Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown...Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown through the plug during stirring create a strong thermal shock impact on the materials.This can affect its service life and restrict the safety and efficiency of steel making if the plug fails during use.In this work,the influence of the particle size distribution (PSD) and amount of reactive alumina on the sintering behavior of ultra-low cement bonded corundum-spinel based castables was investigated on lab scale.The relationship between sintering reactivity of matrix and thermal shock resistance of castables was evaluated in detail.Results show that the sintering of castables can be intensified by using finer reactive alumina.However,excessive sintering of the castable through finer reactive alumina is negative for thermal shock resistance.The microstructure characterization reveals that castables with more intense sintering show denser matrix structure,which is less effective in hampering crack propagation and therefore results in decline of their thermal shock resistance.展开更多
An improved on-chip CMOS astable multivibrator is proposed, which overcomes the shortcomings of the traditional one that the signal duty-cycle is depending on model parameters, and generates stable clock signal with d...An improved on-chip CMOS astable multivibrator is proposed, which overcomes the shortcomings of the traditional one that the signal duty-cycle is depending on model parameters, and generates stable clock signal with duty-cycle equaling 50%. The latch-up effect has been prevented on the improved circuit. It is extremely important that all the excellent performances of the improved astable multivibrator have been achieved with a dynamic power consumption equaling its predecessor one. The advantage of the structure has been verified by SPICE simulation.展开更多
For the proper use of micropowders in castables,slurries and fired samples were prepared with two kinds of corundumspinel micropowders(D and G).The effects of the solid content and disperser WSM-R1 on the rheological ...For the proper use of micropowders in castables,slurries and fired samples were prepared with two kinds of corundumspinel micropowders(D and G).The effects of the solid content and disperser WSM-R1 on the rheological properties of the slurries were studied.The sintering properties and the slag corrosion resistance of the fired samples were also researched.The results show that:the slurries all show pseudoplastic rheological characteristics.With the same solid content,the slurry with micropowder G has higher initial viscosity than that with micropowder D.Disperser WSM-R1 significantly reduces the initial viscosity of the two slurries and plays a more obvious dispersing effect on the slurry with micropowder G.The fired sample with micropowder G has higher bulk density,lower apparent porosity and better corrosion resistance than that with micropowder D.展开更多
Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in...Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in metallurgical industry has been reviewed,focusing on the results reported in the past decade.The research and reutilization methods of used refractories were discussed.For the research of used refractories,the results of two aspects,the performance and surface corrosion characteristics,are summarized.Then,the advances in research on recycling technology of several main kinds of used refractories,such as MgO-C,Al2O3-SiC-C,Al2O3-MgO-C,magnesium-chrome,and corundum-spinel refractories were summarized and discussed in detail.Some results of the author’s group were reported等线accompanied by these comments.The microstructure and chemical composition were studied by scanning electron microscopy and energy dispersion spectra,and the properties of the refractories were analyzed.Afterwards,the scope of application of materials was determined according to the classification and analysis of refractories.Finally,the large-scale application of used refractories and an outlook is given to future developments of the entire recycling industry.展开更多
The design and development of a timer based revolution per minute(RPM)measurement system were described in this paper.The rotating shaft of a dc motor was used to measure the RPM and timer integrated circuit(IC)555 wa...The design and development of a timer based revolution per minute(RPM)measurement system were described in this paper.The rotating shaft of a dc motor was used to measure the RPM and timer integrated circuit(IC)555 was used in astable mode.The frequency of timer output waveform measured by a digital storage oscilloscope(DSO)is almost linearly proportional to the RPM of rotating shaft,and the RPM also linearly varies with the change of the external input voltage level.Hence the linear relationship between the frequency of timer output waveform and the RPM can be obtained.The main advantages of this developed system are linear input-output relationship,small size,easy to carry and cost effective.展开更多
基金the National Natural Science Foundation of China(51572244 and U1604252)for supporting this work
文摘Purging plugs installed in the bottom of steel ladles are widely used for the secondary refining of high quality steel grades.The dynamic service conditions and temperature gradients caused by the cold inert gas blown through the plug during stirring create a strong thermal shock impact on the materials.This can affect its service life and restrict the safety and efficiency of steel making if the plug fails during use.In this work,the influence of the particle size distribution (PSD) and amount of reactive alumina on the sintering behavior of ultra-low cement bonded corundum-spinel based castables was investigated on lab scale.The relationship between sintering reactivity of matrix and thermal shock resistance of castables was evaluated in detail.Results show that the sintering of castables can be intensified by using finer reactive alumina.However,excessive sintering of the castable through finer reactive alumina is negative for thermal shock resistance.The microstructure characterization reveals that castables with more intense sintering show denser matrix structure,which is less effective in hampering crack propagation and therefore results in decline of their thermal shock resistance.
文摘An improved on-chip CMOS astable multivibrator is proposed, which overcomes the shortcomings of the traditional one that the signal duty-cycle is depending on model parameters, and generates stable clock signal with duty-cycle equaling 50%. The latch-up effect has been prevented on the improved circuit. It is extremely important that all the excellent performances of the improved astable multivibrator have been achieved with a dynamic power consumption equaling its predecessor one. The advantage of the structure has been verified by SPICE simulation.
基金fully funded by National Natural Science Foundation of China and Youth Fund Projects(51802235)
文摘For the proper use of micropowders in castables,slurries and fired samples were prepared with two kinds of corundumspinel micropowders(D and G).The effects of the solid content and disperser WSM-R1 on the rheological properties of the slurries were studied.The sintering properties and the slag corrosion resistance of the fired samples were also researched.The results show that:the slurries all show pseudoplastic rheological characteristics.With the same solid content,the slurry with micropowder G has higher initial viscosity than that with micropowder D.Disperser WSM-R1 significantly reduces the initial viscosity of the two slurries and plays a more obvious dispersing effect on the slurry with micropowder G.The fired sample with micropowder G has higher bulk density,lower apparent porosity and better corrosion resistance than that with micropowder D.
基金National Key R&D Program of China(Grant No.2018YFC1901504)National Natural Science Foundation of China(Grant No.51872268).
文摘Due to thermal stability and excellent resistance to slag erosion,the used refractories can be recycled as the main raw material for some refractories.In this article the latest developments about used refractories in metallurgical industry has been reviewed,focusing on the results reported in the past decade.The research and reutilization methods of used refractories were discussed.For the research of used refractories,the results of two aspects,the performance and surface corrosion characteristics,are summarized.Then,the advances in research on recycling technology of several main kinds of used refractories,such as MgO-C,Al2O3-SiC-C,Al2O3-MgO-C,magnesium-chrome,and corundum-spinel refractories were summarized and discussed in detail.Some results of the author’s group were reported等线accompanied by these comments.The microstructure and chemical composition were studied by scanning electron microscopy and energy dispersion spectra,and the properties of the refractories were analyzed.Afterwards,the scope of application of materials was determined according to the classification and analysis of refractories.Finally,the large-scale application of used refractories and an outlook is given to future developments of the entire recycling industry.
文摘The design and development of a timer based revolution per minute(RPM)measurement system were described in this paper.The rotating shaft of a dc motor was used to measure the RPM and timer integrated circuit(IC)555 was used in astable mode.The frequency of timer output waveform measured by a digital storage oscilloscope(DSO)is almost linearly proportional to the RPM of rotating shaft,and the RPM also linearly varies with the change of the external input voltage level.Hence the linear relationship between the frequency of timer output waveform and the RPM can be obtained.The main advantages of this developed system are linear input-output relationship,small size,easy to carry and cost effective.
