A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibrati...A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R ＆ D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers.展开更多
A method of calculating a possible stability loss by a rotating circular annular disc of variable thickness is suggested within the theory of perfect plasticity with the help of small parameter method. A characteristi...A method of calculating a possible stability loss by a rotating circular annular disc of variable thickness is suggested within the theory of perfect plasticity with the help of small parameter method. A characteristic equation for a critical radius of a plastic zone is obtained as a first approximation. The formula for the critical angular velocity, determining the stability loss of the disc according to the self-balanced form, is derived. The method using which we can take into account the disc’s geometry and loading parameters is also specified. The efficiency of the proposed method is shown in Section 5 while considering an illustrative example. The values of critical angular velocity of rotating are found numerically for different parameters of the disc.展开更多
Excitation functions of the dissipative products in the reaction 19F+51V have been measured from 102.25 to 109.50MeV by 250keV steps at θl = 21.7°, 36.1°and 40.5°. The rotation angular velocities ω an...Excitation functions of the dissipative products in the reaction 19F+51V have been measured from 102.25 to 109.50MeV by 250keV steps at θl = 21.7°, 36.1°and 40.5°. The rotation angular velocities ω and the energy coherence widths of the corresponding dinuclear systems were extracted. The coherence rotation and its importance in the reaction process have been discussed.展开更多
The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a ...The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.展开更多
Inspired by ballpoint pen,an optical biosensor is developed for detection of Salmonella using a mechanical step rotator with a dropper to greatly simplify operation,a high gradient magnetic field with immune magnetic ...Inspired by ballpoint pen,an optical biosensor is developed for detection of Salmonella using a mechanical step rotator with a dropper to greatly simplify operation,a high gradient magnetic field with immune magnetic nanobeads to specifically separate bacteria,and immune gold@platinum nanozymes with a smartphone to sensitively detect bacteria.First,the preloaded bacterial sample is drawn by the dropper to react with the immune magnetic nanobeads through repeated squeezing and releasing of the dropper,and the rotator is successively rotated and the dropper is repeatedly squeezed and released to achieve mixing of the bacteria,magnetic nanobeads and gold@platinum nanozymes,followed by magnetic separation to remove the background.Then,the conjugates are effectively washed with skim milk and ultrapure water,and the substrate are rapidly catalyzed into the product.Finally,the blue product is photographed and analyzed using a smartphone to obtain the Salmonella concentration.This biosensor could detect Salmonella as low as 56 CFU/mL in~25 min.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51079157)
文摘A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R ＆ D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers.
文摘A method of calculating a possible stability loss by a rotating circular annular disc of variable thickness is suggested within the theory of perfect plasticity with the help of small parameter method. A characteristic equation for a critical radius of a plastic zone is obtained as a first approximation. The formula for the critical angular velocity, determining the stability loss of the disc according to the self-balanced form, is derived. The method using which we can take into account the disc’s geometry and loading parameters is also specified. The efficiency of the proposed method is shown in Section 5 while considering an illustrative example. The values of critical angular velocity of rotating are found numerically for different parameters of the disc.
基金the National Natural Science Foundation of Chinathe Natural Science Foundation of Gansu Province,China.
文摘Excitation functions of the dissipative products in the reaction 19F+51V have been measured from 102.25 to 109.50MeV by 250keV steps at θl = 21.7°, 36.1°and 40.5°. The rotation angular velocities ω and the energy coherence widths of the corresponding dinuclear systems were extracted. The coherence rotation and its importance in the reaction process have been discussed.
基金Supported by the National Natural Science Foundation of China(6100201461101129+1 种基金6122700161072050)
文摘The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.
基金supported by Pinduoduo-China Agricultural University Research Fund(PC2023B02021).
文摘Inspired by ballpoint pen,an optical biosensor is developed for detection of Salmonella using a mechanical step rotator with a dropper to greatly simplify operation,a high gradient magnetic field with immune magnetic nanobeads to specifically separate bacteria,and immune gold@platinum nanozymes with a smartphone to sensitively detect bacteria.First,the preloaded bacterial sample is drawn by the dropper to react with the immune magnetic nanobeads through repeated squeezing and releasing of the dropper,and the rotator is successively rotated and the dropper is repeatedly squeezed and released to achieve mixing of the bacteria,magnetic nanobeads and gold@platinum nanozymes,followed by magnetic separation to remove the background.Then,the conjugates are effectively washed with skim milk and ultrapure water,and the substrate are rapidly catalyzed into the product.Finally,the blue product is photographed and analyzed using a smartphone to obtain the Salmonella concentration.This biosensor could detect Salmonella as low as 56 CFU/mL in~25 min.
