scholarly journals Self-rotating 3D chiral mechanical metamaterials

2021 ◽  
Vol 477 (2251) ◽  
pp. 20200825
Author(s):  
K. K. Dudek ◽  
A. Drzewiński ◽  
M. Kadic
Keyword(s):  
Rotational Motion ◽  
Attitude Control ◽  
Structural Unit ◽  
Three Dimensional ◽  
Point Of View ◽  
Complex Structures ◽  
Structural Elements ◽  
Mechanical Metamaterials ◽  
Potential Applications ◽  
And Control

In this work, we demonstrate that three-dimensional chiral mechanical metamaterials are able to self-twist and control their global rotation. We also discuss the possibility of adjusting the extent of the global rotation manifested by the system in a programmable manner. In addition, we show that the effect of the global rotation can be observed both for small systems composed of a single structural unit as well as more complex structures incorporating several structural elements connected to each other. Finally, it is discussed that the results presented in this work are very promising from the point of view of potential applications such as satellites or telescopes in space, where appropriately designed mechanical metamaterials could be used for the attitude control as well as other systems where the control of the rotational motion is required.

Cyclopean Vision, Size Estimation, and Presence in Orthostereoscopic Images

2001 ◽  
Vol 10 (3) ◽  
pp. 312-330 ◽  
Author(s):  
Bernard Harper ◽  
Richard Latto
Keyword(s):  
Visual System ◽  
Three Dimensional ◽  
Point Of View ◽  
Psychophysical Experiment ◽  
Size Estimation ◽  
Human Form ◽  
Image Capture ◽  
Series Of Experiments ◽  
Abstract Shapes ◽  
And Control

Stereo scene capture and generation is an important facet of presence research in that stereoscopic images have been linked to naturalness as a component of reported presence. Three-dimensional images can be captured and presented in many ways, but it is rare that the most simple and “natural” method is used: full orthostereoscopic image capture and projection. This technique mimics as closely as possible the geometry of the human visual system and uses convergent axis stereography with the cameras separated by the human interocular distance. It simulates human viewing angles, magnification, and convergences so that the point of zero disparity in the captured scene is reproduced without disparity in the display. In a series of experiments, we have used this technique to investigate body image distortion in photographic images. Three psychophysical experiments compared size, weight, or shape estimations (perceived waist-hip ratio) in 2-D and 3-D images for the human form and real or virtual abstract shapes. In all cases, there was a relative slimming effect of binocular disparity. A well-known photographic distortion is the perspective flattening effect of telephoto lenses. A fourth psychophysical experiment using photographic portraits taken at different distances found a fattening effect with telephoto lenses and a slimming effect with wide-angle lenses. We conclude that, where possible, photographic inputs to the visual system should allow it to generate the cyclopean point of view by which we normally see the world. This is best achieved by viewing images made with full orthostereoscopic capture and display geometry. The technique can result in more-accurate estimations of object shape or size and control of ocular suppression. These are assets that have particular utility in the generation of realistic virtual environments.

scholarly journals Platonic solids generate their four-dimensional analogues

2013 ◽  
Vol 69 (6) ◽  
pp. 592-602 ◽  
Author(s):  
Pierre-Philippe Dechant
Keyword(s):  
Coxeter Groups ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Root Systems ◽  
Point Of View ◽  
Platonic Solids ◽  
Four Dimensions ◽  
Potential Applications ◽  
Regular Convex ◽  
Quasi Crystals

