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Search Results: 1 - 10 of 462094 matches for " Goodarzi A "
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Psychiatric and family functioning in children with leukemia and their parents
Goodarzi A
Tehran University Medical Journal , 1999,
Abstract: The present study reports data from a cross-sectional investigation of the psychiatric and psychosocial functioning of 55 children diagnosed with acute lymphocytic leukemia and their families at three points in time: diagnosis (newly diagnosed), 1 year postdiagnosis, and 1 year after the completion of chemotherapy (offtherapy). Results reveal minimal psychopathology in these children and their parents based on self-and informantreports and structured diagnostic interviews. These families appear to be functioning adequately and report more family cohesiveness and marital satisfaction after chemotherapy was completed. Coping strategies commonly used by children and their parents include problem solving, a positive outlook, and good communication. Implications for psychiatric consultation are presented.
Geometric Nonlinear Controls for Multiple Cooperative Quadrotor UAVs Transporting a Rigid Body
Farhad A. Goodarzi
Mathematics , 2015,
Abstract: This dissertation presents nonlinear tracking control systems for quadrotor unmanned aerial vehicles (UAV) under the influence of uncertainties. Assuming that there exist unstructured disturbances in the translational dynamics and the attitude dynamics, a geometric nonlinear adaptive controller is developed directly on the special Euclidean group. In particular, a new form of an adaptive control term is proposed to guarantee stability while compensating the effects of uncertainties in quadrotor dynamics. Next, we derived a coordinate-free form of equations of motion for a complete model of a quadrotor UAV with a payload which is connected via a flexible cable according to Lagrangian mechanics on a manifold. The flexible cable is modeled as a system of serially-connected links and has been considered in the full dynamic model. A geometric nonlinear control system is presented to asymptotically stabilize the position of the quadrotor while aligning the links to the vertical direction below the quadrotor. Finally, we focused on the dynamics and control of arbitrary number of quadrotor UAVs transporting a rigid body payload. The rigid body payload is connected to quadrotors via flexible cables. It is shown that a coordinate-free form of equations of motion can be derived for arbitrary numbers of quadrotors and links according to Lagrangian mechanics on a manifold. A geometric nonlinear controller is presented to transport the rigid body to a fixed desired position while aligning all of the links along the vertical direction. Numerical simulation and experimental results are presented and rigorous mathematical stability analysis are provided. These results will be particularly useful for aggressive load transportation that involves large deformation of the cable.
Improvement of brain angiographic images using 1.5t super conductive MRI unit of Imam Khomeini Hospital
"Takavar A,Rad Goodarzi M "
Acta Medica Iranica , 2002,
Abstract: Fue to the importance of selecting imaging parameters in magnetic resonance brain angiography, this study was carried out to choose optimum theoretical and experimental parameters for improving image controast and resolution and achieve shorter imaging time for practical reasons.A 1.5T super conductive magnet MRI with gradient power of 13 nT/m and Larmour frequency of 63 MHz with imaging coli of 30 cm was used.In this study, 5 healthy volunteers and 34 patients were the subjects of brain angiography. Flip angles of 15-20 degrees for peripheral brain vessels and 35-45 degrees for internal brain vessels were found to give higher contrast and better image resolution with a artifact. Using our optimum imaging parameters, (ie [TR/Te/FA/FOV] [40ms/7cm/20°/1mm 023cm], besides obtaining high quality angiography images, routine imaging time of 9-12 minutes was reduced to 7.3 mintues
Stabilization of a Rigid Body Payload with Multiple Cooperative Quadrotors
Farhad A. Goodarzi,Taeyoung Lee
Mathematics , 2015,
Abstract: This paper presents the full dynamics and control of arbitrary number of quadrotor unmanned aerial vehicles (UAV) transporting a rigid body. The rigid body is connected to the quadrotors via flexible cables where each flexible cable is modeled as a system of arbitrary number of serially connected links. It is shown that a coordinate-free form of equations of motion can be derived for the complete model without any simplicity assumptions that commonly appear in other literature, according to Lagrangian mechanics on a manifold. A geometric nonlinear controller is presented to transport the rigid body to a fixed desired position while aligning all of the links along the vertical direction. A rigorous mathematical stability proof is given and the desirable features of the proposed controller are illustrated by numerical examples and experimental results.
Dynamics and Control of Quadrotor UAVs Transporting a Rigid Body Connected via Flexible Cables
Farhad A. Goodarzi,Taeyoung Lee
Mathematics , 2015,
Abstract: This paper is focused on the dynamics and control of arbitrary number of quadrotor UAVs transporting a rigid body payload. The rigid body payload is connected to quadrotors via flexible cables where each flexible cable is modeled as a system of serially-connected links. It is shown that a coordinate-free form of equations of motion can be derived for arbitrary numbers of quadrotors and links according to Lagrangian mechanics on a manifold. A geometric nonlinear controller is presented to transport the rigid body to a fixed desired position while aligning all of the links along the vertical direction. Numerical results are provided to illustrate the desirable features of the proposed control system.
