Veturia Chiroiu

Veturia Chiroiu
Institute of Solid Mechanics, Romanian Academy · Deformable Media and Ultrasonics

Doctor in Mathematics

About

217
Publications
16,732
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
635
Citations
Citations since 2016
45 Research Items
202 Citations
2016201720182019202020212022010203040
2016201720182019202020212022010203040
2016201720182019202020212022010203040
2016201720182019202020212022010203040
Introduction
Veturia Chiroiu received the PhD degree in Mathematics from the University of Bucharest in 1981. Since 1966 she has been working as a research fellow at the Institute of Solid Mechanics of the Romanian Academy. Currently, she is the head of Department of Continuum Mechanics. She received a Fulbright Fellowship to work at Princeton University, Department of Aerospace and Mechanical Science (1972–1973), has led various research projects (Copernicus, NATO).
Additional affiliations
October 1966 - present
Institutul de Mecanica Solidelor
Position
  • Researcher
Description
  • Veturia Chiroiu received the PhD degree in Mathematics from the University of Bucharest in 1981. Since 1966 she has been working as a research fellow at the Institute of Solid Mechanics of the Romanian Academy. Currently, she is the head of Department of Continuum Mechanics. She received a Fulbright Fellowship to work at Princeton University, Department of Aerospace and Mechanical Science (1972–1973), has led various research projects (Copernicus, NATO), and lectured in foreign in
Education
October 1966 - October 1971
University of Bucharest
Field of study
  • Methematics

Publications

Publications (217)
Article
The cnoidal method is applied to solve the set of nonlinear dynamic equations of the left ventricle. By using the theta-function representation of the solutions and a genetic algorithm, the ventricular motion can be described as a linear superposition of cnoidal pulses and additional terms, which include nonlinear interactions among them.
Article
Full-text available
The paper discusses the behavior of beams with external damping patches made of auxetic materials. The damping force is modeled by using the nonlocal theory. Unlike the local models, the nonlocal damping force is modeled as a weighted average of the velocity field over the spatial domain, determined by a kernel function based on distance measures....
Article
The sound attenuation in a sonic composite is studied using a new method that combines the features of the piezoceramic theory, cnoidal method and genetic algorithms. A sonic composite consists of an array of acoustic scatterers embedded in an epoxy matrix. Acoustic scatterers are piezoceramic hollow spheres made from functionally graded materials...
Article
Full-text available
The configuration for a semi-infinite strip with self tuning based control is presented in this paper. The semi-infinite strip is composed from a layer of main material, and another layer of piezoelectric material with Cantor-like structure. We show that the displacements distribution can be controlled actively by applying a voltage to the piezoele...
Article
Full-text available
Damping is an irreversible physical process that dissipates energy through the conversion of work into heat. In engineering structures it is present in several forms: internal hysteresis, friction via the rubbing action of surfaces or particles, viscous friction in fluids, radiation damping, electromagnetic damping etc. Damping plays a very importa...
Article
Chalcogenide thin films based on Ge-Sb-Te (GST) are synthesized from elements with 5N purity using the conventional melt-quenching method. The mixture was used as material for deposition on quartz substrate by the chemical vacuum deposition method. Spectro-ellipsometry measurements determined optical and dielectric properties. The optical dispersio...
Article
We report the deformation of the needle during its insertion into the human liver in the context of surgery simulation of the high-robotic-assisted intraoperative treatment of liver tumors based on the integrated imaging-molecular diagnosis. The bee needle is modeled as a flexible thread within the framework of the nonlinear elasticity theory. The...
Article
Full-text available
Structural damages could appear in any mechanical parts. New methods for their structural monitoring would be a good way to estimate structural strength and, consequently, its capacity to efficiently assist people in need, even for health recovery (surgery, severe illness cure), or for improving the lives of the visually impaired. Mechanical damage...
Article
Full-text available
In this paper we consider two situations. In the first, all kinematic chains are elastic, while the second situation is characterized by one rigid kinematic chain, with the rest of them being elastic. In addition, the kinematic joints are considered to be rigid. The calculations are performed using the screw coordinates. For the free vibrations of...
