Amado George Stefan

Dr. Amado George Stefan


Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
Verified
Journal Article
Open access
PDF file
Dragos CretoiuDragos Cretoiu
Dragos Cretoiu
SRSimona Roatesi
Simona Roatesi
IBIon Bica
Ion Bica
CPCezar Plesca
Cezar Plesca
ASAmado George Stefan
Amado George Stefan
Sanda Maria CretoiuSanda Maria Cretoiu
Sanda Maria Cretoiu
Background: Telocytes (TCs) are unique interstitial or stromal cells of mesodermal origin, defined by long cellular extensions called telopodes (Tps) which form a network, connecting them to surrounding cells. TCs were previously found around stem and progenitor cells, and were thought to be most likely involved in local tissue metabolic equilibrium and regeneration. The roles of telocytes are still under scientific scrutiny, with existing studies suggesting they possess various functions depending on their location. Methods: Human myometrium biopsies were collected from pregnant and non-pregnant women, telocytes were then investigated in myometrial interstitial cell cultures based on morphological criteria and later prepared for time-lapse microscopy. Semi-analytical and numerical solutions were developed to highlight the geometric characteristics and the behavior of telocytes. Results: Results were gathered in a database which would further allow efficient telocyte tracking and indexing in a content-based image retrieval (CBIR) of digital medical images. Mathematical analysis revealed pivotal information regarding the homogeneity, hardness and resistance of telocytes’ structure. Cellular activity models were monitored in vitro, therefore supporting the creation of databases of telocyte images. Conclusions: The obtained images were analyzed, using segmentation techniques and mathematical models in conjunction with computer simulation, in order to depict TCs behavior in relation to surrounding cells. This paper brings an important contribution to the development of bioinformatics systems by creating software-based telocyte models that could be used both for diagnostic and educational purposes.

30 August 2023 in Mathematics
Verified
Journal Article
Open access
PDF file
OAOctavian Alexa
Octavian Alexa
CTCiobotaru Ticusor
Ciobotaru Ticusor
LGLucian Stefanita GRIGORE
Lucian Stefanita GRIGORE
Teodor Lucian GrigorieTeodor Lucian Grigorie
Teodor Lucian Grigorie
ASAmado George Stefan
Amado George Stefan
CVCristina Vlădescu
Cristina Vlădescu
This paper presents mathematical models to estimate the kinematics and dynamics of wheeled and tracked robots. The models account for the physical–mechanical characteristics of the ground, the influence of the center of gravity displacement on the cornering moment of resistance, and the influence of the interaction of the crawler with the roadway. The results of the models are characterized by defining computational relationships for a robot’s equations of motion, longitudinal forces, transverse forces, and resistive turning moments generated via longitudinal forces and transverse forces.

15 March 2023 in Drones
Verified
Journal Article
Open access
PDF file
ATAndra TOFAN-NEGRU
Andra TOFAN-NEGRU
ASAmado George Stefan
Amado George Stefan
LGLucian Stefanita GRIGORE
Lucian Stefanita GRIGORE
Ionica OncioiuIonica Oncioiu
Ionica Oncioiu
The aim of the paper is to validate the analytical–numerical analysis method regarding the operating regime of the propellers of a quadcopter. The research aims to mark the flow areas whose numerical results differ from the experimental ones and to investigate the possible reasons for the discrepancies between the values. The paper presents the determination of the air velocity produced by the rotational movement of a quadcopter propeller for a stationary position of the drive motor. The velocities were determined both experimentally at various points located below the propeller plane using hot-wire anemometric probes and numerically using a time-lapse simulation with a rotating sliding table. The numerical simulations carried out consisted of the determination of the time variation of the velocity distribution developed by the propeller in the rotational movement for the different operating (power) cycles of the engine. In addition, a technique that utilizes reverse engineering to determine the propeller profile, the anemometric probe calibration, and the average velocity values measured at various points below the propeller plane for engine operating regimes that range from 60 to 90% are also presented.

