Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HA...Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HAp and BG to dissolve and promote osseointegration,considering that both phases have different reaction and dissolution rates under in-vitro conditions.In the present work,75%wt.HAp-25%wt.S53P4 bioactive glass powders were HVOF-sprayed to obtain HAp/S53P4 BG composite coatings on a bioresorbable AZ31 alloy.The study is focused on exploring the effect of the stand-off distance and fuel/oxygen ratio variation as HVOF parameters to obtain stable structural coatings and to establish their effect on the phases and microstructure produced in those coatings.Different characterization techniques,such as scanning electron microscopy,X-ray diffraction,and Fourier transform infrared spectroscopy,were employed to characterize relevant structural and microstructural properties of the composite coatings.The results showed that thermal gradients during coating deposition must be managed to avoid delamination due to the high temperature achieved(max 550℃)and the differences in coefficients of thermal expansion.It was also found that both spraying distance and oxygen/fuel ratio allowed to keep the hydroxyapatite as the main phase in the coatings.In addition,in-vitro electrochemical studies were performed on the obtained HAp/S53P4 BG composite coatings and compared against the uncoated AZ31 alloy.The results showed a significant decrease in hydrogen evolution(at least 98%)when the bioactive coating was applied on the Mg alloy during evaluation in simulated body fluid(SBF).展开更多
During the decommissioning of the Fukushima Daiichi nuclear power plant,it is important to consider the retrieval of resolidified debris both in air and underwater configurations.For the subsequent retrieval of debris...During the decommissioning of the Fukushima Daiichi nuclear power plant,it is important to consider the retrieval of resolidified debris both in air and underwater configurations.For the subsequent retrieval of debris from the reactor building,the resolidified debris must be cut into smaller pieces using various cutting methods.During the cutting process,aerosol particles are expected to be generated at the submicron scale.It has been noted that such aerosols sizing within the Greenfield gap(0.1-1μm)are difficult to remove effectively using traditional spraying methods.Therefore,to improve the aerosol removal efficiency of the spray system,a new aerosol agglomeration method was recently proposed,which involves injecting water mist to enlarge the sizes of the aerosol particles before removing them using water sprays.In this study,a series of experiments were performed to clarify the proper spray configurations for effective aerosol scavenging and to improve the performance of the water mist.The experimental results showed that the spray flow rate and droplet characteristics are important factors for the aerosol-scavenging efficiency and performance of the water mist.The results obtained from this study will be helpful for the optimization of the spray system design for effective aerosol scavenging during the decommissioning of the Fukushima Daiichi plant.展开更多
The current study focuses on spray cooling applied to the heat exchange components of a cooling tower.An optimization of such processes is attempted by assessing different spray flow rates and droplet sizes.For simpli...The current study focuses on spray cooling applied to the heat exchange components of a cooling tower.An optimization of such processes is attempted by assessing different spray flow rates and droplet sizes.For simplicity,the heat exchanger of the cooling tower is modeled as a horizontal round tube and a cooling tower spray cooling model is developed accordingly using a computational fluid dynamics(CFD)software.The study examines the influence of varying spray flow rates and droplet sizes on the heat flow intensity between the liquid layer on the surface of the cylindrical tube and the surrounding air,taking into account the number of nozzles.It is observed that on increasing the spray flow strength,the heat flow intensity and extent of the liquid film in the system are enhanced accordingly.Moreover,the magnitude of droplet size significantly impacts heat transfer.A larger droplet size decreases evaporation in the air and enhances the deposition of droplets on the round tube.This facilitates the creation of the liquid film and enhances the passage of heat between the liquid film and air.Increasing the number of nozzles,while maintaining a constant spray flow rate,results in a decrease in the flow rate of each individual nozzle.This decrease is not favorable in terms of heat transfer.展开更多