Chapter
This paper presents an evaluation of the stiffness and eigenmodes of a Stewart platform during changing positions in the workspace. Stiffness and eigenmodes are important in the design phase and even during service they can be useful for the detection of damages that could appear in the structure. Computer simulation is used to solve the mathematic...
Chapter
We report in this paper the subharmonic generation of waves in GeSbSe chalcogenide glasses architectured as Cantor-like structures. The subharmonic waves generation is explained as a superposition of waves in both phonon and fracton vibration regimes.
Article
Full-text available
We address an alternative road traffic noise barrier as a sonic composite consisted of an array of acoustic scatterers embedded in air. Acoustic scatterers are piezoceramic hollow spheres of functionally graded materials-the Reddy graded hollow spheres. Multiple (Bragg) scattering lead to a selective sound attenuation in the frequency bands called...
Conference Paper
Full-text available
Using robots with Gough-Stewart parallel mechanical chain configuration can bring many advantages but also disadvantages. The most important constraint of these types of robots is related to the free-singularity workspace. But adjacent to it, there are also the constraints related to the speeds of the manipulator (end-effector) given by the limitat...
Conference Paper
Full-text available
The environment has various characteristics related to temperature, dust, pollution, chemicals, etc. Each environmental parameter could have an influence on the robot's performance. The influence of thermal behavior is researched for a hexapod-parallel robot using analytical methods of forwarding kinematics. The effect of the temperature on the act...
Article
Full-text available
We present a novel control system based on the capturing of the motion and the intent of the motion of each subject engaged into an action (a game for example) monitored by a mobile supervising robot. The robot observes the subjects' activity and spatio-temporal motions starting from zero information regarding the field of view and the rules of gam...
Article
Full-text available
In this paper, three deposition techniques are combined to create a window material with high average transmission at oblique angles of incidence. Spectrophotometry and ellipsometry measurements, respectively, yield the optical constants n and k. In contrast with other analyses on the subject, a high average transmission, higher than 91% in the 450...
Article
Full-text available
Given five pairs of attachment points of a planar platform, there exists a sixth point pair so that the resulting planar architecturally singular platform has the same solution for the direct kinematics. This is a consequence of the Prix Vaillant problem posed in 1904 by the French Academy of Science. The theorem discusses the displacements of cert...
Article
Full-text available
The purpose of this paper is to study the subharmonic wave propagation in Ge x Sb 40-x Se 60 with composition 12, 25 and 30 at.%, synthesized from elements with 5N purity (Ge, Sb, Se) by the conventional melt-quenching method. The plate has a Cantor-like structure. The subharmonic generation of waves is due to the fractal features of chalcogenides...
Article
Full-text available
In the present research, the navigation of a flexible needle into the human liver in the context of the robotic-assisted intraoperative treatment of the liver tumors, is reported. Cosserat (micropolar) elasticity is applied to describe the interaction between the needle and the human liver. The theory incorporates the local rotation of points and t...
Chapter
Full-text available
The insertion of the needle is difficult because the deformation and displacement of the organs are the key elements in the surgical act. Liver and tumor modeling are essential in the development of the needle insertion model. The role of the needle is to deliver into the tumor an active chemotherapeutic agent. We describe in this chapter the defor...
Article
Abstract. Compared to the rapid development of design methods, the optimization of the GeSbSe layer design is still lagging behind. Accordingly, the layer design should be acceptable for existing methods. Optimum selection of GeSbSe layer design in connection to transmission and thickness choice is discussed. The GexSb40−xSe60 (x ¼ 12, 25, and 30 a...
Article
Full-text available
The purpose of this paper is to study the sliding mode control as a Ricci flow process in the context of a three-story building structure subjected to seismic waves. The stability conditions result from two Lyapunov functions, the first associated with slipping in a finite period of time and the second with convergence of trajectories to the desire...
Article
Full-text available
The uncertainties of the optical transmission and absorbance measurements of thin films GexSb40−xSe60 (x = 12, 25, and 30 at.%) are investigated in this paper. To obtain additional measurements, a technique is proposed based on the global volumetric deformation technique. The thin films are synthesized from elements with 5 N purity (Ge, Sb, Se) by...
Preprint
Full-text available
The purpose of this paper is to study the sliding mode control as a Ricci flow process in the context of a three-story building structure subjected to seismic waves. The stability conditions result from two Lyapunov- functions, the first associated with slipping in a finite period of time, and the second with convergence of trajectories to the desi...
