Jet agitation is known as a maintenance-free stirring technique for nuclear wastewater treatment and demonstrates great potential in transport of radioactive particles.Removal processes of horizontal sediment beds dri...Jet agitation is known as a maintenance-free stirring technique for nuclear wastewater treatment and demonstrates great potential in transport of radioactive particles.Removal processes of horizontal sediment beds driven by impinging jets were experimentally investigated using image capture and processing technique.The beds were composed of heavy fine particles with particle density ranging from 3700 to 12600 kg·m^(-3) and particle diameter from 5 to 100 μm.The jet Reynolds number varied between 4300 and 9600.The single-phase large eddy simulation method was used for calculating both jet flow characteristics and wall shear stresses.The effects of jet strength,particle density,particle diameter,and bed thickness on bed mobility in terms of the critical Shields numbers were considered.Specifically,the critical Shields number was found to be intricately related to properties of particles,and independent of jet intensity.A new Shields number curve for stainless-steel particles was found,and a model was proposed to predict the transport rate of thin beds,with R^(2)=0.96.展开更多
This paper presents the results of a numerical investigation of micro-sized particle removal by droplet impact. Computational fluid dynamics simulation is used to calculate the flow distribution of droplet impact on a...This paper presents the results of a numerical investigation of micro-sized particle removal by droplet impact. Computational fluid dynamics simulation is used to calculate the flow distribution of droplet impact on a flat surface. The hydrodynamic forces exerted on the particle are then computed. Key factors controlling particle removal are discussed. Both hydrophilic and hydrophobic surfaces are considered. The flow distributions,especially the front edge expanding upon impact at microscale,strongly depend on surface wettability. The associated hydrodynamic forces on the particles vary accordingly. In addition, the impact on a dry surface can produce higher removal efficiency than that on a wet surface. Under the same impact conditions, the drag force exerted on a particle residing on a dry surface can be three orders of magnitudes larger than on a wet surface. Improving droplet impact velocity is more effective than improving droplet size.展开更多
The particle characterization from the influent and effluent of a chemical-biological flocculation （CBF） process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatme...The particle characterization from the influent and effluent of a chemical-biological flocculation （CBF） process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatment （CEPT） process and a primary sediment tank process were also analyzed for comparison. The results showed that CBF process was not only effective for both the big size particles and small size particles removal, but also the best particle removal process in the three processes. The results also indicated that CBF process was superior to CEPT process in the heavy metals removal. The high and non-selective removal for heavy metals might be closely related to its strong ability to eliminate small particles. Samples from different locations in CBF reactors showed that small particles were easier to aggregate into big ones and those disrupted flocs could properly flocculate again along CBF reactor because of the biological flocculation.展开更多
The ICRF (Ion Cyclotron Range Frequency) cleaning technique has been used as a routine wall cleaning method in the HT-7 superconducting tokamak. In a wide range of toroidal field, the removal rate of residual gas by I...The ICRF (Ion Cyclotron Range Frequency) cleaning technique has been used as a routine wall cleaning method in the HT-7 superconducting tokamak. In a wide range of toroidal field, the removal rate of residual gas by ICRF cleaning was about twenty times higher than that of glow discharge cleaning (GDC). At different gas pressure and RF power levels, the ICRF cleaning is studied carefully. A good impurity cleaning effect and a very high hydrogen removal rate were obtained. The removal rate of hydrogen by 5 kW ICRF cleaning achieved was 1.6 × 10-5 Tirr.1/s.And the relationships among pressure P, outgassing rate Q, atomic layers L absorbed on surface and the cleaning mode were discussed briefly.展开更多
Negative air ions(NAIs)in indoor environments have been suggested to positively impact human health by effectively reducing particulate contamination and gaseous pollutants,as well as inhibiting the growth of microorg...Negative air ions(NAIs)in indoor environments have been suggested to positively impact human health by effectively reducing particulate contamination and gaseous pollutants,as well as inhibiting the growth of microorganisms,bacteria and viruses.This study investigates the common ionizers with different module types,and the mechanism of NAIs for enhancing indoor air quality,as well as the positive and negative impacts on human health.The association between NAI concentrations and human health outcomes is examined,and alternative measures to balance beneficial and unavailing effects are investigated.While NAIs demonstrate efficacy in removing particulate pollutants,alleviating depression,enhancing cognitive function and even stimulating sympathetic activity,it is pertinent to acknowledge the presence of contradictory findings concerning their effects on cardiac autonomic function and respiratory physiology.To address this complexity,it is imperative to consider alternative measures that strike a balance between the beneficial and unavailing effects of NAIs.These measures can encompass a general assessment of the characteristics of particulate pollutants,a strategic selection of ionizer technologies,and adherence to the recommended optimal concentration thresholds of NAIs.展开更多