28 July 2022 in Electronics
Verified
Journal Article
Open access
PDF file
ASAmado George Stefan
Amado George Stefan
LGLucian Stefanita GRIGORE
Lucian Stefanita GRIGORE
Ionica OncioiuIonica Oncioiu
Ionica Oncioiu
DCDaniel Constantin
Daniel Constantin
ȘMȘtefan Mustață
Ștefan Mustață
DGDamian Gorgoteanu
Damian Gorgoteanu
Terrestrial robots are being employed in a variety of sectors and for a variety of objectives. The purpose of this paper is to analyze and validate an analytical–numerical model of a robotic arm’s behavior. The proposed robot was designed to replace human personnel who remove ammunition or explosive devices. At the same time, the influence of the stiffness of the EOD robotic arm on the position of the effector in a variety of geometric task configurations was investigated. In order to obtain results relevant to the investigation, the angles of rotation under the load of each component of the arm’s composition and the vertical movement of the effector were measured. The main conclusions emphasize that a lower stiffness comes from the components of linear motors, which act on the elements of the robotic arm, and they substantially influence the elastic behavior of the arm. In addition, the constructive components of the arm have high rigidity compared to those of the linear actuators.

6 September 2023 in Biomimetics
Verified
Journal Article
Open access
PDF file
Marius-Valentin DrăgoiMarius-Valentin Drăgoi
Marius-Valentin Drăgoi
AHAnton HADAR
Anton HADAR
NGNicolae Goga
Nicolae Goga
BFBaciu Florin
Baciu Florin
ASAmado George Stefan
Amado George Stefan
Ionica OncioiuIonica Oncioiu
Ionica Oncioiu
The purpose of prosthetic devices is to reproduce the angular-torque profile of a healthy human during locomotion. A lightweight and energy-efficient joint is capable of decreasing the peak actuator power and/or power consumption per gait cycle, while adequately meeting profile-matching constraints. The aim of this study was to highlight the dynamic characteristics of a bionic leg with electric actuators with rotational movement. Three-dimensional (3D)-printing technology was used to create the leg, and servomotors were used for the joints. A stepper motor was used for horizontal movement. For better numerical simulation of the printed model, three mechanical tests were carried out (tension, compression, and bending), based on which the main mechanical characteristics necessary for the numerical simulation were obtained. For the experimental model made, the dynamic stresses could be determined, which highlights the fact that, under the conditions given for the experimental model, the prosthesis resists.

17 May 2021 in Engineering Proceedings
Verified
Conference Paper
Open access
PDF file
LGLucian Stefanita GRIGORE
Lucian Stefanita GRIGORE
ASAmado George Stefan
Amado George Stefan
Ionica OncioiuIonica Oncioiu
Ionica Oncioiu
CMCristian-Constantin Molder
Cristian-Constantin Molder
DGDamian Gorgoteanu
Damian Gorgoteanu
RBRăzvan-Ionuț Bălașa
Răzvan-Ionuț Bălașa
This article presents aspects related to the protection (with a double shield made of stainless steel) of a robot for emergency situations against the effect of flames due to a fire. The ground robot is semi-autonomous/autonomous, with a wheeled propeller (6 × 6). The robot, designed and built at the TRL 2 level, is intended for fire investigation, monitoring, and intervention (and, in particular, for petrochemical plants). The role of the shield is to protect the equipment that is part of the robot including its controllers, sensors, communications, power supply, etc. The need to mount a thermal protection shield on the intervention robot was given by the fact that fires at petrochemical plants generate very large thermal fields and gradients which are responsible for creating blind spots. These blind spots do not allow intervention crews to see what is happening in that area. These blind spots are characterized by very high temperatures. The dynamics of these fires can be unpredictable. Therefore, to analyze the performance of the heat shield in this study we perform a numerical-experimental analysis.