A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathemat...A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.展开更多
A facile approach towards the synthesis of a novel hierarchical sieve-like structure of mesoporous silica nanoparticle aggregates(hsMSNA) is reported using a centrifugal method at room temperature, based on the Kelvin...A facile approach towards the synthesis of a novel hierarchical sieve-like structure of mesoporous silica nanoparticle aggregates(hsMSNA) is reported using a centrifugal method at room temperature, based on the Kelvin-Helmholtz instability and soft-template method. The developed approach is simple and can potentially be applied for scaled-up preparation. Importantly, scanning electron microscopy,transmission electron microscopy, small-angle X-ray diffraction, and nitrogen adsorption-desorption experiments characterize the mesoporous silica as hsMSNA consisting of 40-100 nm mesoporous silica nanoparticles piled at 1-2 μm cylindrical pores in sieve-like tissues. Further, various pore sizes and sievemesh-, and vesicular-like structures can be obtained by adjusting the reaction conditions. The BrunauerEmmett-Teller specific surface area is as large as 500 m~2/g with a 47 cm~3/g pore volume, facilitating easy drug loading and delivery. Cytotoxicity assays show that the samples are not cytotoxic under a high concentration of 200μg/mL. Finally, the high drug encapsulation efficiency and sustained release behaviors indicats the considerable potential of the hsMSNA as a drug delivery system in the field of nanomedicine.展开更多
The traditional Hassler-Brunner(HB)interpretation method of centrifuge capillary pressure is widely used in materials,soil,biotechnology,and especially in the petroleum industry.However,the assumptions of the traditio...The traditional Hassler-Brunner(HB)interpretation method of centrifuge capillary pressure is widely used in materials,soil,biotechnology,and especially in the petroleum industry.However,the assumptions of the traditional method cannot be simultaneously satisfied,the traditional method has been known to lead significant errors in some cases.In this paper,a new double integral method is proposed to evaluate the centrifuge capillary pressure of long tight sandstone samples.Both the changes of capillary length and interface of wetting phase and non-wetting phase fluids are considered by the new integral method,thus the average pressure and saturation derived from the proposed double integral method is more sufficient in theoretic foundation and clearer on physical meaning.By comparing with the measured capillary pressure of long tight sandstone core samples from porous plate,the capillary pressure calculated from traditional HB method is obviously smaller than the measured value,and the discrepancy increases with the decreasing core porosity.However,the average capillary pressure obtained by the proposed double integral method is remarkably consistent with the measured value.The findings of this study can help for better understanding of distribution of wetting phase fluid and average centrifuge capillary pressure in the core during centrifugal process.展开更多
Hot isostatic pressing(HIP)is a critical powder metallurgy technique for manufacturing high-performance components.However,achieving uniform powder distribution within complex capsules is challenging,particularly in c...Hot isostatic pressing(HIP)is a critical powder metallurgy technique for manufacturing high-performance components.However,achieving uniform powder distribution within complex capsules is challenging,particularly in critical low-density regions where inadequate powder filling leads to non-uniform deformation and potential part rejection after HIP.This study investigated the powder filling and packing densification behavior of Ti-6Al-4V particles through discrete element method(DEM)simulations to develop an enhanced densification technique targeting these critical regions.A new rotational centrifugal method was proposed to address this challenge.Results demonstrated that vertical vibration achieved limited improvement,and horizontal vibration exhibited non-uniform powder distribution.The proposed rotational centrifugal method at 200 rpm proved most effective,achieving the highest relative density with superior uniformity and rapid densification.The analysis in rotational motion revealed that rapid densification originates from consistent centrifugal forces.Upon stopping rotation,particles undergo localized vigorous motion,resulting in a slight decrease in relative density.To address this,an optimized deceleration scheme was developed.It achieved a relative density of 0.549,representing improvements of 70.5%over vertical vibration and 4.2%over horizontal vibration.These findings provide valuable insights for optimizing pre-HIP processing parameters for complex components,offering a promising solution for addressing powder filling challenges.展开更多
The high-concentration organic wastewater has great harm and high concentration of pollutants, which is a big problem in the wastewater treatment industry. The high-concentration organic wastewater in this paper takes...The high-concentration organic wastewater has great harm and high concentration of pollutants, which is a big problem in the wastewater treatment industry. The high-concentration organic wastewater in this paper takes landfill leachate as the experimental object, and takes corresponding measures to reduce the concentration of suspended solids as much as possible, so as to ensure the reliable operation of the subsequent treatment process. In the process of the experiment, it is necessary to simulate the process of mixing liquid in the reaction tank and blowing off the water, and remove the suspended substances in the reaction tank by centrifugal separation method. In this process, the influence of factors such as centrifugal time and rotational speed on the centrifugal effect is studied, and the corresponding centrifugal effect is determined when the conditions are different, and then the subsequent pretreatment and other processes are better carried out.展开更多
As a passive means of vibration reduction, particle damping is mainly applied to the horizontal or vertical steady field. However, it is seldom applied to centrifugal fields. Under high speed and heavy loading, the vi...As a passive means of vibration reduction, particle damping is mainly applied to the horizontal or vertical steady field. However, it is seldom applied to centrifugal fields. Under high speed and heavy loading, the vibration of tooth surfaces of gear transmissions becomes more severe shortening gear service life and augmenting noise. Under centrifugal loading, the particle system exhibits different characteristics, for example, particles are extruded at the end farthest from the center. We investigated gears with drilled via holes filled with damping particles. Using the discrete-element method, we developed an energy dissipation model for the particle system accounting for friction and inelastic collisions. Energy dissipation and damping characteristics of this system were analyzed. Experiments were also conducted with the gear system having different particle filling rates. The results show that this filling rate is an important parameter associated with particle damping in a centrifugal field. An unsuitable filling rate would significantly reduce damping effectiveness. With changes in rotation speed and load, the gear transmission system has different optimal filling rates. The results provide guidelines for the application of particle damping in centrifugal fields of gear transmissions.展开更多
文摘A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.
