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In the current study, the influence of TiO2 substituting SiO2 on the rheological and crystallization behavior of mold slags for casting Ti-containing steel was investigated through the measurement of the viscosity-temperature relationship, crystallization process and initial crystallization temperature. The structure of molten slags from the Raman spectrum and other parameters (NBO/T and Optical basicity) was compared to explain the difference of slag properties. With the substituting of SiO2 by TiO2 in slags from 5% to 20%, the viscosity of these slags at 1573 K decreased from 0.36 Pa s to 0.10 Pa s, and the viscous flow activation energy below the break temperature had the tendency to decrease. With the increase of the TiO2/SiO2 ratio from 0.25 to 4.00, the initial crystallization temperature of slags increased and the crystallization of slags were enhanced, which was related to the difference of the crystallization mode and the precipitation of dispersed crystals as nuclei. With the substituting of SiO2 by TiO2, the parameter NBO/T and optical basicity of molten slags increased, the complex network structure by the Raman spectra depolymerized gradually and the degree of polymerization decreased, which was related to the destruction of silicate/aluminate structure by the addition of TiO2 in slags. Hence, the substitution of SiO2 by TiO2 in slags simplified the network structure of mold slags, then lowered the viscosity and promoted the crystallization of slags.

Anti-backlash roller enveloping hourglass worm gear drives, as a new precision transmission system, has been extensively applied in robot joint design, and CNC (computer numerical control) machine tools. However, tooth profiles of the roller enveloping hourglass worms are spatial complex surfaces and very difficult to machine. The meshing and transmission properties such type of worm gear drive are especially sensitive to the errors in machining the tooth profiles of such worms. Thus, in order to improve the accuracy in machining their tooth profile surfaces and reduce the surface roughness, barriers to achieve precision machining of these complex surfaces have to be overcome. In the present study, an equation of grinding contact line for the roller enveloping hourglass worm gear drives with seven critical error parameters was for the first time established based on modern theory of gear meshing. Influence of each error parameter on the grinding contact line was decided through numerical analysis. Also, in order to find the best relationship between the grinding speed and the grinding feed rage, real contact patterns between the grinding rod and the machined worm tooth surface at different grinding speeds were observed using a metallurgical microscope and compared with the theoretical contact pattern calculated from the developed line of contact equation. Based on the obtained results, an innovative grinding method that can offset the loss of radius of the grinding rod was developed and a grinding process under the optimal rotational speed was presented. The proposed grinding process was then applied to generate the complex helical surface of a high precision roller enveloping hourglass worm. Outcomes of this study formed a profound theoretical and practical background for manufacturing and machining of the roller enveloping hourglass worm gear drives.

In gear transmission, temperature rise has a non-negligible impact on the accuracy, noise and transmission efficiency. However, there is no relevant research on the temperature rise of the anti-backlash single-roller enveloping hourglass worm (ASEHW) gear. To solve this problem, based on tribology principle and Hertz contact theory, the thermal power calculation method of the ASEHW gear was proposed for the first time and thermal analysis was carried out by Ansys software. The bulk temperature of the ASEHW gear under four different rotating speed (300 r/min, 600 r/min, 900 r/min, 1200 r/min) is calculated. The main factors causing temperature rise of the ASEHW gear are analyzed theoretically. Meanwhile, an experimental study is performed to verify the simulation results and validate the theory methods. The theory presented in this paper provides a solution for the thermal power calculation of ASEHW gear. This research provides a theoretical basis for further optimization of ASEHW gear.

The effect of MgO on the solidification and crystallization properties of ultrahigh-basicity mold flux was analyzed (i.e., comprehensive basicity R = 1.75). Results showed that with the increase of MgO content (0–6 wt%), the viscosity, melting temperature and break temperature decreases firstly, and then increases. The change of slag viscosity caused by the change of composition is indistinct, but the variation trend of melting temperature and break temperature is obvious. With the increase of MgO content, the crystallization temperature of ultrahigh-basicity slag decreases gradually, while the crystallization rate decreases firstly, and then increases. When the MgO content reaches 3%, the crystallization rate is the minimum. Research found that Ca4Si2F2O7 is the main precipitated phase in the slag, and as the MgO content continues to increase, the new phases of CaF2 and Ca3MgSi2O8 appear gradually.

Anti-backlash roller enveloping hourglass worm gears, as a new precision transmission system, has been extensively applied in robot joint design, packaging production line, and CNC (computer numerical control) machine tools. However, their corresponding transmission principles are seldom reported in the literature. Based on the theories of differential geometry and gear meshing, this paper carefully analyzes and compares meshing characteristics of anti-backlash single- and double-roller enveloping hourglass worm gears in terms of their transmission principle, engagement equation, induced normal curvature, lubrication angle, autorotation angle, entrainment velocity, helix angle, and distribution of contact curves. Major differences between these two roller enveloping hourglass worms are theoretically demonstrated through this study. Our results show that the anti-backlash single-roller enveloping hourglass worm (ASEHW) gears provide better performance with respect to gear meshing and transmission than the anti-backlash double-roller enveloping hour glass worm (ADEHW) gears. Also, compared with the ADEHW gears, the ASEHW gears are easier to fabricate, install, and calibrate. However, the ADEHW gears are more auto-adjustable in eliminating gear backlash. The outcomes of this study will form a theoretical background for futuristic design, application, and promotion of the anti-backlash roller enveloping hourglass worm gears.

This paper proposes a single-roller enveloping hourglass worm gear design and verifies its advantages compared to the existing double-roller worm gear system and the conventional worm gear set. Our hypothesis is that the single-roller worm gear with appropriate configurations and parametric values can eliminate the backlash in mating gear transmission while maintaining advantages of the double-roller worm gears. Also, the self-rotation of the rollers when they are in the worm tooth space (TS) will help the gear system to avoid jamming and gear tooth scuffing/seizing problems caused by zero backlash and thermal expansion. In order to test that hypothesis, a mathematical model for the single-roller enveloping hourglass worm gear is developed, which includes a gear engagement equation and a tooth profile equation. Using that model, a parametric study is conducted to inspect the influences of center distance, roller radius, transmission ratio, and the radius of base circle on the worm gear meshing characteristics. It is found that the most effective way in eliminating the backlash is to adjust the roller radius and the radius of base circle. Finally, a single-roller enveloping hourglass worm gear set is manufactured and scanned to generate a 3D computer model. That model is compared with a theoretical model calculated from the developed mathematical model. Comparison results show that both models match very well, which verifies the accuracy of the developed mathematical model and our initial hypothesis that it is possible to achieve transmissions with zero backlash by adjusting the design parameters.

This paper presents a novel high-performance standalone photovoltaic (PV) lighting system which can provide functional illumination based on high power White LEDs. An improved incremental conductance Maximum Power Point Tracking (MPPT) method is proposed in PV system to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A novel strategy to charge the battery is designed from the analyses and comparison results. In order to provide a steady-state operating environment for high power White LEDs, a specially designed LED drive module is implemented. Further more, a self-adapting dimming control is designed to maintain a stable indoor illuminance. Experimental results show the performance of the proposed photovoltaic lighting system.