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991.
992.
Design and control of compliant tensegrity robots through simulation and hardware validation 总被引:1,自引:0,他引:1
Ken Caluwaerts Jérémie Despraz At?l I??en Andrew P. Sabelhaus Jonathan Bruce Benjamin Schrauwen Vytas SunSpiral 《Journal of the Royal Society Interface》2014,11(98)
To better understand the role of tensegrity structures in biological systems and their application to robotics, the Dynamic Tensegrity Robotics Lab at NASA Ames Research Center, Moffett Field, CA, USA, has developed and validated two software environments for the analysis, simulation and design of tensegrity robots. These tools, along with new control methodologies and the modular hardware components developed to validate them, are presented as a system for the design of actuated tensegrity structures. As evidenced from their appearance in many biological systems, tensegrity (‘tensile–integrity’) structures have unique physical properties that make them ideal for interaction with uncertain environments. Yet, these characteristics make design and control of bioinspired tensegrity robots extremely challenging. This work presents the progress our tools have made in tackling the design and control challenges of spherical tensegrity structures. We focus on this shape since it lends itself to rolling locomotion. The results of our analyses include multiple novel control approaches for mobility and terrain interaction of spherical tensegrity structures that have been tested in simulation. A hardware prototype of a spherical six-bar tensegrity, the Reservoir Compliant Tensegrity Robot, is used to empirically validate the accuracy of simulation. 相似文献
993.
Jorn A. Cheney Nicolai Konow Andrew Bearnot Sharon M. Swartz 《Journal of the Royal Society Interface》2015,12(106)
Bats fly using a thin wing membrane composed of compliant, anisotropic skin. Wing membrane skin deforms dramatically as bats fly, and its three-dimensional configurations depend, in large part, on the mechanical behaviour of the tissue. Large, macroscopic elastin fibres are an unusual mechanical element found in the skin of bat wings. We characterize the fibre orientation and demonstrate that elastin fibres are responsible for the distinctive wrinkles in the surrounding membrane matrix. Uniaxial mechanical testing of the wing membrane, both parallel and perpendicular to elastin fibres, is used to distinguish the contribution of elastin and the surrounding matrix to the overall membrane mechanical behaviour. We find that the matrix is isotropic within the plane of the membrane and responsible for bearing load at high stress; elastin fibres are responsible for membrane anisotropy and only contribute substantially to load bearing at very low stress. The architecture of elastin fibres provides the extreme extensibility and self-folding/self-packing of the wing membrane skin. We relate these findings to flight with membrane wings and discuss the aeromechanical significance of elastin fibre pre-stress, membrane excess length, and how these parameters may aid bats in resisting gusts and preventing membrane flutter. 相似文献
994.
A Multifunctional Nanoplatform for Imaging,Radiotherapy, and the Prediction of Therapeutic Response
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Casey McQuade Ajlan Al Zaki Yaanik Desai Michael Vido Timothy Sakhuja Zhiliang Cheng Robert J. Hickey Daniel Joh So‐Jung Park Gary Kao Jay F. Dorsey Andrew Tsourkas 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(7):834-843
Gold nanoparticles have garnered interest as both radiosensitzers and computed tomography (CT) contrast agents. However, the extremely high concentrations of gold required to generate CT contrast is far beyond that needed for meaningful radiosensitization, which limits their use as combined therapeutic–diagnostic (theranostic) agents. To establish a theranostic nanoplatform with well‐aligned radiotherapeutic and diagnostic properties for better integration into standard radiation therapy practice, a gold‐ and superparamagnetic iron oxide nanoparticle (SPION)‐loaded micelle (GSM) is developed. Intravenous injection of GSMs into tumor‐bearing mice led to selective tumoral accumulation, enabling magnetic resonance (MR) imaging of tumor margins. Subsequent irradiation leads to a 90‐day survival of 71% in GSM‐treated mice, compared with 25% for irradiation‐only mice. Furthermore, measurements of the GSM‐enhanced MR contrast are highly predictive of tumor response. Therefore, GSMs may not only guide and enhance the efficacy of radiation therapy, but may allow patients to be managed more effectively. 相似文献
995.
Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer
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Steven Lukman Andrew J. Musser Kai Chen Stavros Athanasopoulos Chaw K. Yong Zebing Zeng Qun Ye Chunyan Chi Justin M. Hodgkiss Jishan Wu Richard H. Friend Neil C. Greenham 《Advanced functional materials》2015,25(34):5452-5461
Fast and highly efficient intramolecular singlet exciton fission in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units is reported. Fission to triplet excitons from this ground state geometry occurs within 1 ps in isolated molecules in solution and dispersed solid matrices. The process exhibits a sensitivity to environmental polarity and competes with geometric relaxation in the singlet state, while subsequent triplet decay is strongly dependent on conformational freedom. The near orthogonal arrangement of the pentacene units is unlike any structure currently proposed for efficient singlet exciton fission and may lead to new molecular design rules. 相似文献
996.