[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the flo...[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the floating balls. [Methods] The effects of the types and amounts of isocyanate, chain extenders and polyether polyols on the gelation rate, adhesion and wear resistance of polyurea elastomer were investigated, and it was finally determined the preparation process of polyurea elastomer using liquid isophorone diisocyanate (IPDI) and amino-terminated polyether (D2000) as the main raw materials, dimethylthiotoluene diamine (E300) as the chain extender and silica as the wear resistance modifier through two-step solution polymerization of prepolymerization and chain extension. [Results] The physical properties and chemical resistance tests of spray polyurea elastomer showed that it had good physical properties and acid and alkali resistance, and could meet the requirements of spraying and protection of EPS floating ball surface in marine environment. [Conclusions] Polyurea elastomer coating can improve the aging resistance, wear resistance and acid and alkali resistance of EPS floating balls, and prevent them from being fragile and floating randomly to form marine floating garbage which results in "white pollution".展开更多
Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, survei...Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, surveillance, and firefighting. Such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating spray rails on hulls. This research paper is dedicated to a comprehensive investigation into the potential utilization of spray rails to enhance the takeoff performance of amphibian aircraft. Several spray rail configurations obtained from naval research were simulated on a bare Seamax M22 amphibian hull to observe an approximate 10% - 25% decrease in water resistance at high speeds alongside a 3% reduction in the takeoff time. This study serves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.展开更多
In this paper,we introduce the design principle of the oscillating excited spray cooling experimental device.We then designed an oscillating excited spray cooling experimental device.By using the device,the swaying mo...In this paper,we introduce the design principle of the oscillating excited spray cooling experimental device.We then designed an oscillating excited spray cooling experimental device.By using the device,the swaying motion can be realized through the control system,and the motion of the droplet under different vibration frequencies can be observed.By measuring the liquid flow rate and pressure,the changes in liquid flow rate,pressure,and temperature with time under different vibration frequencies were studied.The trajectory of the droplet and the temperature distribution of the droplet under different vibration frequencies could be observed.The device has a simple structure,is easy to control,and can achieve continuous observation of the spray cooling process.展开更多
为获得高层建筑围护结构设计风荷载,通常需要考虑其表面风压系数的概率特征,进而进行极值估计。针对当前基于超越阈值模型的风压系数极值估计方法存在阈值选取困难,需要较大样本的不足,基于高层建筑标准模型进行风洞试验,首先研究其表...为获得高层建筑围护结构设计风荷载,通常需要考虑其表面风压系数的概率特征,进而进行极值估计。针对当前基于超越阈值模型的风压系数极值估计方法存在阈值选取困难,需要较大样本的不足,基于高层建筑标准模型进行风洞试验,首先研究其表面风压系数的概率特征,结果表明迎风区测点接近高斯分布,分离区测点风压系数母体接近Gamma分布,风压系数极小值接近GEV(general extreme value,GEV)分布;提出一种改进的POT(peak over threshold,POT)极值估计方法进行表面风压系数极值估计,进而与几种传统极值估计方法进行对比,结果表明改进POT极值估计方法可实现小样本的风压系数极值估计,其估计结果与大样本容量的标准极值偏差小于5%,且稳定性较好;最后给出了标准高层建筑模型表面极值风压系数。展开更多
The failure of zinc pot hardware in continuous hot-dip galvanizing lines (CGLs) is due to zinc corrosion, abrasion ,and dross build-up. Enhancing the life of pot hardware will not only upgrade the quality of the she...The failure of zinc pot hardware in continuous hot-dip galvanizing lines (CGLs) is due to zinc corrosion, abrasion ,and dross build-up. Enhancing the life of pot hardware will not only upgrade the quality of the sheet products but also will increase the efficiency of CGLs, with decreasing cost and increasing energy savings. This paper introduces the current research and development for thermal spray coatings for pot rolls, sleeves, and bushings, and analyses the thermal spray and surface treatment technique details of dross adhesion prevention. It provides the potential applications and developing trends in thermal spray coatings and surface treatment techniques for pot hardware.展开更多
