An investigation in crashworthiness evaluation of aircraft seat cushions at extreme ranges of temperature

Hamid Khademhosseini Beheshti,Hamid Lankarani 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.5

This paper obtains a Mathematical Dynamic Model (MADYMO) for occupant lumbar load evaluation under CFR Part 23 and 25 at extreme ranges of temperature. The validation of results is performed by full scale sled test results. Aircraft industries are using viscoelastic polyurethane foams as seat cushion. Visco-elastic foams bring not only more comfort to the passengers in long term sitting but it also maintains more safety during unpredicted crashes and hard landings. Aircraft seat cushions are exposed to varying temperature ranges during their life time. This fact has motivated aircraft industries to evaluate the seat cushion dynamic behavior at extreme ranges of temperatures in addition to what is mentioned in Federal Aviation Administration (FAA) Regulations at room temperature. This research provides a methodology based on simulation and modeling to eliminate, or at least, minimize the number of full scale dynamic sled tests defined by regulations for aircraft seats at extreme ranges of temperature.

Liver Cell Line Derived Conditioned Medium Enhances Myofibril Organization of Primary Rat Cardiomyocytes

김진석,Alireza Khademhosseini,황유식,정봉근,Alice Mira Chung 한국분자세포생물학회 2012 Molecules and cells Vol.34 No.2

Cardiomyocytes are the fundamental cells of the heart and play an important role in engineering of tissue constructs for regenerative medicine and drug discovery. Therefore, the development of culture conditions that can be used to generate functional cardiomyocytes to form cardiac tissue may be of great interest. In this study, isolated neonatal rat cardiomyocytes were cultured with several culture conditions in vitro and characterized for cell proliferation, myofibril organization, and cardiac functionality by assessing cell morphology, immunocytochemical staining, and time-lapse confocal scanning microscopy. When cardiomyocytes were cultured in liver cell line derived conditioned medium without exogenous growth factors and cytokines, the cell proliferation increased, cell morphology was highly elongated, and subsequent myofibril organization was highly developed. These developed myofibril organi-zation also showed high level of contractibility and synchronization, representing high functionality of cardiomyocytes. Interestingly, many of the known factors in hepatic conditioned medium, such as insulin-like growth factor II (IGFII), macrophage colony-stimulating factor (MCSF), leukemia inhibitory factor (LIF), did not show similar effects as the hepatic conditioned medium, suggesting the possibility of synergistic activity of the several soluble factors or the presence of unknown factors in hepatic conditioned medium. Finally, we demonstrated that our culture system could provide a potentially powerful tool for in vitro cardiac tissue organization and cardiac function study.

Disturbance Observer-based Trajectory Following Control of Robot Manipulators

Mohamadreza Homayounzade,Amir Khademhosseini 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1

Robotic manipulators are usually subject to different types of disturbances. If the effects of such disturbancesare not taken into account, it can lead to unsatisfactory tracking performance of the robot and may evendestabilize the robot control system. In this paper a novel nonlinear disturbance observer-based controller is designedfor robotic manipulators. Previous disturbance observer-based controllers which are designed for roboticsystems undergo the restricting assumption that the external disturbance is constant. In this paper a novel two-stageprocedure is proposed to design a disturbance observer that improves disturbance attenuation ability of current disturbanceobserver-based controllers. The proposed method can cope with non-constant disturbance. Furthermore,it is shown that even for the fast time varying disturbance, the controller achieves satisfactory tracking performance. The proposed controller guarantees semi-global asymptotic position and velocity tracking and moreover, removesrestrictions of previous studies on the number of degrees of freedom (DOFs), joint types, and manipulator configuration. The effectiveness of the proposed method is verified against different types of external disturbance appliedon the robot manipulator and the results are compared with the results of previous methods. Furthermore, the resultssupport the theoretical conclusions.

Impact noise radiated by collision of two spheres: Comparison between numerical simulations, experiments and analytical results

K. Mehraby,H. Khademhosseini Beheshti,M. Poursina 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Impact is very common source of noise in the industries. The impacts can be visible, such as forging, and can be invisible, such as impacts due to clearance of hinges. As a result of this generality, the control of impact noise needs more attention. Reduction of this tiresome noise needs enough perception about the impact. A study of this noise sources presents difficult problems both theoretically and experimentally. This is partly due to the many complex interconnected mechanical phenomena that occur and partly due to the fact that usual steady-state techniques of analysis cannot be applied. In such complex problems numerical techniques can help to acousticians. To gain some insight into this source of sound, in this paper collision of two steel spheres are studied with finite element method (FEM). Then the FEM results were compared with experiments to show authority of this numerical method to simulate impact noises. FEM results show that if the vibrational modes are excited by impact, the vibrational modes can be as effective as rigid body motion.