Article
Chalcogenide glasses studied in this paper are based on thin films Ge x Sb 40-x Se 60 with composition x  12, 25 and 30 at.%, synthesized from elements with 5N purity (Ge, Sb, Se) by the conventional melt-quenching method. The glasses are characterized by highly optical nonlinear properties. The electronic and structural properties are introduced,...
Chapter
Sonoelasticity imaging is a method for assessing the stiffness, or elastic constants, of tissues, belonging to a large class of inverse medium scattering problems in perturbed media. Sonoelasticity is also known as sonoelastography. The technique is based on the propagation of low amplitude, low frequency shear waves (less than 0.1 mm displacement...
Preprint
Full-text available
We address an alternative road traffic noise barrier as a sonic composite consisted of an array of acoustic scatterers embedded in air. Acoustic scatterers are piezoceramic hollow spheres of functionally graded materials-the Reddy graded hollow spheres. Multiple (Bragg) scattering lead to a selective sound attenuation in the frequency bands called...
Chapter
Full-text available
We study a model for a multiple-needle robot based on the Fibonacci sequence scaling. The paper determines the collision-free trajectories of the robot who is carrying drugs into a tumoral target. The purpose of the paper is to predict the insertion trajectories for all needles so as the trajectories should avoid the collisions to ribs, blood vesse...
Article
Chalcogen thin films Ge x Sb 40-x Se 60 with the composition x = 12, 25, and 30 (atomic percentage) at.%, have been synthesized from elements with 99.999% purity (Ge, Sb, Se) by the conventional melt quenching method. The quartz ampoule containing the mixture of elements with proper weight percent was evacuated down to a pressure of 10-3 Pa. The pa...
Article
Full-text available
Chalcogenide glasses Ge x Sb 40−x Se 60 with composition 12, 25 and 30 at.%, synthesized from elements with 5N purity (Ge, Sb, Se) by the conventional melt-quenching method were studied. The spectrophotometer’s measurements were recorded to determine the optical properties. Models based on the absorbance and absorption coefficient are used to deter...
Article
Full-text available
By extending the linear equivalence method (LEM), the nonlinear equations of a two link flexible manipulator are obtained as a linear superposition of Coulomb vibrations. In addition, the nonlinear phenomena of dynamic responses such as internal resonance has investigated. We show that the solutions allow a qualitative analysis not only of the quas...
Article
Full-text available
The chalcogenide ternary thin films should provide efficient solutions to develop the color filter-free image sensors for rapid capture of vivid colors detection of the motion images of a scene in the cognitive processes of perception and interpretation of motion. The image sensor consists of a light-sensitive cell having a lower and a higher elect...
Article
Full-text available
We report on the dielectric properties of the chalcogenide ternary GexSb40−xSe60 glasses with composition x = 12, 25, 30 at%. By combining the Swanepoel method with a formalism based on the Hilliard theory of the surface tension, the linear dielectric constants and the third-order optical susceptibility are predicted. The glasses are synthesized fr...
Article
Full-text available
The inverse sonification problem is investigated in this article in order to detect hardly capturing details in a medical image. The direct problem consists in converting the image data into sound signals by a transformation which involves three steps - data, acoustics parameters and sound representations. The inverse problem is reversing back the...
Article
Full-text available
The goal of this study is to model the muscle-tendon function as observed in the human walking. The muscle-tendon units dorsiflex the ankle, flex and extend the knee and also accelerate the joint motions. A spring model is proposed to describe the action of a unit muscle-tendon in a gait cycle of human walking. The role of the elasticity in the mus...
Article
Full-text available
A hybrid logic algorithm is presented for extending the control of a cooperatively robotic system by including uncertain input conditions and the hard and soft stops. The method can be used in surgical interventions where the robot and the physician are working with the same surgical tool. The results show that the algorithm improves the trajectory...
Article
In this paper, a sonification algorithm for developing the off-road models for driving simulators, is proposed. The aim of this algorithm is to overcome difficulties of heuristics identification which are best suited to a particular off-road profile built by measurements. The sonification algorithm is based on the stochastic polynomial chaos analys...
