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One of the major challenges in the science of maxillofacial radiology imaging is the various artifacts created in images taken by cone beam computed tomography (CBCT) imaging systems. Among these artifacts, motion artifact, which is created by the patient, has adverse effects on image quality. In this paper, according to the conditions and limitations of the CBCT imaging room, the goal is the design and development of a cable-driven parallel robot to create repeatable movements of a dry skull inside a CBCT scanner for studying motion artifacts and building up reference datasets with motion artifacts. The proposed robot allows a dry skull to execute motions, which were selected on the basis of clinical evidence, with 3-degrees of freedom during imaging in synchronous manner with the radiation beam. The kinematic model of the robot is presented to investigate and describe the correlation between the amount of motion and the pulse width applied to DC motors. This robot can be controlled by the user through a smartphone or laptop wirelessly via a Wi-Fi connection. Using wireless communication protects the user from harmful radiation during robot driving and functioning. The results show that the designed robot has a reproducibility above 95% in performing various movements.
The optimum selection of a structure for a given application is a capital phase in typological synthesis of parallel robots. To help in this selection, this paper presents a performance evaluation of four translational parallel robots: Delta, 3-UPU, Romdhane-Affi-Fayet, and Tri-pyramid (TP). The problem is set as a multiobjective optimization using genetic algorithm methods, which uses kinematic criteria, that is, global dexterity and compactness, to ensure a prescribed workspace. The results are presented as Pareto fronts, which are used to compare the performances of the aforementioned structures. The obtained results show that the TP robot has the best kinematic performance, whereas the 3-UPU robot is the most compact for a given prescribed workspace.
Serial spherical linkages have been used in the design of a number of robots for minimally invasive surgery, in order to mechanically constrain the surgical instrument with respect to the incision. However, the typical serial spherical mechanism suffers from conflicting design objectives, resulting in an unsuitable compromise between avoiding collision with the patient and producing good kinematic and workspace characteristics. In this paper, we propose a multi-robot system composed of two redundant serial spherical linkages to achieve this purpose. A multi-objective optimization for achieving the aforementioned design goals is presented first for a single redundant robot and then for a multi-robot system. The problem of mounting multiple robots on the operating table as well as the way cooperative actions can be performed is addressed. The sensitivity of each optimal solution (single-robot and multi-robot) to uncertainties in the design parameters is investigated.
The rheological and filtration properties of a Tunisian clay are presented and compared with those of Wyoming bentonite. The study was part of an evauation of Tunisian mining resources in general, and of the bentonitic deposits in particular. Qualitatively, the two clays exhibit the same rheological and filtration behaviour but quantitatively the properties of purified Wyoming bentonite are distinctly better at the same concentration. The difference can be related to the mineralogical structure and the presence of 13% illite in the Tunisian clay. Standard tests show that the rheological behaviour of the purified Tunisian clay is close to that of the raw Wyoming bentonite and conform to the American Petroluem Institute (A.P.I.) standards for medium-depth drilling formulations.
This paper introduces the design and the optimization of a probe holder robot for tele-echography applications. To define its kinematic architecture, an approach based on motion capture of an expert's gestures during ultrasound examinations was proposed. The medical gestures analyzed consisted of ultrasound probe movements and were used to characterize the kinematic specifications of the proposed manipulator. The selected architecture was a Spherical Parallel Mechanism (SPM) with 3 degrees of freedom (DoF) and its optimal synthesis was performed using real-coded Genetic Algorithms (GA). The optimization criteria and constraints were established thanks to the collaboration of medical experts and were successively formulated and solved using mono-objective and multi-objective functions.
The behaviour of clays is not still well understood. Most information
concerning clays has been obtained by techniques which give statistical
information on the structure and chemistry. However papers have reported
results from scanning and high resolution electron microscopy. This work
presents a nanoscopic approach, using electron energy loss spectroscopy
(EELS), of different purified clays. EELS permitted to detect all the
elements found by classical chemistry at a macroscopic level. In particular
it made it possible to determine the Si/Al ratio in kaolinite (Si/Al ~ 1), smectite and illite (Si/Al ~ 2). In all the cases, the K edge
oxygen energy loss near edge structure (ELNES) is often similar to that of
other clays we studied, but a strong heterogeneity has been observed. It was
also possible to highlight an influence of the presence of iron on the
profile of the oxygen peak.
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