The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon topology.Detailed deformation modes along two orthogonal directions are examined,where a parametric...The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon topology.Detailed deformation modes along two orthogonal directions are examined,where a parametric study of the effect of impact velocity and cell wall aspect ratio is performed.An analytical formula of the dynamic crushing strength is then deduced based on the periodic collapse mechanism of cell structures.Comparisons with the finite element results validate the effectiveness of the proposed analytical method.Numerical results also reveal higher plateau stress of re-entrant honeycomb over conventional hexagon topology,implying better energy absorption properties.The underlying physical understanding of the results is emphasized,where the auxetic effect（negative Poisson＇s ratio） induced in the re-entrant topology is believed to be responsible for this superior impact resistance.展开更多
The current situation of medical staff＇s awareness about high alert medication was investigated in order to promote safe medication and standardized management of the high alert medication in China. Twenty questions ...The current situation of medical staff＇s awareness about high alert medication was investigated in order to promote safe medication and standardized management of the high alert medication in China. Twenty questions were designed concerning elementary knowledge of high alert medications, storage management, medication issues and risks. In order to understand the knowledge level and education status of high alert medication, a convenient survey was conducted among 300 medical staffs in Tianjin. Medical staff＇s average score of high alert medication knowledge was 12.43±0.27, and the average scores of elementary knowledge of high alert medication, storage management, medication issues and risks were 3.38±0.11, 2.46±0.14, 3.17±0.11 and 3.41±0.12 respectively. Occupation（F=4.86, P=0.003）, education background（F=5.57, P=0.019） and professional titles（F=13.44, P≤0.001） contributed to the high alert medications knowledge scores. Currently, the most important channel to obtain high alert medication knowledge was hospital files or administrative rules, and clinical pharmacist seminars were the most popular education form. It was suggested that the high alert medication knowledge level of the medical staff needs to increase, and it might benefit from targeted, systematic and diverse training to the medical staff working in the different circulation nodes of the medications. Further research to develop and validate the instrument is needed.展开更多
Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from ...Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries.This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified.Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.展开更多
Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar（ISAR）.By photonic generation and de-chirping ...Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar（ISAR）.By photonic generation and de-chirping of broadband linear frequency modulation signals,the radar can achieve a high range resolution thanks to the large instantaneous bandwidth（8 GHz at the K band）,as well as real-time ISAR imaging using low-speed analog-to-digital conversion（25 MSa/s）.A small-size unmanned aerial vehicle is employed as the noncooperative target,and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs.The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps.These results validate that the photonics-based radar is feasible in practical real-time and highresolution ISAR imaging applications.展开更多
The problem of designing passive fault-tolerant flight controller is addressed when the normal and faulty cases are prescribed. First of all, the considered fault and fault-free cases are formed by polytopes. As consi...The problem of designing passive fault-tolerant flight controller is addressed when the normal and faulty cases are prescribed. First of all, the considered fault and fault-free cases are formed by polytopes. As considering that the safety of a post-fault system is directly related to the maximum values of physical variables in the system, peak-to-peak gain is selected to represent the relationships among the amplitudes of actuator outputs, system outputs, and reference commands. Based on the parameter dependent Lyapunov and slack methods, the passive fault-tolerant flight controllers in the absence/presence of system uncertainty for actuator failure cases are designed, respectively. Case studies of an airplane under actuator failures are carried out to validate the effectiveness of the proposed approach展开更多
We propose and experimentally demonstrate an adaptive multiple-input multiple-output（MIMO） mode switching scheme for an indoor visible light communication system combined with orthogonal frequency division multiplex...We propose and experimentally demonstrate an adaptive multiple-input multiple-output（MIMO） mode switching scheme for an indoor visible light communication system combined with orthogonal frequency division multiplexing modulation.Only requiring 1 bit feedback from the receiver,the MIMO mode at the transmitter switches between spatial multiplexing and transmit diversity adapting to the channel correlation.In such a way,we can take advantage of both spatial multiplexing and transmit diversity,where the spatial multiplexing benefits for its multiplexing gain in the low channel correlation environment,and the transmit diversity is robust to high channel correlation.Experimental results validate the performance improvement over the pure spatial multiplexing or transmit diversity system.With the increasing of the channel correlation,the measured bit error rates of the proposed system are below the 7% pre-forward error correction（pre-FEC） limit of 3.8 × 10-（-3）when the transmitted data rate is 50 Mb/s,and below the 20% pre-FEC threshold of 5.0 × 10-（-2） when the transmitted data rate is raised up to 100 Mb/s.展开更多
The 3-D hydrodynamics of shear thinning fluids in a stirred tank with an anchor impeller were numerically simulated.By using a computational fluid dynamics code（CFX 13.0）,the obtained results give a good prediction ...The 3-D hydrodynamics of shear thinning fluids in a stirred tank with an anchor impeller were numerically simulated.By using a computational fluid dynamics code（CFX 13.0）,the obtained results give a good prediction of the hydrodynamics such as the velocity fields and cavern size.The multiple reference frames（MRF） technique was employed to model the rotation of the impellers.The rheology of the fluid was approximated using the Ostwald model.To validate the CFD model,some predicted results were compared with the experimental data and a satisfactory agreement was found.The effects of impeller speed,fluid rheology,and some design parameters on the flow pattern,cavern size and power consumption were explored.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11372252 and 11402035)
文摘The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon topology.Detailed deformation modes along two orthogonal directions are examined,where a parametric study of the effect of impact velocity and cell wall aspect ratio is performed.An analytical formula of the dynamic crushing strength is then deduced based on the periodic collapse mechanism of cell structures.Comparisons with the finite element results validate the effectiveness of the proposed analytical method.Numerical results also reveal higher plateau stress of re-entrant honeycomb over conventional hexagon topology,implying better energy absorption properties.The underlying physical understanding of the results is emphasized,where the auxetic effect（negative Poisson＇s ratio） induced in the re-entrant topology is believed to be responsible for this superior impact resistance.