Article
The cnoidal method is used to analyse the behaviour of multilayer films with randomly inserted defects. These structures have a significant potential to architectural acoustics. The film is consisted of alternating layers of material with different mechanical properties, following a triadic Cantor sequence, and despite of its non-periodicity, it be...
Article
A 2D acoustic cloak surrounding an object to make it acoustically "invisible" when the sound is incident from any direction and passes through and around the cloak, is discussed in this paper. The key for "invisibility" is the coordinate transformation which design the metamaterial required for a given application. The acoustic cloaking is based on...
Article
The goal of this paper is to discuss the technique of controlling the mechanical properties of sonic composites. The idea is to architecture the scatterers and material from which they are made, their number and geometry in order to obtain special features in their response to external waves. We refer to perfectly reflecting of acoustical waves ove...
Article
A flexible finger with muscles made of Nitinol wires and the skin made of auxetic material is analyzed from the tactile sensing point of view. The recognizing of the shape and texture of 3D objects is performed by simulation the action of an array of nanopiezotronic transistors integrated into the skin. The array of nanopiezotronic transistors make...
Conference Paper
This paper deals with the development of a Driving Simulator actuated by pneumatic muscles. So that the correct mechanical structure could be yielded, several investigations have been carried out, i.e. topology analyses, kinematic analysis and workspace investigations. Parallel platforms actuated by fluidic muscles represent an unusual design of dr...
Article
Full-text available
A non-periodic multilayer film was analyzed to show that, despite its non-periodicity, the film exhibits full band-gaps and localized modes at its interfaces, as well as in the sonic composites. The film consists of alternating layers of two different materials that follow a triadic Cantor sequence. The Cantor structure shows extremely low threshol...
Article
This paper concerns a simplified 7 DOF model for car vertical vibrations. The classical 7 DOF of the considered 3D vertical model are: the vertical displacement of the gravity center of the car body, the roll and pitch angles of the car body and the four vertical displacements of the wheels centers. Using the x-y-z sequence of rotations parameteriz...
Article
This work is focused on the compressive behavior in the elastic region of a composite material made out of stalk-based maize fiber and unsaturated polyester resin polymer as matrix with methyl ethyl ketone peroxide as a catalyst and Cobalt Octoate as a promoter [1]. Deformation and fracture behavior are investigated by using Extended Finite Element...
Article
The paper discusses the chaotic behavior of a vibrating structure coupled to an energy source. The structural response of this system may act like energy sink under certain conditions so that a part of the energy supplied by the source is spend to vibrate the structure rather than increasing the drive speed, according to the Sommerfeld effect [1]....
Article
Driving simulators are complex technical entities for reproducing the phenomena of real driving. One of their essential components is the visual simulator. For the purpose of creating the visual simulator it is of utmost importance to generate the 3D surfaces such that they simulate both the road and the environment. In this paper, the problem of t...
Conference Paper
3D objects and generation of surfaces are important issues in several areas, such as simulators and games. There are different methods of approach to this subject: methods based on interpolation, using Voronoi diagrams and even unusual ones, based on Fractal Theory. This article presents and explores a method, which combines basic Geometry and prob...
Article
Driving simulators represent a novel way to reproduce the movements of a vehicle with the purpose of testing different cars, to prevent dangerous situations, entertainment and also to train the professional drivers. More, they are used to render the effects of the interactions between the car and the road, as a consequence of the constrains imposed...
Article
In this paper, a virtual experiment concerning driving on off-roads is investigated via 3D normal vibro-contact problem with friction. The dynamic road concept is introduced in order to characterize a particular stretch of road by total longitudinal, lateral, and normal forces and their geometric distributions in the contact patches. The off-road p...
Article
Full-text available
In this paper, the cyclic behavior of a superelastic-plastic nitinol cubic block is described by using the Bouc–Wen model coupled to an intrinsic time measure other than clock time, which governs the behavior of the materials. As a consequence, the thermodynamic admissibility of the Bouc–Wen model is provided by the endochronic theory of plasticity...
Article
Full-text available
In this paper, a virtual experiment concerning driving on off-roads is investigated via 3D normal vibro-contact problem with friction. The dynamic road concept is introduced in order to characterize a particular stretch of road by total longitudinal, lateral, and normal forces and their geometric distributions in the contact patches. The off-road p...