A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, t...A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, the discrete phase model （DPM） was applied to generate particle trajectories, and the governing equations are solved using the finite volume method. To validate this model, the numerical results were compared with data obtained from a full-scale physical model. The results show that： （1） the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks, giving an average relative error of velocities between simulated and measured values of 18% from contour maps of velocity magnitudes; （2） the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank. The average relative error of the removal rates between simulated and measured values was 11%. The DPM can be used to assess the self-cleaning capability of an octagonal tank; （3） a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations. The velocity distribution was uniform with an average velocity of 15 cm/s; the velocity reached 0.8 m/s near the inlet pipe, which can result in energy losses and cause wall abrasion; the velocity in tank corners was more than 15 cm/s, which suggests good water mixing, and there was no particle sedimentation. The percentage of particle removal for octagonal tanks was 90% with the exception of a little accumulation of 〈5 mm particle in the area between the inlet pipe and the wall. This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.展开更多
The effect of a non-ionic surfactant on particles removal in post-CMP cleaning was investigated. By changing the concentration of the non-ionic surfactant, a series of experiments were performed on the 12 inch Cu patt...The effect of a non-ionic surfactant on particles removal in post-CMP cleaning was investigated. By changing the concentration of the non-ionic surfactant, a series of experiments were performed on the 12 inch Cu pattern wafers in order to determine the best cleaning results. Then the effect of the surfactant on the reduction of defects and the removal of particles was discussed in this paper. What is more, the negative effect of a non-ionic surfactant was also discussed. Based on the experiment results, it is concluded that the non-ionic surfactant could cause good and ill effects at different concentrations in the post-CMP cleaning process. This understanding will serve as a guide to how much surfactant should be added in order to achieve excellent cleaning performance.展开更多
Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velo...Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velocimetry(PTV)technique was employed to characterize the particle removal displacement and velocity in the interface between a transparent copper film and a porous polyvinyl alcohol(PVA)brush during the cleaning process.Several different cleaning conditions including rotation speeds,loading pressure and cleaning agent were examined and the particle removal rate was compared.Elastic and friction removal,hydrodynamic removal and mixed-type removal are the three types of particle removal.Particles with an arc trace and uniform velocity curves were removed by friction and elastic force which were related to the brush load.Particles with a random trace and fluctuant velocity curves were removed by hydrodynamic force which was determined by the brush rotation speed.The increase of particle removal rate(PRR)with brush rotation speed is a logistic function.It is easier to improve PRR by increasing the brush load or by adding surfactant than by increasing the brush rotation speed.展开更多
In the paper,the behavior of the particle acted by the oscillating bubble is studied using a high-speed video camera.The bubble is generated using a very low voltage of 55 V.Images are captured at a speed of 15000 fps...In the paper,the behavior of the particle acted by the oscillating bubble is studied using a high-speed video camera.The bubble is generated using a very low voltage of 55 V.Images are captured at a speed of 15000 fps(frames per second).It is found that the velocity of the particle is dependent on the liquid viscosity,particle size,and tube diameter.Particle velocity decreases with the increase of the glycron-water mixture viscosity.A model is presented to predict the velocity and verified by experimental results.These observations may be beneficial for the application in medical treatment.展开更多
文摘Jet agitation is known as a maintenance-free stirring technique for nuclear wastewater treatment and demonstrates great potential in transport of radioactive particles.Removal processes of horizontal sediment beds driven by impinging jets were experimentally investigated using image capture and processing technique.The beds were composed of heavy fine particles with particle density ranging from 3700 to 12600 kg·m^(-3) and particle diameter from 5 to 100 μm.The jet Reynolds number varied between 4300 and 9600.The single-phase large eddy simulation method was used for calculating both jet flow characteristics and wall shear stresses.The effects of jet strength,particle density,particle diameter,and bed thickness on bed mobility in terms of the critical Shields numbers were considered.Specifically,the critical Shields number was found to be intricately related to properties of particles,and independent of jet intensity.A new Shields number curve for stainless-steel particles was found,and a model was proposed to predict the transport rate of thin beds,with R^(2)=0.96.
