Analysis of chaos behaviors of a bistable piezoelectric cantilever power generation system by the second-order Melnikov function

By applying the second order Melnikov function, the chaos behaviors of a bistable piezoelectric cantilever power generation system are analyzed. Firstly, the conditions for emerging chaos of the system are derived by the second order Melnikov function. Secondly, the effects of each item in chaos threshold expression are analyzed. The excitation frequency and resistance values, which have the most influence on chaos threshold value, are found. The result from the second order Melnikov function is more accurate compared with that from the first order Melnikov function. Finally, the attraction basins of large amplitude motions under different exciting frequency, exciting amplitude, and resistance parameters are given.

Research and Practice of Traffic Lights and Traffic Signs Recognition System Based on Multicore of FPGA

This thesis will present the research and practice of traffic lights and traffic signs recognition system based on multicore of FPGA. This system consists of four parts as following: the collection of dynamic images, the preprocessing of gray value, the detection of the edges and the patterning and the judgment of the pattern matching. The multiple cores system is consist of three cores. Each core parallels processes the incoming images from camera collection in terms of different colors and graphic elements. The image data read in from the camera works as the sharing data of the three cores.

Highly efficient generation of blastocyst-like structures from spliceosomes-repressed mouse totipotent blastomere-like cells

Mammalian embryogenesis begins with a totipotent zygote.Blastocyst-like structures can be captured by aggregated cells with extended pluripotent properties in a three-dimensional(3D)culture system.However,the efficiency of generating blastoids is low,and it remains unclear whether other reported totipotent-like stem cells retain a similar capacity.In this study,we demonstrated that spliceosomal repression-induced totipotent blastomere-like cells(TBLCs)form blastocyst-like structures within around 80%of all microwells.In addition,we generated blastoids initiating from a single TBLC.TBLC-blastoids express specific markers of constituent cell lineages of a blastocyst and resemble blastocyst in cell-lineage allocation.Moreover,singlecell RNA sequencing revealed that TBLC-blastoids share a similar transcriptional profile to natural embryos,albeit composed of fewer primitive endoderm-like cells.Furthermore,TBLC-blastoids can develop beyond the implantation stage in vitro and induce decidualization in vivo.In summary,our findings provided an alternative cell type to efficiently generate blastoids for the study of early mouse embryogenesis.

Experimental investigation on unstart-restart hysteresis of a supersonic inlet during throat regulation

The hysteresis during the throat regulation process of a supersonic variable inlet is unconducive to restart.Hence,detailed experimental studies of such a hysteresis and its control are necessary.A throat variable supersonic inlet was designed at a shock-on-lip Mach number of 4.0 and an Internal Contraction Ratio(ICR)ranging over 1.21–2.94.Meanwhile,a distributed bleed system was proposed to suppress the hysteresis.The wind tunnel tests were conducted at Mach number 2.9.The throat regulation processes were recorded using a high-speed schlieren and dynamic pressure acquisition system.The results indicate that the unstart and restart ICRs during the uncontrolled inlet’s throat regulation process were 1.95 and 1.48,respectively,demonstrating an unstart-restart hysteresis.Four typical flowfields were summarized during the uncontrolled inlet’s restart process.The proposed bleed control increased the unstart and restart ICRs to 2.06 and 1.75,respectively,and the inlet realized the designed state as the ICR was further decreased to 1.67.The controlled inlet’s hysteresis loop was decreased compared to the uncontrolled inlet.Finally,the mechanism of the hysteresis,dominated by the entrance separation-induced wave system,was clarified.The mechanisms of the bleed control to broaden the unstart and restart boundaries and suppress the hysteresis were elucidated.