Article
A flexible finger with muscles made of Nitinol wires and the skin made of auxetic material is analyzed from the tactile sensing point of view. The recognizing of the shape and texture of 3D objects is performed by simulation the action of an array of nanopiezotronic transistors integrated into the skin. The array of nanopiezotronic transistors make...
Article
Full-text available
The behaviour of a dynamic system governed by Sommerfeld effect is studied in this paper. We refer to a small building equipped with an electromechanical vibration absorber subjected to harmonic excitation with time dependent frequencies and random vibrations, respectively. This structure is a non-ideal system which acts like an energy sink for whi...
Article
Full-text available
The car vertical dynamics simulations in this paper concern only the roll and the pitch motion of the car body. Two different simulators are aimed to be used in parallel. The first simulator considered is CARSIM commercial software, while the second variant is an in-house simulator based on a 7 DOF car vertical dynamics model, which concerns only t...
Article
The sound attenuation in a sonic composite is studied by using the cnoidal method combined with the features of the piezoceramic theory. The solutions of nonlinear equations which govern the behavior of the sonic composites are written as a sum of a linear and nonlinear cnoidal functions. A sonic composite consists of an array of acoustic scatterer...
Article
In this work, analysis of the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. The case of harmonic excitation with constant or time dependent frequencies is considered. The interaction between the structure and the energy source is analyzed via the Sommerfeld effect inside the resona...
Article
The present paper points out the scenario of the hyperchaotic attractor formation (an attractor with at least two positive Lyapunov exponents) in a class of models governed by the Sommerfeld effects. The Sommerfeld effect is the result of the conservation law of energy. When a dynamical system is coupled to a power source, it acts like a energy sin...
Article
Full-text available
A new approach to obtain various architectures for auxetic foams by using the property of Helmholtz equation to be invariant under geometric transformations is described in this paper. The versatility of the geometric transformations is illustrated in order to obtain the auxetic version from the conventional foam.
Conference Paper
This paper define and analyze the new concept of reconfigurable simulator avatar. A simulator avatar is a fully integrated computer model of a driving simulator. The simulator is a useful tool for driving simulators development because it allows implementation and validation of different working hypotheses and layouts for driving simulators topolog...
Conference Paper
In the paper the concept of a simulation avatar for a driver simulator is proposed. The SIMulation AVatar (SIMAV) for a driving simulator is understood as a fully integrated computer model of all driving simulator components: car (AVC), road (AVR) and driver (AVD). Based on the proposed concept the AVC for a 4×4 independent suspension vehicle is de...
Article
Transformation acoustics opens a new avenue towards the architecture, modeling and simulation of a new class of sonic composites with scatterers made of various materials and having various shapes embedded in an epoxy matrix. The design of acoustic scatterers is based on the property of Helmholtz equations to be invariant under a coordinate transfo...
Article
Full-text available
The intrinsic time, other than the clock time which governs the behavior of the materials, was introduced by Valanis [13] in order to develop the endochronic, which is a theory of viscoplasticity without a yield surface. Erlicher and Point [12] have proved the thermodynamic admissibility of the Bouc-Wen model, by adopting the endochronic theory. Th...
Article
Geometric transformations are strongly sustained by manufacture of auxetic materials based on the pore size reduction through radial compression molds. In addition, geometric transformations underlie the development of seismic cloaking. The spatial compression of the conventional foams is determined by the shape of the cloaked object. The cloaking...
Article
A vibrating system is said ideal when its excitation is not influenced by the response of the system. When the excitation is influenced by the response of the system, the system is said non-ideal. A new degree of freedom is present in such systems, for which a new equation has to be added in order to describe how the energy source interacts with th...
Article
The sound attenuation in a sonic composite without/with point defects is studied using a new method that combines the features of the cnoidal method and the genetic algorithm. Acoustic scatterers are composed by piezoceramic hollow spheres of functionally graded materials—the Reddy and cosine graded hollow spheres. This method enables to obtain the...
Article
In this work, the analysis the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. In the first part, the case of harmonic excitation with constant or time dependent frequencies is considered, and in the second part, the case of random earthquakes, respectively. The cross correlation fun...