文摘This paper presents the results of a numerical investigation of micro-sized particle removal by droplet impact. Computational fluid dynamics simulation is used to calculate the flow distribution of droplet impact on a flat surface. The hydrodynamic forces exerted on the particle are then computed. Key factors controlling particle removal are discussed. Both hydrophilic and hydrophobic surfaces are considered. The flow distributions,especially the front edge expanding upon impact at microscale,strongly depend on surface wettability. The associated hydrodynamic forces on the particles vary accordingly. In addition, the impact on a dry surface can produce higher removal efficiency than that on a wet surface. Under the same impact conditions, the drag force exerted on a particle residing on a dry surface can be three orders of magnitudes larger than on a wet surface. Improving droplet impact velocity is more effective than improving droplet size.
基金Project supported by the Hi-Tech Research and Development Program (863) of China (No. 2002AA601320) the Shandong Environment Protection Bureau Program (No. 2006032, 2006043)the Ph.D Fund of Shandong Jianzhu University (No. 624006, 2006043).
文摘The particle characterization from the influent and effluent of a chemical-biological flocculation （CBF） process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatment （CEPT） process and a primary sediment tank process were also analyzed for comparison. The results showed that CBF process was not only effective for both the big size particles and small size particles removal, but also the best particle removal process in the three processes. The results also indicated that CBF process was superior to CEPT process in the heavy metals removal. The high and non-selective removal for heavy metals might be closely related to its strong ability to eliminate small particles. Samples from different locations in CBF reactors showed that small particles were easier to aggregate into big ones and those disrupted flocs could properly flocculate again along CBF reactor because of the biological flocculation.
基金the Chinese Nature Science Funds, contract! No.1988504.
文摘The ICRF (Ion Cyclotron Range Frequency) cleaning technique has been used as a routine wall cleaning method in the HT-7 superconducting tokamak. In a wide range of toroidal field, the removal rate of residual gas by ICRF cleaning was about twenty times higher than that of glow discharge cleaning (GDC). At different gas pressure and RF power levels, the ICRF cleaning is studied carefully. A good impurity cleaning effect and a very high hydrogen removal rate were obtained. The removal rate of hydrogen by 5 kW ICRF cleaning achieved was 1.6 × 10-5 Tirr.1/s.And the relationships among pressure P, outgassing rate Q, atomic layers L absorbed on surface and the cleaning mode were discussed briefly.
基金Research Project of Marine Design and Research Institute of China。
文摘Negative air ions(NAIs)in indoor environments have been suggested to positively impact human health by effectively reducing particulate contamination and gaseous pollutants,as well as inhibiting the growth of microorganisms,bacteria and viruses.This study investigates the common ionizers with different module types,and the mechanism of NAIs for enhancing indoor air quality,as well as the positive and negative impacts on human health.The association between NAI concentrations and human health outcomes is examined,and alternative measures to balance beneficial and unavailing effects are investigated.While NAIs demonstrate efficacy in removing particulate pollutants,alleviating depression,enhancing cognitive function and even stimulating sympathetic activity,it is pertinent to acknowledge the presence of contradictory findings concerning their effects on cardiac autonomic function and respiratory physiology.To address this complexity,it is imperative to consider alternative measures that strike a balance between the beneficial and unavailing effects of NAIs.These measures can encompass a general assessment of the characteristics of particulate pollutants,a strategic selection of ionizer technologies,and adherence to the recommended optimal concentration thresholds of NAIs.