基金the National Key Basic Research Program of China(No.20131970096)the National Key R&D Plan(No.2016YFC0304502)
文摘A facile approach towards the synthesis of a novel hierarchical sieve-like structure of mesoporous silica nanoparticle aggregates(hsMSNA) is reported using a centrifugal method at room temperature, based on the Kelvin-Helmholtz instability and soft-template method. The developed approach is simple and can potentially be applied for scaled-up preparation. Importantly, scanning electron microscopy,transmission electron microscopy, small-angle X-ray diffraction, and nitrogen adsorption-desorption experiments characterize the mesoporous silica as hsMSNA consisting of 40-100 nm mesoporous silica nanoparticles piled at 1-2 μm cylindrical pores in sieve-like tissues. Further, various pore sizes and sievemesh-, and vesicular-like structures can be obtained by adjusting the reaction conditions. The BrunauerEmmett-Teller specific surface area is as large as 500 m~2/g with a 47 cm~3/g pore volume, facilitating easy drug loading and delivery. Cytotoxicity assays show that the samples are not cytotoxic under a high concentration of 200μg/mL. Finally, the high drug encapsulation efficiency and sustained release behaviors indicats the considerable potential of the hsMSNA as a drug delivery system in the field of nanomedicine.
基金supported by the Foundation of State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(No.PRP/open-1704)the Foundation of Education of Hu Bei Province,China(No.Q20171304)the Foundation of Key Laboratory of Exploration Technology for Oil and Gas Resources of Ministry of Education(No.K-2018-12)。
文摘The traditional Hassler-Brunner(HB)interpretation method of centrifuge capillary pressure is widely used in materials,soil,biotechnology,and especially in the petroleum industry.However,the assumptions of the traditional method cannot be simultaneously satisfied,the traditional method has been known to lead significant errors in some cases.In this paper,a new double integral method is proposed to evaluate the centrifuge capillary pressure of long tight sandstone samples.Both the changes of capillary length and interface of wetting phase and non-wetting phase fluids are considered by the new integral method,thus the average pressure and saturation derived from the proposed double integral method is more sufficient in theoretic foundation and clearer on physical meaning.By comparing with the measured capillary pressure of long tight sandstone core samples from porous plate,the capillary pressure calculated from traditional HB method is obviously smaller than the measured value,and the discrepancy increases with the decreasing core porosity.However,the average capillary pressure obtained by the proposed double integral method is remarkably consistent with the measured value.The findings of this study can help for better understanding of distribution of wetting phase fluid and average centrifuge capillary pressure in the core during centrifugal process.
基金supported by the National Defense Fundamental Research Foundation of China(grant No.JCKY2023204C033).
文摘Hot isostatic pressing(HIP)is a critical powder metallurgy technique for manufacturing high-performance components.However,achieving uniform powder distribution within complex capsules is challenging,particularly in critical low-density regions where inadequate powder filling leads to non-uniform deformation and potential part rejection after HIP.This study investigated the powder filling and packing densification behavior of Ti-6Al-4V particles through discrete element method(DEM)simulations to develop an enhanced densification technique targeting these critical regions.A new rotational centrifugal method was proposed to address this challenge.Results demonstrated that vertical vibration achieved limited improvement,and horizontal vibration exhibited non-uniform powder distribution.The proposed rotational centrifugal method at 200 rpm proved most effective,achieving the highest relative density with superior uniformity and rapid densification.The analysis in rotational motion revealed that rapid densification originates from consistent centrifugal forces.Upon stopping rotation,particles undergo localized vigorous motion,resulting in a slight decrease in relative density.To address this,an optimized deceleration scheme was developed.It achieved a relative density of 0.549,representing improvements of 70.5%over vertical vibration and 4.2%over horizontal vibration.These findings provide valuable insights for optimizing pre-HIP processing parameters for complex components,offering a promising solution for addressing powder filling challenges.
文摘The high-concentration organic wastewater has great harm and high concentration of pollutants, which is a big problem in the wastewater treatment industry. The high-concentration organic wastewater in this paper takes landfill leachate as the experimental object, and takes corresponding measures to reduce the concentration of suspended solids as much as possible, so as to ensure the reliable operation of the subsequent treatment process. In the process of the experiment, it is necessary to simulate the process of mixing liquid in the reaction tank and blowing off the water, and remove the suspended substances in the reaction tank by centrifugal separation method. In this process, the influence of factors such as centrifugal time and rotational speed on the centrifugal effect is studied, and the corresponding centrifugal effect is determined when the conditions are different, and then the subsequent pretreatment and other processes are better carried out.
文摘As a passive means of vibration reduction, particle damping is mainly applied to the horizontal or vertical steady field. However, it is seldom applied to centrifugal fields. Under high speed and heavy loading, the vibration of tooth surfaces of gear transmissions becomes more severe shortening gear service life and augmenting noise. Under centrifugal loading, the particle system exhibits different characteristics, for example, particles are extruded at the end farthest from the center. We investigated gears with drilled via holes filled with damping particles. Using the discrete-element method, we developed an energy dissipation model for the particle system accounting for friction and inelastic collisions. Energy dissipation and damping characteristics of this system were analyzed. Experiments were also conducted with the gear system having different particle filling rates. The results show that this filling rate is an important parameter associated with particle damping in a centrifugal field. An unsuitable filling rate would significantly reduce damping effectiveness. With changes in rotation speed and load, the gear transmission system has different optimal filling rates. The results provide guidelines for the application of particle damping in centrifugal fields of gear transmissions.
