In this paper, two-dimensional numerical simulations of the head-on and off-center binary collision of liquid drops are carried out using lattice Boltzmann method. The coalescence process of drops colliding is freely captured, regardless of tracking equations and drops model. Special attention is paid to investigate the effect of the Weber number, impact velocity, drop size ratio on the coalescence process. The research results demonstrate that numerical results of lattice Boltzmann method are in agreement with qualitatively experimental data in the same Weber number. It is also noted that the first oscillation period is invariably shorter than the second period, regardless of the Weber number. It is further found that variation of the first period of oscillation in off-center collision of two equal-size drops as function of Weber number are higher than the variation of the first period of oscillation in head-on collision of two equal-size drops in the same Weber number.

Random Carrier-Frequency (RCF) modulation has been applied to DC/DC converters, reducing conducted EMI significantly. The selection of the duty cycle is critical in terms of suppressing EMI level in RCF modulation. But limited related literature is available. In this paper, we analysis the effect of duty cycle on suppressing EMI level by deduced the expression of the amplitude of switching voltage power spectra under the RCF mode and describe the change trend of PSD versus f in the case of different duty cycle, providing the theoretical basis of selection of duty cycle for low EMI level.

Aim To explore the application value of modified closed biopsy technique in puncture biopsy of rabbit VX2 transplanted bone tumor model.Methods VX2 tumor was transplanted into the bilateral tibia of 30 rabbits through the tibial plateau to make the model of VX2 transplanted bone tumor. Seven days after modeling, the proximal tibia biopsy was performed under the guidance of X-ray, and the biopsy specimen was examined pathologically. The left leg was biopsied with modified closed biopsy technique (experimental group) and the right leg was biopsied with hollow needle (control group). After 14 days of modeling, all rabbits were killed after X-ray examination around the puncture hole, and the soft tissue around the puncture hole was taken for pathological examination, and the expression levels of PCNA and CD34 in the tissue extract were detected by enzyme-linked immunosorbent assay (ELISA).Results By the end of the experiment, a total of 3 rabbits died, and finally 27 rabbits were included in the study. Tumor cells were detected in all the intramedullary specimens obtained by puncture biopsy. On the 14th day after modeling, X-ray showed that the occurrence rate of periosteal reaction and extraosseous high density shadow around the puncture hole was 14.81% (4/27) in the experimental group and 40.74% (11/27) in the control group. the difference was statistically significant (P<0.05). The pathological results of soft tissue around the puncture hole showed that the tumor cell metastasis rate was 29.63% (8/27) in the experimental group and 100% (27/27) in the control group, and the difference was statistically significant (P<0.05).The expression levels of PCNA and CD34 in the experimental group were lower than those in the control group (P < 0.05). Conclusion Both the modified closed biopsy technique and needle aspiration biopsy can provide sufficient biopsy tissue for the diagnosis of VX2 transplanted bone tumor in rabbits. At the same time, the improved closed biopsy technique has a certain application value in preventing local metastasis of tumor cells along the puncture channel.