Objective] The aim was to explain the accumulation characteristic of mineral elements in alpine grassland plants and the effect of supplementary supply on the nutrient changes of mineral elements. [Method] Potted Poa ...Objective] The aim was to explain the accumulation characteristic of mineral elements in alpine grassland plants and the effect of supplementary supply on the nutrient changes of mineral elements. [Method] Potted Poa crymophila cv. Qinghai plants were regularly applied with liquid mineral mixed fertilizers, and samples were collected for analysis and detection. [Result] After the regular spraying of liquid mineral mixed fertilizers, the mineral elements in potted P. crymophila and its soil reduced ( P 〈0.05), but the accumulation of corresponding mineral elements of P. crymophila in the control group was increased due to the "Starvation Effect", which was one of the endogenetic forces driving the increase in the accumulation of mineral elements. [Conclusion] This study is of great significance for the study of the accumulation of mineral elements in degraded grassland plants and its dynamic mechanism, as well as testing the hypothesis of the Starvation Effect of mineral elements. In addition, it also provides scientific bases and technical support for the restoration and remediation of degraded grassland and the development of ecological livestock husbandry.展开更多
A method combining computationalfluid dynamics(CFD)and an analytical approach is proposed to develop a prediction model for the variable thickness of the spray-induced liquidfilm along the surface of a cylindrical workp...A method combining computationalfluid dynamics(CFD)and an analytical approach is proposed to develop a prediction model for the variable thickness of the spray-induced liquidfilm along the surface of a cylindrical workpiece.The numerical method relies on an Eulerian-Eulerian technique.Different cylinder diameters and positions and inclinations of the spray gun are considered and useful correlations for the thickness of the liquidfilm and its distribution are determined using various datafitting algorithms.Finally,the reliability of the pro-posed method is verified by means of experimental tests where the robot posture is changed.The provided cor-relation are intended to support the optimization of spray-based coating applications.展开更多
To improve the efficiency of fetching and transplanting seedlings for the mechanization of strawberry planting,an integrated transplanting mechanism was designed with protruding,fetching and planting performance to ac...To improve the efficiency of fetching and transplanting seedlings for the mechanization of strawberry planting,an integrated transplanting mechanism was designed with protruding,fetching and planting performance to achieve rapid fetching and pushing bowl movements.According to the working principle of the slewing mechanism,a kinematics model and the optimization goal were established,respectively.Based on visual auxiliary analysis software,optimal parameters were obtained.A three-dimensional model was established to obtain a simulation trajectory by means of a virtual simulation design analysis.Three-dimensional printing technology was used to manufacture the test prototype,and the actual working trajectories of the test prototype were extracted using high-speed photography technology,which verified the consistency of the actual trajectory with the theoretical and simulated trajectories.A prototype transplanting experiment was performed with the success rate of seedling extraction of 91.2%and excellent planting rate of 82.8%,which met the requirements for integrated strawberry harvesting,planting and transplanting.The experimental results verified the correctness and feasibility of the design of integrated transplanting mechanism.展开更多
Deformation can directly reflect the working behavior of the dam,so determining the deformation monitoring control value can effectively monitor the safety of dam operation.The traditional dam deformation monitoring c...Deformation can directly reflect the working behavior of the dam,so determining the deformation monitoring control value can effectively monitor the safety of dam operation.The traditional dam deformation monitoring control value only considers the single measuring point.In order to overcome the limitation,this paper presents a new method to determine the monitoring control value for concrete gravity dam based on the deformations of multi-measuring points.A dam’s comprehensive deformation displacement is determined by the measured values at different measuring points on the positive inverted vertical line and the corresponding weight of eachmeasuring point.The projection pursuit method(PPM)combined with the grey wolf optimization(GWO)algorithm is used to determine the weight of each measuring point according to the spatial correlation distribution characteristics of dam deformation.The peaks over threshold(POT)model based on the extreme value theory is adopted to determine the monitoring control value with the obtained dam comprehensive deformation displacement.In addition,the POTmodel is improved with the automatic threshold determinationmethod based on the 3σcriterion in probability theory and the GWO algorithm,which can avoid subjectivity and randomness in determining the threshold.The results of the engineering application show the feasibility and applicability of the proposed method.展开更多