This paper shows how regular convex 4-polytopes – the analogues of the Platonic solids in four dimensions – can be constructed from three-dimensional considerations concerning the Platonic solids alone.Viathe Cartan–Dieudonné theorem, the reflective symmetries of the Platonic solids generate rotations. In a Clifford algebra framework, the space of spinors generating such three-dimensional rotations has a natural four-dimensional Euclidean structure. The spinors arising from the Platonic solids can thus in turn be interpreted as vertices in four-dimensional space, giving a simple construction of the four-dimensional polytopes 16-cell, 24-cell, theF4root system and the 600-cell. In particular, these polytopes have `mysterious' symmetries, that are almost trivial when seen from the three-dimensional spinorial point of view. In fact, all these induced polytopes are also known to be root systems and thus generate rank-4 Coxeter groups, which can be shown to be a general property of the spinor construction. These considerations thus also apply to other root systems such as A_{1}\oplus I_{2}(n) which induces I_{2}(n)\oplus I_{2}(n), explaining the existence of the grand antiprism and the snub 24-cell, as well as their symmetries. These results are discussed in the wider mathematical context of Arnold's trinities and the McKay correspondence. These results are thus a novel link between the geometries of three and four dimensions, with interesting potential applications on both sides of the correspondence, to real three-dimensional systems with polyhedral symmetries such as (quasi)crystals and viruses, as well as four-dimensional geometries arising for instance in Grand Unified Theories and string and M-theory.

An Oil-Hydraulic Workbench for Advanced Dynamic Testing

2006 ◽  
Author(s):  
Enrico Ravina
Keyword(s):  
Dynamic Testing ◽  
Mechanical Equipment ◽  
Structural Elements ◽  
Virtual Instrumentation ◽  
Shock Absorbers ◽  
Mechanical Field ◽  
Potential Applications ◽  
Static And Dynamic Tests ◽  
Mechanical Devices ◽  
And Control

The paper refers on a polyvalent oil-hydraulic testbench, designed and realized in order to develop a wide and diversified range of static and dynamic tests on mechanical components and structural elements. The testbench is an experimental mechatronic unit, integrating mechanical equipment, electronic devices and elaboration and control systems, aided by virtual instrumentation. In order to describe the main features and potentialities of the proposed testbench, the paper refers on tests of specific mechanical devices (shock absorbers) and of samples of structural elements (glued junctions). The possible and potential applications of the proposed workbench are very wide and oriented to validation, experimental identification, advanced testing and diagnostics in mechanical field.

scholarly journals Seeking the Finer Light

1999 ◽  
Vol 121 (05) ◽  
pp. 50-53 ◽  
Author(s):  
Michael Valenti
Keyword(s):  
Process Management ◽  
Bulk Material ◽  
Three Dimensional ◽  
Complex Structures ◽  
Laser Measurement ◽  
Construction Sites ◽  
Three Dimensional Measurement ◽  
Laser Systems ◽  
Corn Processing ◽  
And Control

Manufacturers, engineers, architects, and researchers are using the precision, speed, and noncontact processes and achieve more control. Riegl Laser Systems of Horn, Austria, designed its 3-D LMS-Z210 imaging scanner to generate 240,000 laser measurement points within 30 seconds to create highly accurate images of complex structures without the need for conventional surveying. The National Institute of Standards and Technology in Gaithersburg, Maryland, is designing a laser-based system to track the myriad of tools, materials, and equipment on construction sites. Riegl Laser Measurement designed its LMS-Z210 3-D Imaging Scanner to serve in three-dimensional measurement applications that are too complex for traditional theodolites to survey, including shipyards, quarries, vineyards, and crime scenes. Riegl USA expects to begin several projects using the 3-D scanner to continuously monitor bulk material piles in the wood and corn processing industries to improve process management and control.

scholarly journals General Synthetic Route and Structural Characterization of New 3d-4f Materials

2014 ◽  
Vol 70 (a1) ◽  
pp. C1775-C1775
Author(s):  
Andres Vega ◽  
Bianca Baldo ◽  
Veronica Paredes-García ◽  
Evgenia Spodine ◽  
Diego Venegas-Yazigi
Keyword(s):  
Structural Characterization ◽  
Crystal Engineering ◽  
Three Dimensional ◽  
Building Blocks ◽  
Point Of View ◽  
Lanthanide Ions ◽  
Synthetic Route ◽  
Metal Centers ◽  
Design And Synthesis ◽  
Potential Applications