Red Blood Cell Membrane as a Biomimetic Nanocoating for Prolonged Circulation Time and Reduced Accelerated Blood Clearance
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Lang Rao Lin‐Lin Bu Jun‐Hua Xu Bo Cai Guang‐Tao Yu Xiaolei Yu Zhaobo He Qinqin Huang Andrew Li Shi‐Shang Guo Wen‐Feng Zhang Wei Liu Zhi‐Jun Sun Hao Wang Tza‐Huei Wang Xing‐Zhong Zhao 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(46):6225-6236
For decades, poly(ethylene glycol) (PEG) has been widely incorporated into nanoparticles for evading immune clearance and improving the systematic circulation time. However, recent studies have reported a phenomenon known as “accelerated blood clearance (ABC)” where a second dose of PEGylated nanomaterials is rapidly cleared when given several days after the first dose. Herein, we demonstrate that natural red blood cell (RBC) membrane is a superior alternative to PEG. Biomimetic RBC membrane‐coated Fe3O4 nanoparticles (Fe3O4@RBC NPs) rely on CD47, which is a “don't eat me” marker on the RBC surface, to escape immune clearance through interactions with the signal regulatory protein‐alpha (SIRP‐α) receptor. Fe3O4@RBC NPs exhibit extended circulation time and show little change between the first and second doses, with no ABC suffered. In addition, the administration of Fe3O4@RBC NPs does not elicit immune responses on neither the cellular level (myeloid‐derived suppressor cells (MDSCs)) nor the humoral level (immunoglobulin M and G (IgM and IgG)). Finally, the in vivo toxicity of these cell membrane‐camouflaged nanoparticles is systematically investigated by blood biochemistry, hematology testing, and histology analysis. These findings are significant advancements toward solving the long‐existing clinical challenges of developing biomaterials that are able to resist both immune response and rapid clearance. 相似文献
997.
998.
Hui-Chi Chen Andrew J. Pinkerton Lin Li 《The International Journal of Advanced Manufacturing Technology》2011,52(9-12):977-987
Challenges in dissimilar materials welding are the differences of physical and chemical properties between welding materials and the formation of intermetallic brittle phases resulting in the degradation of mechanical properties of welds. However, dissimilar materials welding is increasingly demanded from the industry as it can effectively reduce material costs and improve the design. In aerospace applications, Ti-6Al-4V titanium alloy and Inconel 718 nickel alloy have been widely used because of their superior corrosion resistance and mechanical properties. In this study, a single-mode continuous-wave fibre laser was used in butt welding of Ti-6Al-4V to Inconel 718. Investigations including metallurgical and mechanical examinations were carried out by means of varying processing parameters, such as laser power, welding speed and the laser beam offset position from the interface of the metals. Simple analytical modelling analysis was undertaken to explain the phenomena that occurred in this process. Results showed that the formation of intermetallic brittle phases and welding defects could be effectively restricted at welding conditions produced by the combination of higher laser power, higher welding speed and shifting the laser beam from the interface to the Inconel 718 alloy side. The amount of heat input and position of laser beam to improve the Ti-6Al-4V/Inconel 718 weld quality are suggested. 相似文献
999.
Imported liquefied natural gas can provide needed supplements to diminishing domestic gas supplies as well as being a convenient means for the storage and transportation of natural gas. LNG vessels and facilities are, however, costly and present the risk of potentially large accidents. We describe these risks and the impacts of LNG operations, summarize the safety issues, and make several policy recommendations for the responsible use of this premium fossil fuel. 相似文献
1000.
Natural gas transmission systems often involve a pressure reduction process that does not make use of the mechanical exergy available in the gas. A moderate fraction of this work potential can be extracted using turbo-machinery. This paper quantifies the energy that can be extracted from various pressure reduction facilities using an expander coupled to an electric generator. Produced electricity can either be routed back into the electric distribution grid or used to produce small amounts of hydrogen. A problem with this process is the variable nature of the gas flow rate entering the facility. For the pressure reduction station data used in this study, the gas flow rate may drop to below one quarter of the peak, reducing the efficiency and production rates of the coupled components. A model has been created to analyze these seasonal variations and to produce generalized functions that allow the hydrogen production potential of any pressure reduction facility to be approximated. If the coupled technologies operate at their assumed peak efficiencies, then electricity can be extracted from the pressure reduction with 75% exergetic efficiency and hydrogen can be produced with 45% exergetic efficiency. 相似文献