Direct Confinement of Individual Viruses within Polyethylene Glycol (PEG) Nanowells

Suh, K. Y.,Khademhosseini, A.,Jon, S.,Langer, R. American Chemical Society 2006 NANO LETTERS Vol.6 No.6

Micro/Nanometer‐Scale Fiber with Highly Ordered Structures by Mimicking the Spinning Process of Silkworm

Chae, Su‐,Kyoung,Kang, Edward,Khademhosseini, Ali,Lee, Sang‐,Hoon WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.22

<P><B>A new method for the microfluidic spinning of ultrathin fibers with highly ordered structures</B> is proposed by mimicking the spinning mechanism of silkworms. The self‐aggregation is driven by dipole–dipole attractions between polar polymers upon contact with a low‐polarity solvent to form fibers with nanostrands. The induction of Kelvin–Helmholtz instabilities at the dehydrating interface between two miscible fluids generates multi‐scale fibers in a single microchannel.</P>

Microfluidic fabrication of microengineered hydrogels and their application in tissue engineering.

Chung, Bong Geun,Lee, Kwang-Ho,Khademhosseini, Ali,Lee, Sang-Hoon Royal Society of Chemistry 2012 Lab on a chip Vol.12 No.1

<P>Microfluidic technologies are emerging as an enabling tool for various applications in tissue engineering and cell biology. One emerging use of microfluidic systems is the generation of shape-controlled hydrogels (i.e., microfibers, microparticles, and hydrogel building blocks) for various biological applications. Furthermore, the microfluidic fabrication of cell-laden hydrogels is of great benefit for creating artificial scaffolds. In this paper, we review the current development of microfluidic-based fabrication techniques for the creation of fibers, particles, and cell-laden hydrogels. We also highlight their emerging applications in tissue engineering and regenerative medicine.</P>

UV-assisted capillary force lithography for engineering biomimetic multiscale hierarchical structures: From lotus leaf to gecko foot hairs

Jeong, Hoon Eui,Kwak, Rhokyun,Khademhosseini, Ali,Suh, Kahp Y. The Royal Society of Chemistry 2009 Nanoscale Vol.1 No.3

<P>This feature article provides an overview of the recently developed two-step UV-assisted capillary force lithography and its application to fabricating well-defined micro/nanoscale hierarchical structures. This method utilizes an oxygen inhibition effect in the course of UV irradiation curing and a two-step moulding process, to form multiscale hierarchical or suspended nanobridge structures in a rapid and reproducible manner. After a brief description of the fabrication principles, several examples of the two-step UV-assisted moulding technique are presented. In addition, emerging applications of the multiscale hierarchical structures are briefly described.</P>

Cell-Based Dose Responses from Open-Well Microchambers

Hamon, Morgan,Jambovane, Sachin,Bradley, Lauren,Khademhosseini, Ali,Hong, Jong Wook American Chemical Society 2013 ANALYTICAL CHEMISTRY - Vol.85 No.10

<P>Cell-based assays play a critical role in discovery of new drugs and facilitating research in cancer, immunology, and stem cells. Conventionally, they are performed in Petri dishes, tubes, or well plates, using milliliters of reagents and thousands of cells to obtain one data point. Here, we are introducing a new platform to realize cell-based assay capable of increased throughput and greater sensitivity with a limited number of cells. We integrated an array of open-well microchambers into a gradient generation system. Consequently, cell-based dose responses were examined with a single device. We measured IC<SUB>50</SUB> values of three cytotoxic chemicals, Triton X-100, H<SUB>2</SUB>O<SUB>2</SUB>, and cadmium chloride, as model compounds. The present system is highly suitable for the discovery of new drugs and studying the effect of chemicals on cell viability or mortality with limited samples and cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2013/ancham.2013.85.issue-10/ac400743w/production/images/medium/ac-2013-00743w_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac400743w'>ACS Electronic Supporting Info</A></P>

Fabrication of non-biofouling polyethylene glycol micro- and nanochannels by ultraviolet-assisted irreversible sealing

Kim, Pilnam,Jeong, Hoon Eui,Khademhosseini, Ali,Suh, Kahp Y. Royal Society of Chemistry 2006 Lab on a chip Vol.6 No.11

<P>We present a simple and widely applicable method to fabricate micro- and nanochannels comprised entirely of crosslinked polyethylene glycol (PEG) by using UV-assisted irreversible sealing to bond partially crosslinked PEG surfaces. The method developed here can be used to form channels as small as ∼50 nm in diameter without using a sophisticated experimental setup. The manufactured channel is a homogeneous conduit made completely from non-biofouling PEG, exhibits robust sealing with minimal swelling and can be used without additional surface modification chemistries, thus significantly enhancing reliability and durability of microfluidic devices. Furthermore, we demonstrate simple analytical assays using PEG microchannels combined with patterned arrays of supported lipid bilayers (SLBs) to detect ligand (biotin)–receptor (streptavidin) interactions.</P> <P>Graphic Abstract</P><P>A simple and widely applicable method was developed to fabricate micro- and nanochannels comprised entirely of crosslinked polyethylene glycol (PEG) by using UV-assisted irreversible sealing to bond partially crosslinked PEG surfaces. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b610503c'> </P>