Effect of droplet characteristics on liquid-phase distribution in spray zone of internal mixing air-mist nozzle

In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab quality.In order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect,the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT software.Results show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center,thus,the liquid volume fraction in the center is higher than that of either side.As the droplet diameter increases,the region of high liquid volume fraction on the slab surface becomes wider,and the liquid phase distribution in the slab width direction becomes uneven.Although increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone,the distribution becomes more uneven due to more liquid reaches the slab surface per unit time.A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data.A nozzle spacing of 210 mm was recommended under the working conditions in this study,which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.

Cytoplasmic translocation of Cx32 mediates cisplatin resistance in ovarian cancer cells

OBJECTIVE To investigate the underlying mechanism of drug resistance to cisplatin and increasing the sensitivity to therapeutic drugs are key steps towards the improved treatment of patients with ovarian cancer.Gap junction(GJ)and connexin(Cx)are closely related to tumor formation,but the relationship between cisplatin resistance and GJ or Cx are undetermined.METHODS We established the cisplatin-resistant human ovarian cancer cell line A2780-CDDP over an 11-month period,with the concentration of cisplatin gradually increasing from 0.5 g·L^(-1) to 16 g·L^(-1).To explore the effect of GJ in the process of cisplatin resistance,we investigated GJ using a parachute dyecoupling assay in A2780-RI(1.2),A2780-RI(1.7),A2780-RI(2.9),A2780-RI(4.3)and A2780-CDDP cells.We further explored whether the Cxs responsible for GJ were related to cisplatin resistance.In A2780-RI(1.2),A2780-RI(1.7),A2780-RI(2.9),A2780-RI(4.3)and A2780-CDDP,we used q-PCR to analyze the levels of Cx43,Cx40,Cx37,and Cx32.To confirm the effect of Cx32 on cisplatin resistance,we knocked down Cx32 in A2780-CDDP cells with si RNA-Cx32.As GJ was decreased whereas Cx32 expression was elevated during the cisplatin resistance process,it drove us to explore the underlying mechanism.To resolve this issue,we extracted membrane-bound and cytoplasmic proteins from A2780 and A2780-CDDP cells.RESULTS Here we showed that cisplatin resistance was correlated to the loss of GJ and the upregulation of Cx32 expression.Enhancing GJ in A2780-CDDP cells could increase the apoptotic response to cisplatin treatment.Furthermore,although Cx32 expression was increased in A2780-CDDP cells,it was more localized to the cytoplasm rather than in the membrane,and knockdown of Cx32 in A2780-CDDP cells sensitized them to cisplatin treatment.CONCLUSION In summary,Cx32 is involved in cisplatin resistance,and cytoplasmic Cx32 plays an important role in chemoresistance.

Acute Respiratory Disease at a Chinese Military Recruitment Training Center: Three-Year Consecutive Investigation

Background Military recruits are at a higher risk of acute respiratory disease(ARD) and the causative agents might change over time, which needs to be investigated. Methods The nasopharyngeal swabs and blood samples were consecutively collected from conscripts for three years in a military training center. The real-time fluorescent quantitative PCR assays were conducted for 15 species of common respiratory pathogens; the serum anti-Legionella pneumophila antibodies were detected by indirect immunofluorescence(IIF) assay, and serum anti-Microplasma pneumoniae antibodies, serum anti-influenza B virus and anti-influenza A virus-Ig M and Ig G were detected by ELISA. Results The prevalences of ARD were 59.3%(108/182) in 2008, 23.3%(50/215) in 2009,and 19.6%(40/204) in 2010. Among the patients with ARD from 2008 to 2010, the influenza B virus infection accounted for 45.4%, 30.0% and 55.0%, and seasonal influenza A virus infection for 8.3%, 8.0% and 5.0%, respectively; the positive rates of serum anti-Legionella pneumophila and anti-Microplasma pneumoniae antibodies in recruits was lower than 10% each year respectively in the three years without diagnostic significance. Conclusion The early appropriate diagnosis and treatment of ARD in military personnel will ensure the power strength of armed forces.

Effects of argon blowing at tundish upper nozzle on multiphase flow behavior in nozzle

In continuous casting,the argon blowing at the tundish upper nozzle is usually used to prevent nozzle clogging,whose effect is closely related to the migration of argon bubbles and the flow behavior of the liquid steel in the nozzle.Here,to investigate the effects of argon blowing at the tundish upper nozzle on multiphase flow behavior in nozzle,a threedimensional model of the tundish–nozzle–mold was established for numerical simulation.The results indicate that the argon bubbles injected from the inner wall of the tundish upper nozzle first move downward along the nozzle wall under the action of the liquid steel.As the distance from the tundish upper nozzle increases,the argon bubbles gradually diffuse to the center of the nozzle.Compared with no argon blowing,the liquid steel velocity increases in the center of the nozzle and decreases near the wall with argon blowing.With increasing the argon flow rate,the concentration of bubbles in the nozzle increases,and the process of bubble group diffusion to the center region of the nozzle speeds up.This in turn increases the liquid steel velocity at the center of the nozzle but reduces near the wall.With increasing the casting speed,the concentration of bubbles in the nozzle decreases,the length of the bubble group near the nozzle wall is extended,and the liquid steel velocity at the center region and near-wall region of the nozzle increases.The mechanism of argon blowing at the tundish upper nozzle to prevent nozzle clogging is mainly realized by the isolation effect of the argon bubble group on the inner wall of the nozzle.

Set Function Optimization

This article is an introduction to recent development of optimization theory on set functions,the nonsubmodular optimization,which contains two interesting results,DS(difference of submodular)functions decomposition and sandwich theorem,together with iterated sandwich method and data-dependent approximation.Some potential research problems will be mentioned.