The objective of this work was to elaborate ceramic water filters from Kaolinite (Cameroon) clay for the elimination of suspended particles from domestic drinking water. In Sub-Sahara Africa and in Cameroon in particu...The objective of this work was to elaborate ceramic water filters from Kaolinite (Cameroon) clay for the elimination of suspended particles from domestic drinking water. In Sub-Sahara Africa and in Cameroon in particular health issues have been linked to the consummation of domestic tap water of high turbidity values both in the rural and urban areas. In order to remedy these problems, ceramic water pot filters have been elaborated in a pilot scale unit with aim of putting in place a unit production. The chemical composition, the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses of the raw materials (clay and rice husks) was determined. The crystal phases and scanning electron microscope of Wack clay was also determined. The ceramic pot filter membranes were fabricated from the formulations 70/20/10 of clay/porogen/chamotte respectively with the particle size of the raw material less than or equal to 500 μm. The formulated ceramic pot filters were then sintered at 900˚C in a furnace. These ceramic pot filters were characterized by determining their porosity, withdrawal percentages, water permeability, mechanical and chemical resistance. The study of the efficiency consisted in evaluating the retention rate and permeate flux with respect to time (days) with synthetic water suspensions of turbidity 100 NTU and particle size of 2 μm. The ceramic pot filters were made aiming at studying the efficiency after physical defouling of filters. Physical defouling consisted in brushing the inner surface of the ceramic pot filters with water and drying them at ambient temperature after being used for 11 days and reusing them under the same initial conditions. The produced ceramic pot filter had a volume of 4 L, an average porosity of 36.15%, shrinkage in mass or withdrawal percentage of 18.23%, a water permeability of 59.6 × 10<sup>3</sup> L∙h<sup>−2</sup>∙m<sup>−</sup><sup>2</sup>, mechanical resistance of 6.8 MPa and corrosion resistance of 1.6% in acidic medium and 0.8% in alkaline medium. The evaluation of the retention efficiency reveals that the retention rate of 99.9% was obtained from the 9<sup>th</sup> day of filtration reducing the turbidity value from 100 NTU to less than 0.1 NTU. From the filtration test carried out during the 11 consecutive days, the flow rate varied between 1.46 L∙h<sup>−1</sup> to 2.63 L∙h<sup>−1</sup>. Similar results of retention and flow rate were obtained after physical defouling of the ceramic pot filter membranes and re-using for 11 consecutive days, showing the efficiency of the ceramic pot filter membranes in eliminating suspended particles from drinking water. Cost evaluation for the production unit reveals a total cost of production for 50 ceramic pot filters of 1593.6 USD consisting of fixed assets and variable assets. An estimated selling price of 3.3 USD was obtained which is affordable for both the urban and rural population in Cameroon and in sub-Saharan Africa.展开更多
Sea spray,which comprises amounts of small ocean droplets,plays a significant role in the air-sea coupling,atmospheric and oceanic dynamics,and climate.However,it remains arduous to arrive at estimates for the efficie...Sea spray,which comprises amounts of small ocean droplets,plays a significant role in the air-sea coupling,atmospheric and oceanic dynamics,and climate.However,it remains arduous to arrive at estimates for the efficiency and accuracy of the sea spray induced air-sea heat and salt fluxes.This is because the microphysical process of sea spray evolution in the air is of extreme complexity.In this study,we iteratively calculated the sea spray induced air-sea heat and salt fluxes at various weather condition.To do so,we implemented one novel wave-steepness-dependent sea spray model into a bulk air-sea fluxes algorithm and utilized other sea spray models as comparisons.Based on the improved wave-dependent