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Dumitru I. Caruntu

Bio: Dumitru I. Caruntu is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Natural frequency & Resonator. The author has an hindex of 15, co-authored 68 publications receiving 761 citations. Previous affiliations of Dumitru I. Caruntu include Politehnica University of Bucharest & University of Toledo.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a detailed explanation of the fiber formation process is presented using high speed photography to capture the jet initiation process at the orifice and to track the trajectories of the resulting jets.
Abstract: A newly developed method of producing nanofibers, called forcespinning, has proven to be a viable alternative to mass produce nanofibers. Unlike electrospinning, the most common method currently being employed (which draws fibers through the use of electrostatic force), forcespinning utilizes centrifugal forces which allow for a host of new materials to be processed into nanofibers (given that electric fields are not required) while also providing a significant increase in yield and ease of production. This work presents a detailed explanation of the fiber formation process. The study is conducted using high speed photography to capture the jet initiation process at the orifice and to track the trajectories of the resulting jets. The effects that influential controllable parameters have on the fiber trajectories and final fiber diameters are presented. The forcespinning controllable parameters include the spinneret angular velocity and aspect ratio, orifice radius and orientation, fluid viscoelasticity and surface tension, fluid fill level, solvent evaporation rate, temperature, and distance of spinneret orifice to collector.

226 citations

Journal ArticleDOI
TL;DR: An anatomical dynamic model consisting of three body segments, femur, tibia and patella, has been developed in order to determine the three-dimensional dynamic response of the human knee.
Abstract: An anatomical dynamic model consisting of three body segments, femur, tibia and patella, has been developed in order to determine the three-dimensional dynamic response of the human knee. Deformable contact was allowed at all articular surfaces, which were mathematically represented using Coons' bicubic surface patches. Nonlinear elastic springs were used to model all ligamentous structures. Two joint coordinate systems were employed to describe the six-degrees-of-freedom tibio-femoral (TF) and patello-femoral (PF) joint motions using twelve kinematic parameters. Two versions of the model were developed to account for wrapping and nonwrapping of the quadriceps tendon around the femur. Model equations consist of twelve nonlinear second-order ordinary differential equations coupled with nonlinear algebraic constraint equations resulting in a Differential-Algebraic Equations (DAE) system that was solved using the Differential/Algebraic System Solver (DASSL) developed at Lawrence Livermore National Laboratory. Model calculations were performed to simulate the knee extension exercise by applying non-linear forcing functions to the quadriceps tendon. Under the conditions tested, both "screw home mechanism" and patellar flexion lagging were predicted. Throughout the entire range of motion, the medial component of the TF contact force was found to be larger than the lateral one while the lateral component of the PF contact force was found to be larger than the medial one. The anterior and posterior fibers of both anterior and posterior cruciate ligaments, ACL and PCL, respectively, had opposite force patterns: the posterior fibers were most taut at full extension while the anterior fibers were most taut near 90 degrees of flexion. The ACL was found to carry a larger total force than the PCL at full extension, while the PCL carried a larger total force than the ACL in the range of 75 degrees to 90 degrees of flexion.

74 citations

Journal ArticleDOI
TL;DR: In this paper, a comparison between the Reduced Order Model (ROM) method and the Method of Multiple Scales (MMS) for both small and large amplitudes is reported for parametric resonance of microelectromechanical cantilever resonators under soft damping, and soft alternating current (AC) electrostatic actuation to include fringing effect.
Abstract: This paper deals with parametric resonance of microelectromechanical (MEMS) cantilever resonators under soft damping, and soft alternating current (AC) electrostatic actuation to include fringing effect. A comparison between the Reduced Order Model (ROM) method and the Method of Multiple Scales (MMS) for both small and large amplitudes is reported. The actuation is parametric non-linear. It includes non-linear terms with periodic coefficients. The AC frequency is near resonator׳s natural frequency. The amplitude frequency response is investigated using ROM. Damping, voltage, and fringe effects on the response are also reported. It is showed that five terms ROM accurately predicts the behavior of the resonator at all amplitudes, while MMS is accurate only for small amplitudes.

52 citations

Journal ArticleDOI
TL;DR: In this paper, the authors considered free transverse vibrations of nonuniform homogeneous beams and derived their fourth order differential equations of transverse vibration into a pair of second-order differential equations, leading to general solutions in terms of hypergeometric functions.

51 citations

Journal ArticleDOI
TL;DR: In this article, Jacobi classes of beams and axisymmetrical circular plates whose boundary value problems can be reduced to an eigenvalue singular problem (singularities occur at both ends) of orthogonal polynomials are reported.

46 citations


Cited by
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01 Jan 2016
TL;DR: Biomechanics and motor control of human movement is downloaded so that people can enjoy a good book with a cup of tea in the afternoon instead of juggling with some malicious virus inside their laptop.
Abstract: Thank you very much for downloading biomechanics and motor control of human movement. Maybe you have knowledge that, people have search hundreds times for their favorite books like this biomechanics and motor control of human movement, but end up in infectious downloads. Rather than enjoying a good book with a cup of tea in the afternoon, instead they juggled with some malicious virus inside their laptop.

1,689 citations

Book ChapterDOI
31 Dec 1939

811 citations

Book ChapterDOI
31 Dec 1939

277 citations