Particle Behavior and Aperture Optimization of Variable Vibration-Amplitude Screening Based on Discrete Element Method Simulation.

Recently, some novel screens were proposed based on the improved understanding of screening processes from particle-scale studies, one of which is the novel variable amplitude equal thickness vibration screen (VAETVS). This paper presents an investigation of using different aperture sizes to further optimize the VAETVS by the discrete element method (DEM). The screen was divided into three panels, and the aperture size of each panel was varied in the simulation. The particles' dynamics and spatial distribution were investigated to better understand the effects of varied amplitudes and aperture sizes on the screening efficiency. The results showed that the VAETVS can be effectively optimized by varied amplitude as well as varied aperture size for different screen panels. The amplitude variance is more effective for hard sieve particles and hindrance particles. It is also found that from the feed end to the discharge end, the difference in the distribution of particle mass between the coarse particles and the fine particles increases. Generally, such a difference can be increased with increasing aperture sizes. However, the effects of the apertures of the different panels were not the same. The simulated data were further analyzed by the Box-Behnken response surface method, which gave a mathematical model to predict the screening efficiency η with the varied apertures. From the model, the optimal aperture sizes are 7.5, 7.58, and 6.81 mm, yielding the maximum screening efficiency of 86.35%, and the optimal opening areas for the three panels are 35, 40, and 40%, respectively, yielding the maximum screening efficiency of 87.82%.

Research of the Collision Mechanics Model and Time-Frequency Characteristics during the Multistage Variable-Inclination Screening Process for Clean Coal.

Equal-thickness screening is a critical part of mineral processing; recently, the multistage variable-inclination equal-thickness screen (MSVIETS) has been utilized in the mining industry across the world. In this work, a model of the collision mechanics between particles and the multistage variable-inclination screen surface was established. The maximum collision force (F max) was found to be closely related to amplitude, frequency, screen surface inclination, and number of stages. The time-frequency response characteristics of multistage (3-, 4-, and 5-STAGE) screen surfaces were studied by the vibration test analysis system. The permeation screen distribution law of grain groups on the screen surface was revealed. The obtained results show the best screening performance can be obtained from the 5-STAGE scheme with a screening efficiency of higher than 95% and total mismatch content of less than 2%. The synergistic mechanism between two of the parameters was revealed by Box-Behnken response surface methodology (BBRSM). Then, the correlation between the screening evaluation index and the multiple parameters was obtained, and the significant order of the parameters influencing the screening evaluation index was F t > f > n.

The stripping effect of using high voltage electrical pulses breakage for waste printed circuit boards.

In this study, high voltage electrical pulses were utilized to process waste printed circuit boards to cost effectively liberate metal and nonmetal materials. Relative mass ωiand particles content ηiindexes were defined to assess the stripping effect produced by high voltage electrical pulses breakage. For relative mass level in the 0-10% range, in the -6+3 mm fraction, particles content accounted for 84.84% of the total particles, while the mechanical crushing only occupied 8.84%. Voltage and pulse experiments were carried out to investigate the crushing effect of high voltage electrical pulse breakage for printed circuit boards. It was found that when the voltage and pulse number was at 160 kV and 300, the stripping rate of copper was 98.56% and 92.58% in the -25+13 mm fraction respectively. The measured bending strength of the material revealed the selective crushing effect of high voltage electrical pulses in the different material interfaces. A liberation mechanism was elaborated by using the energy band theory, and a process model was utilized to reveal the mode of crushing. Furthermore, the microscopic appearance of the resulting product confirmed that copper underwent high-temperature melting, while the resin was decomposed during the crushing process. Compared to conventional mechanical crushing process, high voltage electrical pulses can better liberate metal-bearing than mechanical comminution technology.

Prognostic significance of FoxM1 expression in non-small cell lung cancer.

BACKGROUND: Various studies examined the relationship between FoxM1 overexpression with the clinical outcome in patients with non-small cell lung cancer (NSCLC), but yielded conflicting results. METHODS: Electronic databases updated to Jan 01, 2015 were searched to find relevant studies. A meta-analysis was conducted with eligible studies which quantitatively evaluated the relationship between FoxM1 overexpression and survival of patients with NSCLC Survival data were aggregated and quantitatively analyzed. RESULTS: We performed a meta-analysis of seven studies (n=860 patients) that evaluated the correlation between FoxM1 overexpression and survival in patients with NSCLC. Combined hazard ratios suggested that FoxM1 overexpression was associated with poor prognosis of overall survival (OS) (HR =1.73, 95% CI: 1.32-2.14) in patients with NSCLC. CONCLUSIONS: FoxM1 overexpression indicates a poor prognosis for patients with NSCLC.