Plasma control of forebody asymmetric vortices is mostly achieved by means of dielectric barrier discharge(DBD)plasma actuators. However, DBD actuators suffer from some disadvantages such as a weak induced body force,...Plasma control of forebody asymmetric vortices is mostly achieved by means of dielectric barrier discharge(DBD)plasma actuators. However, DBD actuators suffer from some disadvantages such as a weak induced body force, a singledirection induced jet, and an unclear control mechanism. We carry out wind tunnel experiments involving the forebody vortex control of a slender body at high angles of attack using an innovative extended DBD actuator, which has a stronger capacity to induce an electric wind than a DBD actuator. Through synchronous measurements of the pressure distribution and particle image velocimetry(PIV), the spatiotemporal evolution of the dynamic interactions between plasma-actuationinduced vortices and forebody asymmetric vortices is analyzed. The influence of plasma discharge on the boundary layer separation around a slender body and the spatial topological structures of asymmetric vortices are further surveyed, as the optimized actuation parameters. Extended DBD actuators are found to be more capable of controlling asymmetric vortices than DBD actuators, and a linear proportionality of the sectional lateral force versus the duty ratio is achieved.There exists an optimal normalized reduced frequency( f+= 2π fpd/U∞= 2.39) for asymmetric vortex control under the present experimental conditions. The research results can provide technical guidance for the control and reuse of forebody asymmetric vortices.展开更多
The design of a universal waveform generator derived from displaying driving applications using floating power and Miller integrator circuit is introduced first. Then, the feasibility of driving ultrasound transducers...The design of a universal waveform generator derived from displaying driving applications using floating power and Miller integrator circuit is introduced first. Then, the feasibility of driving ultrasound transducers is verified by the test of the circuit and compared with other specific design of pulse generator for ultrasound driving purpose.展开更多
This paper reviews the recent progress on bionic microelectromechanical systems(MEMS)used for touching and hearing sensations,focusing on the following three types of devices:MEMS tactile sensors,MEMS directional micr...This paper reviews the recent progress on bionic microelectromechanical systems(MEMS)used for touching and hearing sensations,focusing on the following three types of devices:MEMS tactile sensors,MEMS directional microphones,and MEMS vector hydrophones.After reviewing the electromechanical coupling principles,design,and performance of these MEMS devices,the authors conclude that it is vital for future research efforts in bionic MEMS to focus more on microfabrication technologies.The development of robust microfabrication flows is the basis to implement hybrid electromechanical coupling principles based on novel functional materials.High-quality polymeric micromachining technologies can also significantly enhance the potential of existing bionic MEMS designs for more practical applications.展开更多
BACKGROUND Spinal deformities in Ehlers-Danlos syndrome(EDS; type VI) are generally progressive and severe. Surgical treatment has been described for kyphoscoliosis in the thoracolumbar spine. However, there are few s...BACKGROUND Spinal deformities in Ehlers-Danlos syndrome(EDS; type VI) are generally progressive and severe. Surgical treatment has been described for kyphoscoliosis in the thoracolumbar spine. However, there are few studies describing the consequences of an anterior approach in cervical kyphosis. An anterior approach may not be able to fully decompress the spinal canal and restore the normal curvature of the cervical spine. Therefore, the anterior approach for cervical kyphosis in young children is hard. We describe the first case in an EDS girl with cervical kyphosis who received satisfactory anterior cervical corpectomy decompression and fusion.CASE SUMMARY The chief complaints of a 16-year-old girl with EDS were double upper limb weakness for 7 years and double lower limb walking instability for 2 years.Moreover, the imaging results revealed that the degree of kyphosis from cervical vertebra 2 to 4 accompanying with spinal cord compression was 30°. An anterior cervical corpectomy involving cervical vertebra 3 and a titanium mesh implant were performed with internal fixation. The results at 3 mo after surgery demonstrated that the anterior fusion was solid, and the kyphosis of the cervical spine was corrected. Additionally, the power of all four extremities was significantly improved.CONCLUSION The incidence rate of cervical kyphosis in EDS is rare. The surgical treatment for these patients, especially an anterior approach, is challenging. Therefore, to develop safer and more effective strategies to treat cervical kyphosis in EDS,there is still much work to do.展开更多