Within the field of coordination chemistry, the crystal engineering has been applied mainly through the design and synthesis of Metal-Organic Materials (MOMs), which are attractive not only by the wide variety of architectures and topologies that they present, but also by the potential applications in catalysis, ion exchange, molecular adsorption, fluorescence, nonlinear optics, and magnetism. From a structural and synthetic point of view, the literature shows that a wide variety of MOMs ranging from 0D to 3D structures have been rationally designed and synthesized by the appropriate selection of the metal centers and organic building blocks, as well as of the reaction pathways.1-3 In this work, we present the a general synthetic route and the structural characterization to a new MII(3d)-M'III(4f) (M = Co, Ni ; M' = Ce) MOMs. The assembly of paramagnetic ions of transition metal centers together with simple and versatile ligands permits to obtain this new heterometallic three dimensional structures. From a structural point of view, the 3D MOM, present a cubic structure and crystallizes in the Fm-3m spatial group. Details of synthetic methodology and structural characteristic of the synthesized MOM should be discussed. Figure 1: Lanthanide ions are cubically surrounded by transitions ions which defines a covalent cubic tridimensional lattice. Acknowledgements: The authors acknowledge financial support from FONDECYT 1130643 and Financiamiento Basal, FB0807. B.B. thanks UNAB Doctoral Scholarship 2013 and CONICYT Fellowship.

A quaternion-based simulation of multirotor dynamics

2015 ◽  
Vol 06 (01) ◽  
pp. 1550009 ◽  
Author(s):  
Valeria Artale ◽  
Cristina L. R. Milazzo ◽  
Angela Ricciardello
Keyword(s):  
Rigid Body ◽  
Euler Equations ◽  
Body Condition ◽  
Rotational Motion ◽  
Three Dimensional ◽  
Euler Angle ◽  
Dynamical Model ◽  
Control Technique ◽  
Coordinate Space ◽  
And Control

The main problem addressed in this paper is the quaternion-based trajectory control of a microcopter consisting of six rotors with three pairs of counter-rotating fixed-pitch blades, known as hexacopter. If the hypothesis of rigid body condition is assumed, the Newton–Euler equations describe the translational and rotational motion of the drone. The standard Euler-angle parametrization of three-dimensional rotations contains singular points in the coordinate space that can cause failure of both dynamical model and control. In order to avoid singularities, all the rotations of the microcopter are thus parametrized in terms of quaternions and an original proportional derivative (PD) regulator is proposed in order to control the dynamical model. Numerical simulations will be performed on symmetrical flight configuration, proving the reliability of the proposed PD control technique.

A General Framework for Rigid Body Dynamics, Stability, and Control

2002 ◽  
Vol 124 (2) ◽  
pp. 241-251 ◽  
Author(s):  
Hooshang Hemami
Keyword(s):  
Rigid Body ◽  
Three Dimensional ◽  
Stability Control ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
Point Of View ◽  
Body System ◽  
Computationally Efficient ◽  
Augmented State ◽  
And Control

Augmented state spaces for the representation of systems that include rigid bodies, actuators, controllers, and integrate mechanical, electrical, sensory, and computational subsystems, are proposed here. The formulation is based on the Newton-Euler point of view, and has many advantages in stability, control, simulation, and computational considerations. The formulation is developed here for a one- and two-link three-dimensional rigid body system. Three simulations are presented to study stability of the system and to demonstrate feasibility and application of the formulation. The formulation affords an embedding of the system in a larger state space. The rigid body system can be stabilized, in the sense of Lyapunov, in this larger space with very general and minimally restricted feedback structures. The formulation is modular to implementation and is computationally efficient. The method offers alternative states that are easier to control and measure than Euler angles. Thus, the formulation offers advantages from a sensory and instrumentation point of view. The formulation is versatile, and yields conveniently to applications in studies of human neuro-musculo-skeletal systems, robotic systems, marionettes and humanoids for animation and simulation of crash and other injury prone maneuvers and sports. It offers a methodical and systematic procedure for formulation of large systems of interconnected rigid bodies.