The Heterochromatic Barrier to DNA Double Strand Break Repair: How to Get the Entry Visa
Aaron A. Goodarzi,Penny A. Jeggo
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms130911844
Abstract: Over recent decades, a deep understanding of pathways that repair DNA double strand breaks (DSB) has been gained from biochemical, structural, biophysical and cellular studies. DNA non-homologous end-joining (NHEJ) and homologous recombination (HR) represent the two major DSB repair pathways, and both processes are now well understood. Recent work has demonstrated that the chromatin environment at a DSB significantly impacts upon DSB repair and that, moreover, dramatic modifications arise in the chromatin surrounding a DSB. Chromatin is broadly divided into open, transcriptionally active, euchromatin (EC) and highly compacted, transcriptionally inert, heterochromatin (HC), although these represent extremes of a spectrum. The HC superstructure restricts both DSB repair and damage response signaling. Moreover, DSBs within HC (HC-DSBs) are rapidly relocalized to the EC-HC interface. The damage response protein kinase, ataxia telangiectasia mutated (ATM), is required for HC-DSB repair but is dispensable for the relocalization of HC-DSBs. It has been proposed that ATM signaling enhances HC relaxation in the DSB vicinity and that this is a prerequisite for HC-DSB repair. Hence, ATM is essential for repair of HC-DSBs. Here, we discuss how HC impacts upon the response to DSBs and how ATM overcomes the barrier that HC poses to repair.
Accuracy of digital panoramic regarding interproximal caries detection
Goodarzi Pour D,Nejati S,Fotouhi A
Journal of Dental Medicine , 2011,
Abstract: "nBackground and Aims: Conventional radiological equipments in our country are going to be converted to digital system using computed radiology (CR) technology. If we know the accuracy of digital panoramic radiography for detection of small defects in tooth, it will be useful in cases with difficulty for taking the intraoral radiographs. The aim of this study was to evaluate sensitivity and specificity of digital panoramic radiography for detection of proximal caries compared with the bitewing radiography."nMaterials and Methods: One-hundred patients who had been ordered for taking both bitewing and panoramic radiography were included in this study. Panoramic and then bitewing radiographs were observed by a maxillofacial radiologist and interproximal caries were recorded. Sensitivity and specificity of digital panoramic radiography (CI=95%) was calculated compared with the bitewing radiography as a gold standard."nResults: This study showed that the values for sensitivity and specificity were 62.7% (CI 95%=57.7%-67.5%) and 91.0% (CI 95%=89.2%-92.5%), respectively."nConclusion: Sensitivity of digital panoramic is less than bitewing radiography even with processing before printing. Therefore, bitewing radiography is superior for detection of inter proximal caries.
Geometric Control of a Quadrotor UAV Transporting a Payload Connected via Flexible Cable
Farhad A. Goodarzi,Daewon Lee,Taeyoung Lee
Mathematics , 2014, DOI: 10.1007/s12555-014-0304-0
Abstract: We derived a coordinate-free form of equations of motion for a complete model of a quadrotor UAV with a payload which is connected via a flexible cable according to Lagrangian mechanics on a manifold. The flexible cable is modeled as a system of serially-connected links and has been considered in the full dynamic model. A geometric nonlinear control system is presented to exponentially stabilize the position of the quadrotor while aligning the links to the vertical direction below the quadrotor. Numerical simulation and experimental results are presented and a rigorous stability analysis is provided to confirm the accuracy of our derivations. These results will be particularly useful for aggressive load transportation that involves large deformation of the cable.
Geometric Stabilization of Quadrotor UAV with a Payload Connected by Flexible Cable
Farhad A. Goodarzi,Daewon Lee,Taeyoung Lee
Mathematics , 2013,
Abstract: Equations of motion and dynamics of a quadrotor transporting a load with a flexible cable modeled as a chain pendulum is obtained using Euler-Lagrange equations by taking variations on manifolds. An arbitrary number of links considered in a series models the flexible cable connecting the load to the quadrotor while the whole system can undergo complex motion in 3D. Geometric nonlinear control asymptotically stabilizes the load and cable bellow the quadrotor. A linearization about the equilibrium and the corresponding lyapunov stability analysis is provided. We produced numerical simulations and validated our work experimentally using a quadrotor UAV.
Geometric Adaptive Tracking Control of a Quadrotor UAV on SE(3) for Agile Maneuvers
Farhad A. Goodarzi,Daewon Lee,Taeyoung Lee
Mathematics , 2014, DOI: 10.1115/1.4030419
Abstract: This paper presents nonlinear tracking control systems for a quadrotor unmanned aerial vehicle under the influence of uncertainties. Assuming that there exist unstructured disturbances in the translational dynamics and the attitude dynamics, a geometric nonlinear adaptive controller is developed directly on the special Euclidean group. In particular, a new form of an adaptive control term is proposed to guarantee stability while compensating the effects of uncertainties in quadrotor dynamics. A rigorous mathematical stability proof is given. The desirable features are illustrated by numerical example and experimental results of aggressive maneuvers.
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