bulk turbulent algorithm,we observed that despite the negative contribution of sea spray to the sensible heat fluxes,the sea spray positively contributes to the air-sea latent heat fluxes,leading to an overall increase in the total air-sea heat fluxes.The additional heat fluxes caused by sea spray may be the missing critical process that can clarify the discrepancies observed between measured and modelled Tropical Cyclone’s development and intensification.In addition to heat fluxes,we observed that sea spray has significant impacts on the air-sea salt fluxes.As the sea salt particles are one of the main sources of the atmosphere aerosol,our results imply that sea spray could impact global and regional climate.Thus,given the significance of sea spray on the air-sea boundary layer,sea spray effects need to be considered in studies of air-sea interaction,dynamics of atmosphere and ocean.展开更多
基金the National Council of Humanities,Science,and Technology(CONAHCYT)through the"Investigadores por Mexico"program,projects 848 and 881。
文摘Bioactive thermal spray coatings produced via high-velocity oxygen fuel spray(HVOF)from hydroxyapatite(HAp)and bioactive glasses(BG)have the potential to be employed on temporary implants due to the ability of both HAp and BG to dissolve and promote osseointegration,considering that both phases have different reaction and dissolution rates under in-vitro conditions.In the present work,75%wt.HAp-25%wt.S53P4 bioactive glass powders were HVOF-sprayed to obtain HAp/S53P4 BG composite coatings on a bioresorbable AZ31 alloy.The study is focused on exploring the effect of the stand-off distance and fuel/oxygen ratio variation as HVOF parameters to obtain stable structural coatings and to establish their effect on the phases and microstructure produced in those coatings.Different characterization techniques,such as scanning electron microscopy,X-ray diffraction,and Fourier transform infrared spectroscopy,were employed to characterize relevant structural and microstructural properties of the composite coatings.The results showed that thermal gradients during coating deposition must be managed to avoid delamination due to the high temperature achieved(max 550℃)and the differences in coefficients of thermal expansion.It was also found that both spraying distance and oxygen/fuel ratio allowed to keep the hydroxyapatite as the main phase in the coatings.In addition,in-vitro electrochemical studies were performed on the obtained HAp/S53P4 BG composite coatings and compared against the uncoated AZ31 alloy.The results showed a significant decrease in hydrogen evolution(at least 98%)when the bioactive coating was applied on the Mg alloy during evaluation in simulated body fluid(SBF).
基金financially supported by the Nuclear Energy Science and Technology and Human Resource Development Project of the Japan Atomic Energy Agency/Collaborative Laboratories for Advanced Decommissioning Science(No.R04I034)Ruicong Xu appreciates the scholarship(financial support)from the Chinese Scholarship Council(CSC No.202106380073).
文摘During the decommissioning of the Fukushima Daiichi nuclear power plant,it is important to consider the retrieval of resolidified debris both in air and underwater configurations.For the subsequent retrieval of debris from the reactor building,the resolidified debris must be cut into smaller pieces using various cutting methods.During the cutting process,aerosol particles are expected to be generated at the submicron scale.It has been noted that such aerosols sizing within the Greenfield gap(0.1-1μm)are difficult to remove effectively using traditional spraying methods.Therefore,to improve the aerosol removal efficiency of the spray system,a new aerosol agglomeration method was recently proposed,which involves injecting water mist to enlarge the sizes of the aerosol particles before removing them using water sprays.In this study,a series of experiments were performed to clarify the proper spray configurations for effective aerosol scavenging and to improve the performance of the water mist.The experimental results showed that the spray flow rate and droplet characteristics are important factors for the aerosol-scavenging efficiency and performance of the water mist.The results obtained from this study will be helpful for the optimization of the spray system design for effective aerosol scavenging during the decommissioning of the Fukushima Daiichi plant.
基金supported by the National Natural Science Foundation of China(Grant No.52376069)Shandong Province Science and Technology Small and Medium sized Enterprise Innovation Ability Enhancement Project(Grant No.2022TSGC2596).