We present a novel stackable luminescent device integrating a blue light emitting diode(LED)with a red organic LED(OLED)in series.The anode of the OLED is connected with the cathode of the LED through a via in the ins...We present a novel stackable luminescent device integrating a blue light emitting diode(LED)with a red organic LED(OLED)in series.The anode of the OLED is connected with the cathode of the LED through a via in the insulation layer on the LED.The LED–OLED hybrid device is electroluminescent and two electroluminescence(EL)peaks(the blue peak around 454 nm and the red peak around 610 nm)are observed clearly.The effect of the indium tin oxide(ITO)layer on the device performance is analyzed.Compared with the individual LED and OLED,their combination shows great potential applications in the field of white lighting,plant lighting,and display.展开更多
In this paper,size effects on optical performance of blue light-emitting diodes(LEDs)are investigated.The essential physical mechanism is studied by fabricating LEDs with various sizes of the active area and testing o...In this paper,size effects on optical performance of blue light-emitting diodes(LEDs)are investigated.The essential physical mechanism is studied by fabricating LEDs with various sizes of the active area and testing optical characteristics.It is found that micro-LEDs have better light extracting efficiency and thermal dissipation compared with broad-area LEDs,which is likely due to the small ratio of perimeter and active area.Furthermore,micro-LEDs are more beneficial for displays due to the stable wavelength under the low pulse width modulation(PWM)current density.展开更多
Plasma flow control is a new type of active flow control approach based on plasma pneumatic actuation.Dielectric barrier discharge(DBD) actuators have become a focus of international aerodynamic research.However,the p...Plasma flow control is a new type of active flow control approach based on plasma pneumatic actuation.Dielectric barrier discharge(DBD) actuators have become a focus of international aerodynamic research.However,the practical applications of typical DBDs are largely restricted due to their limited discharge area and low relative-induced velocity.The further improvement of performance will be beneficial for engineering applications.In this paper,high-speed schlieren and high-speed particle image velocimetry(PIV) are employed to study the flow field induced by three kinds of plasma actuations in a static atmosphere,and the differences in induced flow field structure among typical DBD,extended DBD(EX-DBD),and tri-electrode sliding discharge(TED) are compared.The analyzing of the dynamic evolution of the maximum horizontal velocity over time,the velocity profile at a fixed horizontal position,and the momentum and body force in a control volume reveals that the induced velocity peak value and profile velocity height of EX-DBD are higher than those of the other two types of actuation,suggesting that EX-DBD actuation has the strongest temporal aerodynamic effect among the three types of actuations.The TED actuation not only can enlarge the plasma extension but also has the longest duration in the entire pulsed period and the greatest influence on the height and width of the airflow near the wall surface.Thus,the TED actuation has the ability to continuously influencing a larger three-dimensional space above the surface of the nlasma actuator.展开更多
基金National Natural Science Foundation of China(Grant Nos.51607188 and 61971345)the Foundation for Key Laboratories of National Defense Science and Technology,China(Grant No.614220202011801)+1 种基金the Natural Science Basic Research Program of Shaanxi Province of China(Grant No.2019JM-393)Xi’an Municipal Science and Technology Project of China(Grant No.201805037YD15CG21(28)).
文摘Plasma control of forebody asymmetric vortices is mostly achieved by means of dielectric barrier discharge(DBD)plasma actuators. However, DBD actuators suffer from some disadvantages such as a weak induced body force, a singledirection induced jet, and an unclear control mechanism. We carry out wind tunnel experiments involving the forebody vortex control of a slender body at high angles of attack using an innovative extended DBD actuator, which has a stronger capacity to induce an electric wind than a DBD actuator. Through synchronous measurements of the pressure distribution and particle image velocimetry(PIV), the spatiotemporal evolution of the dynamic interactions between plasma-actuationinduced vortices and forebody asymmetric vortices is analyzed. The influence of plasma discharge on the boundary layer separation around a slender body and the spatial topological structures of asymmetric vortices are further surveyed, as the optimized actuation parameters. Extended DBD actuators are found to be more capable of controlling asymmetric vortices than DBD actuators, and a linear proportionality of the sectional lateral force versus the duty ratio is achieved.There exists an optimal normalized reduced frequency( f+= 2π fpd/U∞= 2.39) for asymmetric vortex control under the present experimental conditions. The research results can provide technical guidance for the control and reuse of forebody asymmetric vortices.
文摘The design of a universal waveform generator derived from displaying driving applications using floating power and Miller integrator circuit is introduced first. Then, the feasibility of driving ultrasound transducers is verified by the test of the circuit and compared with other specific design of pulse generator for ultrasound driving purpose.