Flow response hysteresis of throat regulation process of a two-dimensional mixed-compression supersonic inlet

The variable geometry supersonic inlet tends to decrease the throat area to reduce the Mach number upstream of the terminal shock,so as to reduce the flow loss.However,excessive Internal Contraction Ratio(ICR)exposes the inlet to a greater risk of unstart,which inevitably results in a process of increasing the throat area to aid the inlet restart.In the above throat regulation process,the inlet undergoes the start,unstart,and restart states in turn.In order to reveal the flow structure and mechanism of this process,a two-dimensional unsteady numerical simulation combined with a dynamic mesh technique were employed.The shock-on-lip Mach number of the studied inlet is 4.0 and the flight angle of attack is+6°.Analysis was focused on the state with a freestream Mach number of 3.0.The results clearly show that the flow response hysteresis appears,and restart is only realized when the throat area is obviously increased as compared to that of unstart due to the historical unstart flow structure.In addition,three typical flow fields were analyzed,and it is found that the separation ahead of the inlet was the key factor affecting the hysteresis.Finally,unstart and restart boundaries of the inlet were discussed,and the factors influencing its deviation from the typical boundaries of dual-solution area were analyzed.The newly predicted unstart and restart boundaries are much closer to the CFD results.

A pillar[5]arene-based side-chain pseudorotaxanes and polypseudorotaxanes as novel fluorescent sensors for the selective detection of halogen ions

A pseudorotaxane and its polypseudorotaxanes formed between pillar[5]arene moieties and noctylpyrazinium cations as novel fluorescent sensors for the selective detection of halogen ions were reported.A collapse of these pillar[5]arene-based pseudorotaxanes and polypseudorotaxanes occurred upon the addition of Cl,Br,and I（tetrabutylammonium salts）,respectively,leading to their fluorescence recovery.The fluorescence enhancement of the pseudorotaxane and the polypseudorotaxanes increases in the order of I

Flowfield of a helicopter submerged inlet with power output shaft

The submerged inlet is an attractive configuration for advanced helicopters due to its high stealth performance and low external drag.In this paper,a submerged inlet,integrated with a ROBIN helicopter fuselage and a simplified power output shaft,is experimentally and numerically investigated to obtain the basic flow characteristics under a freestream velocity of 23.6 m/s.The results indicate that the pylon ahead of the inlet induces a horseshoe vortex.Though the vortex is ingested into the inlet,it has little effect on the internal flows and can be neglected.When the airflow enters into the inlet,it interacts with the shaft with a large incidence angle,yielding a vortex pair.At the leeside of the shaft,the two side flows of the shaft impinge at the center plane,generating a local high-pressure region at the azimuthal angle of 180°,which forces the boundary layer to roll up a counter-rotating vortex pair.In addition,the airflow adjacent to the cowl lip accelerates rapidly,resulting in a local low-pressure region at the azimuthal angle of 0°.Therefore,the inlet duct has a strong circumferential pressure gradient,which originates from an azimuthal angle of 180°to 0°and induces a vortex pair at the azimuthal angle of 0°.The three vortex pairs are the main origins of the distortion at the duct exit plane,among which the one near the cowl lip with the azimuthal angle of 0°plays the dominant role.Additionally,as the velocity ratio increases from 3.9 to 5.5,the circumferential pressure gradient and the cowl lip vortex get intensified,which causes that the total-pressure recovery coefficient drops by 0.5%and the distortion index increases by 28%.

Selective detection of phosphaphenanthrene-containing luminophors with aggregation-induced emission enhancement to transition metal ions

Transition metal ions(Pb^(2+),Zn^(2+),Cd^(2+),Co^(2+),Mn^(2+),Cu^(2+),Ni^(2+),Hg^(2+),Ag^(+),Fe^(3+))in water are used to quench emission of 2-(6-oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)-1,4-phenylene-bis(p-pentyloxylbenzoate)s(MD5)with aggregation-induced emission enhancement(AIEE)in water-acetonitrile(AN)mixture(80:20 by volume).Among all metal ions,Fe^(3+)exhibits the highest quenching efficiency on AIEE of MD5 even when the concentration of Fe^(3+)is lower than 1×10^(-6) mol/L.The quenching efficiency of Hg^(2+)is lower than that of Fe^(3+)at the same concentration,though MD5 is used to detect Hg^(2+)efficiently,too.To other metal ions,low quenching efficiency has few relations with a wider concentration range.The UV absorbance spectra show only red shift of absorbance wavelength in the presence of Hg^(2+)and Fe^(3+),which indicates a salt-induced Jaggregation.SEM photos reveal larger aggregation and morphological change of nanoparticles of MD5 in water containing Hg^(2+)and Fe^(3+),which reduce the surface area of MD5 emission for further aggregation.The selective quenching effect of transition metal ions to emission of MD5 has a potential application in chemical sensors of some metal ions.