文摘The current study focuses on spray cooling applied to the heat exchange components of a cooling tower.An optimization of such processes is attempted by assessing different spray flow rates and droplet sizes.For simplicity,the heat exchanger of the cooling tower is modeled as a horizontal round tube and a cooling tower spray cooling model is developed accordingly using a computational fluid dynamics(CFD)software.The study examines the influence of varying spray flow rates and droplet sizes on the heat flow intensity between the liquid layer on the surface of the cylindrical tube and the surrounding air,taking into account the number of nozzles.It is observed that on increasing the spray flow strength,the heat flow intensity and extent of the liquid film in the system are enhanced accordingly.Moreover,the magnitude of droplet size significantly impacts heat transfer.A larger droplet size decreases evaporation in the air and enhances the deposition of droplets on the round tube.This facilitates the creation of the liquid film and enhances the passage of heat between the liquid film and air.Increasing the number of nozzles,while maintaining a constant spray flow rate,results in a decrease in the flow rate of each individual nozzle.This decrease is not favorable in terms of heat transfer.
基金Supported by Special Project for High-quality Development of Marine Services and Fishery in Fujian Province in 2023(FJHY-YYKJ-2023-1-3)。
文摘[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the floating balls. [Methods] The effects of the types and amounts of isocyanate, chain extenders and polyether polyols on the gelation rate, adhesion and wear resistance of polyurea elastomer were investigated, and it was finally determined the preparation process of polyurea elastomer using liquid isophorone diisocyanate (IPDI) and amino-terminated polyether (D2000) as the main raw materials, dimethylthiotoluene diamine (E300) as the chain extender and silica as the wear resistance modifier through two-step solution polymerization of prepolymerization and chain extension. [Results] The physical properties and chemical resistance tests of spray polyurea elastomer showed that it had good physical properties and acid and alkali resistance, and could meet the requirements of spraying and protection of EPS floating ball surface in marine environment. [Conclusions] Polyurea elastomer coating can improve the aging resistance, wear resistance and acid and alkali resistance of EPS floating balls, and prevent them from being fragile and floating randomly to form marine floating garbage which results in "white pollution".
文摘Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, surveillance, and firefighting. Such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating spray rails on hulls. This research paper is dedicated to a comprehensive investigation into the potential utilization of spray rails to enhance the takeoff performance of amphibian aircraft. Several spray rail configurations obtained from naval research were simulated on a bare Seamax M22 amphibian hull to observe an approximate 10% - 25% decrease in water resistance at high speeds alongside a 3% reduction in the takeoff time. This study serves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.
基金The Natural Science Foundation of the Jiangsu Higher Education Institutions of China(22KJD580001)Jiangsu Maritime Institute Innovation Technology Funding Project(kicx2020-2)。
文摘In this paper,we introduce the design principle of the oscillating excited spray cooling experimental device.We then designed an oscillating excited spray cooling experimental device.By using the device,the swaying motion can be realized through the control system,and the motion of the droplet under different vibration frequencies can be observed.By measuring the liquid flow rate and pressure,the changes in liquid flow rate,pressure,and temperature with time under different vibration frequencies were studied.The trajectory of the droplet and the temperature distribution of the droplet under different vibration frequencies could be observed.The device has a simple structure,is easy to control,and can achieve continuous observation of the spray cooling process.
文摘为获得高层建筑围护结构设计风荷载,通常需要考虑其表面风压系数的概率特征,进而进行极值估计。针对当前基于超越阈值模型的风压系数极值估计方法存在阈值选取困难,需要较大样本的不足,基于高层建筑标准模型进行风洞试验,首先研究其表面风压系数的概率特征,结果表明迎风区测点接近高斯分布,分离区测点风压系数母体接近Gamma分布,风压系数极小值接近GEV(general extreme value,GEV)分布;提出一种改进的POT(peak over threshold,POT)极值估计方法进行表面风压系数极值估计,进而与几种传统极值估计方法进行对比,结果表明改进POT极值估计方法可实现小样本的风压系数极值估计,其估计结果与大样本容量的标准极值偏差小于5%,且稳定性较好;最后给出了标准高层建筑模型表面极值风压系数。
文摘The failure of zinc pot hardware in continuous hot-dip galvanizing lines (CGLs) is due to zinc corrosion, abrasion ,and dross build-up. Enhancing the life of pot hardware will not only upgrade the quality of the sheet products but also will increase the efficiency of CGLs, with decreasing cost and increasing energy savings. This paper introduces the current research and development for thermal spray coatings for pot rolls, sleeves, and bushings, and analyses the thermal spray and surface treatment technique details of dross adhesion prevention. It provides the potential applications and developing trends in thermal spray coatings and surface treatment techniques for pot hardware.