文摘This paper reviews the recent progress on bionic microelectromechanical systems(MEMS)used for touching and hearing sensations,focusing on the following three types of devices:MEMS tactile sensors,MEMS directional microphones,and MEMS vector hydrophones.After reviewing the electromechanical coupling principles,design,and performance of these MEMS devices,the authors conclude that it is vital for future research efforts in bionic MEMS to focus more on microfabrication technologies.The development of robust microfabrication flows is the basis to implement hybrid electromechanical coupling principles based on novel functional materials.High-quality polymeric micromachining technologies can also significantly enhance the potential of existing bionic MEMS designs for more practical applications.
文摘BACKGROUND Spinal deformities in Ehlers-Danlos syndrome(EDS; type VI) are generally progressive and severe. Surgical treatment has been described for kyphoscoliosis in the thoracolumbar spine. However, there are few studies describing the consequences of an anterior approach in cervical kyphosis. An anterior approach may not be able to fully decompress the spinal canal and restore the normal curvature of the cervical spine. Therefore, the anterior approach for cervical kyphosis in young children is hard. We describe the first case in an EDS girl with cervical kyphosis who received satisfactory anterior cervical corpectomy decompression and fusion.CASE SUMMARY The chief complaints of a 16-year-old girl with EDS were double upper limb weakness for 7 years and double lower limb walking instability for 2 years.Moreover, the imaging results revealed that the degree of kyphosis from cervical vertebra 2 to 4 accompanying with spinal cord compression was 30°. An anterior cervical corpectomy involving cervical vertebra 3 and a titanium mesh implant were performed with internal fixation. The results at 3 mo after surgery demonstrated that the anterior fusion was solid, and the kyphosis of the cervical spine was corrected. Additionally, the power of all four extremities was significantly improved.CONCLUSION The incidence rate of cervical kyphosis in EDS is rare. The surgical treatment for these patients, especially an anterior approach, is challenging. Therefore, to develop safer and more effective strategies to treat cervical kyphosis in EDS,there is still much work to do.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0404800)。
文摘We present a novel stackable luminescent device integrating a blue light emitting diode(LED)with a red organic LED(OLED)in series.The anode of the OLED is connected with the cathode of the LED through a via in the insulation layer on the LED.The LED–OLED hybrid device is electroluminescent and two electroluminescence(EL)peaks(the blue peak around 454 nm and the red peak around 610 nm)are observed clearly.The effect of the indium tin oxide(ITO)layer on the device performance is analyzed.Compared with the individual LED and OLED,their combination shows great potential applications in the field of white lighting,plant lighting,and display.
基金supported by National Key Research and Development Program of China (No. 2017YFB0404800)
文摘In this paper,size effects on optical performance of blue light-emitting diodes(LEDs)are investigated.The essential physical mechanism is studied by fabricating LEDs with various sizes of the active area and testing optical characteristics.It is found that micro-LEDs have better light extracting efficiency and thermal dissipation compared with broad-area LEDs,which is likely due to the small ratio of perimeter and active area.Furthermore,micro-LEDs are more beneficial for displays due to the stable wavelength under the low pulse width modulation(PWM)current density.
基金Project supported by the National Natural Science Foundation of China(Grant No.51607188)the Foundation for Key Laboratories of National Defense Science and Technology,China(Grant No.614220202011801)+2 种基金the Shaanxi Provincial Natural Science Basic Research Program,China(Grant No.2019JM-393)the Shaanxi Provincial Key Industry Innovation,Chain(Grant No.2017ZDCXL-GY-06-01)Xi'an Muinicipal Science and Technology Project,China(Grant No.201805037YD15CG21(28)).
文摘Plasma flow control is a new type of active flow control approach based on plasma pneumatic actuation.Dielectric barrier discharge(DBD) actuators have become a focus of international aerodynamic research.However,the practical applications of typical DBDs are largely restricted due to their limited discharge area and low relative-induced velocity.The further improvement of performance will be beneficial for engineering applications.In this paper,high-speed schlieren and high-speed particle image velocimetry(PIV) are employed to study the flow field induced by three kinds of plasma actuations in a static atmosphere,and the differences in induced flow field structure among typical DBD,extended DBD(EX-DBD),and tri-electrode sliding discharge(TED) are compared.The analyzing of the dynamic evolution of the maximum horizontal velocity over time,the velocity profile at a fixed horizontal position,and the momentum and body force in a control volume reveals that the induced velocity peak value and profile velocity height of EX-DBD are higher than those of the other two types of actuation,suggesting that EX-DBD actuation has the strongest temporal aerodynamic effect among the three types of actuations.The TED actuation not only can enlarge the plasma extension but also has the longest duration in the entire pulsed period and the greatest influence on the height and width of the airflow near the wall surface.Thus,the TED actuation has the ability to continuously influencing a larger three-dimensional space above the surface of the nlasma actuator.