基金supported by grants from Basic Scientific Research Business Expenses Foundation of Huazhong University of Science and Technology,China(No2014QN136)Natural Science Foundation of Hube Province,China(No.2014CFB955)
文摘The current situation of medical staff＇s awareness about high alert medication was investigated in order to promote safe medication and standardized management of the high alert medication in China. Twenty questions were designed concerning elementary knowledge of high alert medications, storage management, medication issues and risks. In order to understand the knowledge level and education status of high alert medication, a convenient survey was conducted among 300 medical staffs in Tianjin. Medical staff＇s average score of high alert medication knowledge was 12.43±0.27, and the average scores of elementary knowledge of high alert medication, storage management, medication issues and risks were 3.38±0.11, 2.46±0.14, 3.17±0.11 and 3.41±0.12 respectively. Occupation（F=4.86, P=0.003）, education background（F=5.57, P=0.019） and professional titles（F=13.44, P≤0.001） contributed to the high alert medications knowledge scores. Currently, the most important channel to obtain high alert medication knowledge was hospital files or administrative rules, and clinical pharmacist seminars were the most popular education form. It was suggested that the high alert medication knowledge level of the medical staff needs to increase, and it might benefit from targeted, systematic and diverse training to the medical staff working in the different circulation nodes of the medications. Further research to develop and validate the instrument is needed.
基金supported by the Fundamental Research Grant Scheme FRGS/1/2014/TK03/QUEST/03/1 from the Ministry of Education(MoE)Malaysia
文摘Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries.This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified.Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.
基金supported in part by the National Natural Science Foundation of China(Nos.61401201 and61422108)the Aviation Science Foundation of China(No.2015ZC52024)the Open Fund of Science and Technology on Monolithic Integrated Circuits and Modules Laboratory(No.20150C1404)
文摘Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar（ISAR）.By photonic generation and de-chirping of broadband linear frequency modulation signals,the radar can achieve a high range resolution thanks to the large instantaneous bandwidth（8 GHz at the K band）,as well as real-time ISAR imaging using low-speed analog-to-digital conversion（25 MSa/s）.A small-size unmanned aerial vehicle is employed as the noncooperative target,and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs.The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps.These results validate that the photonics-based radar is feasible in practical real-time and highresolution ISAR imaging applications.
基金financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC)through Discovery Grant and Engage Grant for the work reported in this paper
文摘The problem of designing passive fault-tolerant flight controller is addressed when the normal and faulty cases are prescribed. First of all, the considered fault and fault-free cases are formed by polytopes. As considering that the safety of a post-fault system is directly related to the maximum values of physical variables in the system, peak-to-peak gain is selected to represent the relationships among the amplitudes of actuator outputs, system outputs, and reference commands. Based on the parameter dependent Lyapunov and slack methods, the passive fault-tolerant flight controllers in the absence/presence of system uncertainty for actuator failure cases are designed, respectively. Case studies of an airplane under actuator failures are carried out to validate the effectiveness of the proposed approach
基金supported by the National Natural Science Foundation of China under Grant No.61501296
文摘We propose and experimentally demonstrate an adaptive multiple-input multiple-output（MIMO） mode switching scheme for an indoor visible light communication system combined with orthogonal frequency division multiplexing modulation.Only requiring 1 bit feedback from the receiver,the MIMO mode at the transmitter switches between spatial multiplexing and transmit diversity adapting to the channel correlation.In such a way,we can take advantage of both spatial multiplexing and transmit diversity,where the spatial multiplexing benefits for its multiplexing gain in the low channel correlation environment,and the transmit diversity is robust to high channel correlation.Experimental results validate the performance improvement over the pure spatial multiplexing or transmit diversity system.With the increasing of the channel correlation,the measured bit error rates of the proposed system are below the 7% pre-forward error correction（pre-FEC） limit of 3.8 × 10-（-3）when the transmitted data rate is 50 Mb/s,and below the 20% pre-FEC threshold of 5.0 × 10-（-2） when the transmitted data rate is raised up to 100 Mb/s.
文摘The 3-D hydrodynamics of shear thinning fluids in a stirred tank with an anchor impeller were numerically simulated.By using a computational fluid dynamics code（CFX 13.0）,the obtained results give a good prediction of the hydrodynamics such as the velocity fields and cavern size.The multiple reference frames（MRF） technique was employed to model the rotation of the impellers.The rheology of the fluid was approximated using the Ostwald model.To validate the CFD model,some predicted results were compared with the experimental data and a satisfactory agreement was found.The effects of impeller speed,fluid rheology,and some design parameters on the flow pattern,cavern size and power consumption were explored.