基金Supported by the General Program of Natural Science Foundation of Qinghai Province(2016-ZJ-906)
文摘Objective] The aim was to explain the accumulation characteristic of mineral elements in alpine grassland plants and the effect of supplementary supply on the nutrient changes of mineral elements. [Method] Potted Poa crymophila cv. Qinghai plants were regularly applied with liquid mineral mixed fertilizers, and samples were collected for analysis and detection. [Result] After the regular spraying of liquid mineral mixed fertilizers, the mineral elements in potted P. crymophila and its soil reduced ( P 〈0.05), but the accumulation of corresponding mineral elements of P. crymophila in the control group was increased due to the "Starvation Effect", which was one of the endogenetic forces driving the increase in the accumulation of mineral elements. [Conclusion] This study is of great significance for the study of the accumulation of mineral elements in degraded grassland plants and its dynamic mechanism, as well as testing the hypothesis of the Starvation Effect of mineral elements. In addition, it also provides scientific bases and technical support for the restoration and remediation of degraded grassland and the development of ecological livestock husbandry.
基金This work was supported in part by the National Natural Science Foundation of China(51405418)in part by the Major Program of Natural Science Foundation of Colleges and Universities in Jiangsu Province(18KJA460009)+2 种基金in part by the Jiangsu“Qing Lan Project”Talent Project(2021)Major Projects of Natural Science Research in Jiangsu Higher Education Institutions(Grant No.21KJA460009)General Program of Jiangsu University Natural Science Foundation(22KJD460009).
文摘A method combining computationalfluid dynamics(CFD)and an analytical approach is proposed to develop a prediction model for the variable thickness of the spray-induced liquidfilm along the surface of a cylindrical workpiece.The numerical method relies on an Eulerian-Eulerian technique.Different cylinder diameters and positions and inclinations of the spray gun are considered and useful correlations for the thickness of the liquidfilm and its distribution are determined using various datafitting algorithms.Finally,the reliability of the pro-posed method is verified by means of experimental tests where the robot posture is changed.The provided cor-relation are intended to support the optimization of spray-based coating applications.
基金Supported by the National Natural Science Foundation of China Youth Fund Project(52005221)"the 13th Five-Year"National Key Research and Development Program:High-speed Planting Technology and Equipment Research and Development(2017YFD0700800)。
文摘To improve the efficiency of fetching and transplanting seedlings for the mechanization of strawberry planting,an integrated transplanting mechanism was designed with protruding,fetching and planting performance to achieve rapid fetching and pushing bowl movements.According to the working principle of the slewing mechanism,a kinematics model and the optimization goal were established,respectively.Based on visual auxiliary analysis software,optimal parameters were obtained.A three-dimensional model was established to obtain a simulation trajectory by means of a virtual simulation design analysis.Three-dimensional printing technology was used to manufacture the test prototype,and the actual working trajectories of the test prototype were extracted using high-speed photography technology,which verified the consistency of the actual trajectory with the theoretical and simulated trajectories.A prototype transplanting experiment was performed with the success rate of seedling extraction of 91.2%and excellent planting rate of 82.8%,which met the requirements for integrated strawberry harvesting,planting and transplanting.The experimental results verified the correctness and feasibility of the design of integrated transplanting mechanism.
