into

AbstractDerivatives of equations of motion (EOM) describing the dynamics of rigid body systems are becoming increasingly relevant for the robotics community and find many applications in design and control of robotic systems. Controlling robots, and multibody systems comprising elastic components in particular, not only requires smooth trajectories but also the time derivatives of the control forces/torques, hence of the EOM. This paper presents the time derivatives of the EOM in closed form up to second-order as an alternative formulation to the existing recursive algorithms for this purpose, which provides a direct insight into the structure of the derivatives. The Lie group formulation for rigid body systems is used giving rise to very compact and easily parameterized equations.

scholarly journals Modeling a Knuckle-Boom Crane Control to Reduce Pendulum Motion Using the Moving Frame Method

2019 ◽  
Author(s):  
Maren Eriksen Eia ◽  
Elise Mari Vigre ◽  
Thorstein Ravneberg Rykkje
Keyword(s):  
Equations Of Motion ◽  
Moving Frame ◽  
Web Pages ◽  
Moving Frames ◽  
Pendulum Motion ◽  
Moving Frame Method ◽  
Frame Method ◽  
The Masses ◽  
And Control ◽  
Boom Crane

Abstract A Knuckle Boom Crane is a pedestal-mounted, slew-bearing crane with a joint in the middle of the distal arm; i.e. boom. This distal boom articulates at the ‘knuckle (i.e.: joint)’ and that allows it to fold back like a finger. This is an ideal configuration for a crane on a ship where storage space is a premium. This project researches the motion and control of a ship mounted knuckle boom crane to minimize the pendulum motion of a hanging load. To do this, the project leverages the Moving Frame Method (MFM). The MFM draws upon Lie group theory — SO(3) and SE(3) — and Cartan’s Moving Frames. This, together with a compact notation from geometrical physics, makes it possible to extract the equations of motion, expeditiously. The work reported here accounts for the masses and geometry of all components, interactive motor couples and prepares for buoyancy forces and added mass on the ship. The equations of motion are solved numerically using a 4th order Runge Kutta (RK4), while solving for the rotation matrix for the ship using the Cayley-Hamilton theorem and Rodriguez’s formula for each timestep. This work displays the motion on 3D web pages, viewable on mobile devices.

scholarly journals A framework for identifying and promoting metacognitive knowledge and control in online discussants

2009 ◽  
Vol 34 (2) ◽  
Author(s):  
Elizabeth Murphy
Keyword(s):  
Computer Mediated Communication ◽  
Online Discussions ◽  
Mediated Communication ◽  
Computer Based Learning ◽  
Regulatory Processes ◽  
Computer Mediated ◽  
Computer Based ◽  
Metacognitive Activity ◽  
And Control ◽  
Source Of Information

The effectiveness of computer-based learning environments depends on learners’ deployment of metacognitive and self-regulatory processes. Analysis of transmitted messages in a context of Computer Mediated Communication can provide a source of information on metacognitive activity. However, existing models or frameworks (e.g., Henri, 1992) that support the identification and assessment of metacognition have been described as subjective, lacking in clear criteria, and unreliable in contexts of scoring. This paper develops a framework that might be used by researchers analysing transcripts of discussions for evidence of engagement in metacognition, by instructors assessing learners’ participation in online discussions or by designers setting up metacognitive experiences for learners. Résumé : L’efficacité des environnements d’apprentissage assistés par ordinateur repose sur l’utilisation de processus de métacognition et d’autorégulation par les apprenants. L’analyse de messages transmis dans un contexte de communication assistée par ordinateur peut constituer une source d’information sur l’activité métacognitive. Cependant, les modèles et cadres existants (p. ex. Henri, 1992) qui permettent la reconnaissance et l’évaluation de la métacognition ont été décrits comme subjectifs, dépourvus de critères clairs et peu fiables dans des contextes de notation. Cet article décrit un cadre qui pourrait être utilisé par les chercheurs qui analysent les transcriptions de discussions à la recherche de preuves d’engagement métacognitif, par les instructeurs qui procèdent à l’évaluation de la participation des apprenants à des discussions en ligne ou par les concepteurs qui élaborent des expériences métacognitives pour les apprenants.

scholarly journals A Simulation Model for Computing the Loads Generated at Landing Site During Helicopter Take-Off or Landing Operation

2019 ◽  
Vol 2019 (2) ◽  
pp. 59-75
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Equations Of Motion ◽  
Landing Site ◽  
Simulation Method ◽  
Rigid Bodies ◽  
Landing Gear ◽  
Rotor Blades ◽  
Wind Gust ◽  
The Galerkin Method ◽  
Lumped Masses ◽  
And Control

Summary The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.