scholarly journals The Response of Residents of the Building and Non-structural Components, in Contrast to Explosions at Ground Level from the Standpoint of Passive Defense

2019 ◽  
Vol 5 (2) ◽  
pp. 495 ◽  
Author(s):  
MohammadReza Mozaffarpour Taromi ◽  
Hossein Khosravi
Keyword(s):  
Linear Time ◽  
Time History ◽  
Ground Level ◽  
Point Of View ◽  
Structural Elements ◽  
High Rise ◽  
Healthy State ◽  
History Analysis ◽  
Serious Injuries ◽  
And Control

The research by non-military research associations and assemblies on explosion have increased due to the growth in the death and damage rates resulting from explosion, particularly blasts induced by terroristic invasions which mostly occur on the ground. Most studies are conducted with a major focus on strengthening the structures against explosions. Further, scholars have focused on resistance and ductility criteria required for the design and control over structural elements. Now, the question is whether the health of a structure can represent its inhabitants’ health. Few studies have been done on the convenience of inhabitants and response of non-structural elements, which are limited to impact of vibrations on high-rise structures caused by the loads imposed by wind and earthquake. The important factors relevant to the health and convenience of building inhabitants are as follows: speed, acceleration, and variations in the acceleration of floors.In this paper, the aforementioned parameters are measured, according to which the convenience and health of inhabitants were assessed. For this purpose, two 4-story and 8-story buildings were selected on which four selective explosions were applied. The results were then presented in two forms of maximum values and dynamic response by performing dynamic modal linear time history analysis. The building's response under typical forces such as dead and live and earthquake forces was remarkably desirable and the behavior remained linear, but the building’s acceleration may cause serious injuries in terms of human comfort criteria. The obtained results indicated that the healthy state of the structure does not represent the health of the building inhabitants. Further, although the building was safe against the elective blasts, the lateral accelerations were capable of imposing significant damages to the building residents. This can be considered as a criterion for control and future designs from a passive defense point of view, as the explosions induced by terroristic attacks is increasing.

Designing TIMP (tissue inhibitor of metalloproteinases) variants that are selective metalloproteinase inhibitors

2003 ◽  
Vol 70 ◽  
pp. 201-212 ◽  
Author(s):  
Hideaki Nagase ◽  
Keith Brew
Keyword(s):  
Three Dimensional ◽  
Therapeutic Interventions ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Structural Basis ◽  
Structural Elements ◽  
Ridge Structure ◽  
Extracellular Matrix Components ◽  
Metalloproteinase Inhibitors ◽  
The Matrix ◽  
A Disintegrin And Metalloproteinase

The tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of the matrix metalloproteinases (MMPs), enzymes that play central roles in the degradation of extracellular matrix components. The balance between MMPs and TIMPs is important in the maintenance of tissues, and its disruption affects tissue homoeostasis. Four related TIMPs (TIMP-1 to TIMP-4) can each form a complex with MMPs in a 1:1 stoichiometry with high affinity, but their inhibitory activities towards different MMPs are not particularly selective. The three-dimensional structures of TIMP-MMP complexes reveal that TIMPs have an extended ridge structure that slots into the active site of MMPs. Mutation of three separate residues in the ridge, at positions 2, 4 and 68 in the amino acid sequence of the N-terminal inhibitory domain of TIMP-1 (N-TIMP-1), separately and in combination has produced N-TIMP-1 variants with higher binding affinity and specificity for individual MMPs. TIMP-3 is unique in that it inhibits not only MMPs, but also several ADAM (a disintegrin and metalloproteinase) and ADAMTS (ADAM with thrombospondin motifs) metalloproteinases. Inhibition of the latter groups of metalloproteinases, as exemplified with ADAMTS-4 (aggrecanase 1), requires additional structural elements in TIMP-3 that have not yet been identified. Knowledge of the structural basis of the inhibitory action of TIMPs will facilitate the design of selective TIMP variants for investigating the biological roles of specific MMPs and for developing therapeutic interventions for MMP-associated diseases.

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