基金Supported by the Application Research Project of Post-Doctoral Researchers in Qingdao(No.ZQ51201415037)the Modern Agriculture Industry System Construction of Special Funds(No.CARS-50-G10)+1 种基金the Special Project about Independent Innovation and Achievement Transformation of Shandong Province(No.2014ZZCX07102)the Key R&D Program of Jiangsu Province(No.BE2015328)
文摘A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, the discrete phase model （DPM） was applied to generate particle trajectories, and the governing equations are solved using the finite volume method. To validate this model, the numerical results were compared with data obtained from a full-scale physical model. The results show that： （1） the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks, giving an average relative error of velocities between simulated and measured values of 18% from contour maps of velocity magnitudes; （2） the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank. The average relative error of the removal rates between simulated and measured values was 11%. The DPM can be used to assess the self-cleaning capability of an octagonal tank; （3） a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations. The velocity distribution was uniform with an average velocity of 15 cm/s; the velocity reached 0.8 m/s near the inlet pipe, which can result in energy losses and cause wall abrasion; the velocity in tank corners was more than 15 cm/s, which suggests good water mixing, and there was no particle sedimentation. The percentage of particle removal for octagonal tanks was 90% with the exception of a little accumulation of 〈5 mm particle in the area between the inlet pipe and the wall. This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.
基金Project supported by the Specific Project Items No.2 in National Long-Term Technology Development Plan(No.2009zx02308-003)
文摘The effect of a non-ionic surfactant on particles removal in post-CMP cleaning was investigated. By changing the concentration of the non-ionic surfactant, a series of experiments were performed on the 12 inch Cu pattern wafers in order to determine the best cleaning results. Then the effect of the surfactant on the reduction of defects and the removal of particles was discussed in this paper. What is more, the negative effect of a non-ionic surfactant was also discussed. Based on the experiment results, it is concluded that the non-ionic surfactant could cause good and ill effects at different concentrations in the post-CMP cleaning process. This understanding will serve as a guide to how much surfactant should be added in order to achieve excellent cleaning performance.
基金supported by the National Natural Science Foundation of China(Grant No.51205006)the Tribology Science Fund of State Key Laboratory of Tribology and the Program for Excellent Talents by the Beijing Ministry of Organization
文摘Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velocimetry(PTV)technique was employed to characterize the particle removal displacement and velocity in the interface between a transparent copper film and a porous polyvinyl alcohol(PVA)brush during the cleaning process.Several different cleaning conditions including rotation speeds,loading pressure and cleaning agent were examined and the particle removal rate was compared.Elastic and friction removal,hydrodynamic removal and mixed-type removal are the three types of particle removal.Particles with an arc trace and uniform velocity curves were removed by friction and elastic force which were related to the brush load.Particles with a random trace and fluctuant velocity curves were removed by hydrodynamic force which was determined by the brush rotation speed.The increase of particle removal rate(PRR)with brush rotation speed is a logistic function.It is easier to improve PRR by increasing the brush load or by adding surfactant than by increasing the brush rotation speed.
基金supported by the National Natural Science Foundation of China(Grant Nos.51222501 and 51221004)the Fundamental Research Funds for the Central Universities
文摘In the paper,the behavior of the particle acted by the oscillating bubble is studied using a high-speed video camera.The bubble is generated using a very low voltage of 55 V.Images are captured at a speed of 15000 fps(frames per second).It is found that the velocity of the particle is dependent on the liquid viscosity,particle size,and tube diameter.Particle velocity decreases with the increase of the glycron-water mixture viscosity.A model is presented to predict the velocity and verified by experimental results.These observations may be beneficial for the application in medical treatment.