The Integrated Mission Simulator

SIMULATION ◽  
1964 ◽  
Vol 2 (2) ◽  
pp. R-9-R-23
Author(s):  
Edward E. Markson ◽  
John L. Stricker
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Landing Site ◽  
Euler Angle ◽  
Space Mission ◽  
Six Degrees Of Freedom ◽  
Guidance And Control ◽  
Manned Space ◽  
And Control ◽  
Guidance Technique

Space mission simulator programs may be divided into two broad categories: (1) training tools (quali tative devices often simulating a continuous mission), and (2) laboratory tools (quantitative devices treating the mission in phases, each phase being programmed separately to obtain optimum scaling). This paper describes the development of an analog program capable of continuously simulating an entire lunar mission in six degrees of freedom with high resolu tion throughout. The reported work logically traces the program development through the equations of motion, the guidance and control equations, and the analog mechanization. The translation equations are de veloped using a modified form of Encke's method; two reference origins are utilized at the two points of primary interest—the landing site and the target vehicle—such that the displacements are approach ing a minimum in the regions where the highest reso lution is required. The variables are rescaled as this region is approached to obtain maximum accuracy. Relays, stepping switches and diode gates are used for rescaling and to re-reference origins. A particular Euler angle sequence is selected based on matrix validity criteria applied to the mission. A previously reported guidance technique is shown to be appli cable to all phases of the mission. It is concluded that the method demonstrated in this paper leads to minimum computer loading for simulating a manned space mission without program discontinuities. Supporting data include an analog- computed trajectory representative of a long-dura tion mission, which is compared in detail with a digital solution.

scholarly journals Correction: Bistability versus Bimodal Distributions in Gene Regulatory Processes from Population Balance

2011 ◽  
Vol 7 (10) ◽  
Author(s):  
Che-Chi Shu ◽  
Anushree Chatterjee ◽  
Gary Dunny ◽  
Wei-Shou Hu ◽  
Doraiswami Ramkrishna
Keyword(s):  
Population Balance ◽  
Regulatory Processes ◽  
Gene Regulatory

Effects of Hull and Control Surface Roughness on Ship Maneuvering

2020 ◽  
pp. 1-10
Author(s):  
John C. Daidola
Keyword(s):  
Surface Roughness ◽  
Equations Of Motion ◽  
Control Surface ◽  
Ship Maneuvering ◽  
Single Screw ◽  
Operation And Maintenance ◽  
Hydrodynamic Derivatives ◽  
Turning Maneuver ◽  
And Control ◽  
Surface Vessel

The effects of hull roughness on ship maneuvering characteristics are investigated. The hydrodynamic derivatives in the equations of motion for surface vessel maneuvering are modified to incorporate roughness of the hull and rudder. Vessel lifetime roughness profiles are postulated based on construction, coatings, operation, and maintenance for a vessel life of 25 years. These are then applied to the turning maneuver for single screw cargo ships with block coefficients from .60 to .80. The implications for naval missions are discussed.

scholarly journals Trust motivation: The self-regulatory processes underlying trust decisions

2019 ◽  
Vol 9 (2-3) ◽  
pp. 99-123 ◽  
Author(s):  
Lisa van der Werff ◽  
Alison Legood ◽  
Finian Buckley ◽  
Antoinette Weibel ◽  
David de Cremer
Keyword(s):  
Goal Setting ◽  
Feedback Loop ◽  
Future Research ◽  
Two Phase ◽  
Cognitive Trust ◽  
Regulatory Processes ◽  
Dynamic View ◽  
Definition Of ◽  
And Behavior ◽  
And Control

Theorizing about trust has focused predominantly on cognitive trust cues such as trustworthiness, portraying the trustor as a relatively passive observer reacting to the attributes of the other party. Using self-determination and control theories of motivation, we propose a model of trust motivation that explores the intraindividual processes involved in the volitional aspects of trust decision-making implied by the definition of trust as a willingness to be vulnerable. We distinguish between intrinsic and extrinsic drivers of trust and propose a two-phase model of trust goal setting and trust regulation. Our model offers a dynamic view of the trusting process and a framework for understanding how trust cognition, affect and behavior interact over time. Furthermore, we discuss how trust goals may be altered or abandoned via a feedback loop during the trust regulation process. We conclude with a discussion of potential implications for existing theory and future research.

scholarly journals Experimental Parasite Infection Causes Genome-Wide Changes in DNA Methylation

2020 ◽  
Vol 37 (8) ◽  
pp. 2287-2299 ◽  
Author(s):  
Kostas Sagonas ◽  
Britta S Meyer ◽  
Joshka Kaufmann ◽  
Tobias L Lenz ◽  
Robert Häsler ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Infected Fish ◽  
Parasite Infection ◽  
Control Fish ◽  
Regulatory Processes ◽  
Neuropeptide Ff ◽  
Genome Wide ◽  
Parasite Infections ◽  
And Shifts ◽  
And Control

Abstract Parasites are arguably among the strongest drivers of natural selection, constraining hosts to evolve resistance and tolerance mechanisms. Although, the genetic basis of adaptation to parasite infection has been widely studied, little is known about how epigenetic changes contribute to parasite resistance and eventually, adaptation. Here, we investigated the role of host DNA methylation modifications to respond to parasite infections. In a controlled infection experiment, we used the three-spined stickleback fish, a model species for host–parasite studies, and their nematode parasite Camallanus lacustris. We showed that the levels of DNA methylation are higher in infected fish. Results furthermore suggest correlations between DNA methylation and shifts in key fitness and immune traits between infected and control fish, including respiratory burst and functional trans-generational traits such as the concentration of motile sperm. We revealed that genes associated with metabolic, developmental, and regulatory processes (cell death and apoptosis) were differentially methylated between infected and control fish. Interestingly, genes such as the neuropeptide FF receptor 2 and the integrin alpha 1 as well as molecular pathways including the Th1 and Th2 cell differentiation were hypermethylated in infected fish, suggesting parasite-mediated repression mechanisms of immune responses. Altogether, we demonstrate that parasite infection contributes to genome-wide DNA methylation modifications. Our study brings novel insights into the evolution of vertebrate immunity and suggests that epigenetic mechanisms are complementary to genetic responses against parasite-mediated selection.

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