文摘Deformation can directly reflect the working behavior of the dam,so determining the deformation monitoring control value can effectively monitor the safety of dam operation.The traditional dam deformation monitoring control value only considers the single measuring point.In order to overcome the limitation,this paper presents a new method to determine the monitoring control value for concrete gravity dam based on the deformations of multi-measuring points.A dam’s comprehensive deformation displacement is determined by the measured values at different measuring points on the positive inverted vertical line and the corresponding weight of eachmeasuring point.The projection pursuit method(PPM)combined with the grey wolf optimization(GWO)algorithm is used to determine the weight of each measuring point according to the spatial correlation distribution characteristics of dam deformation.The peaks over threshold(POT)model based on the extreme value theory is adopted to determine the monitoring control value with the obtained dam comprehensive deformation displacement.In addition,the POTmodel is improved with the automatic threshold determinationmethod based on the 3σcriterion in probability theory and the GWO algorithm,which can avoid subjectivity and randomness in determining the threshold.The results of the engineering application show the feasibility and applicability of the proposed method.
文摘The objective of this work was to elaborate ceramic water filters from Kaolinite (Cameroon) clay for the elimination of suspended particles from domestic drinking water. In Sub-Sahara Africa and in Cameroon in particular health issues have been linked to the consummation of domestic tap water of high turbidity values both in the rural and urban areas. In order to remedy these problems, ceramic water pot filters have been elaborated in a pilot scale unit with aim of putting in place a unit production. The chemical composition, the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses of the raw materials (clay and rice husks) was determined. The crystal phases and scanning electron microscope of Wack clay was also determined. The ceramic pot filter membranes were fabricated from the formulations 70/20/10 of clay/porogen/chamotte respectively with the particle size of the raw material less than or equal to 500 μm. The formulated ceramic pot filters were then sintered at 900˚C in a furnace. These ceramic pot filters were characterized by determining their porosity, withdrawal percentages, water permeability, mechanical and chemical resistance. The study of the efficiency consisted in evaluating the retention rate and permeate flux with respect to time (days) with synthetic water suspensions of turbidity 100 NTU and particle size of 2 μm. The ceramic pot filters were made aiming at studying the efficiency after physical defouling of filters. Physical defouling consisted in brushing the inner surface of the ceramic pot filters with water and drying them at ambient temperature after being used for 11 days and reusing them under the same initial conditions. The produced ceramic pot filter had a volume of 4 L, an average porosity of 36.15%, shrinkage in mass or withdrawal percentage of 18.23%, a water permeability of 59.6 × 10<sup>3</sup> L∙h<sup>−2</sup>∙m<sup>−</sup><sup>2</sup>, mechanical resistance of 6.8 MPa and corrosion resistance of 1.6% in acidic medium and 0.8% in alkaline medium. The evaluation of the retention efficiency reveals that the retention rate of 99.9% was obtained from the 9<sup>th</sup> day of filtration reducing the turbidity value from 100 NTU to less than 0.1 NTU. From the filtration test carried out during the 11 consecutive days, the flow rate varied between 1.46 L∙h<sup>−1</sup> to 2.63 L∙h<sup>−1</sup>. Similar results of retention and flow rate were obtained after physical defouling of the ceramic pot filter membranes and re-using for 11 consecutive days, showing the efficiency of the ceramic pot filter membranes in eliminating suspended particles from drinking water. Cost evaluation for the production unit reveals a total cost of production for 50 ceramic pot filters of 1593.6 USD consisting of fixed assets and variable assets. An estimated selling price of 3.3 USD was obtained which is affordable for both the urban and rural population in Cameroon and in sub-Saharan Africa.
基金The support of the US Office of Naval Research Global under contract No.N62909-20-1-2080.
文摘Sea spray,which comprises amounts of small ocean droplets,plays a significant role in the air-sea coupling,atmospheric and oceanic dynamics,and climate.However,it remains arduous to arrive at estimates for the efficiency and accuracy of the sea spray induced air-sea heat and salt fluxes.This is because the microphysical process of sea spray evolution in the air is of extreme complexity.In this study,we iteratively calculated the sea spray induced air-sea heat and salt fluxes at various weather condition.To do so,we implemented one novel wave-steepness-dependent sea spray model into a bulk air-sea fluxes algorithm and utilized other sea spray models as comparisons.Based on the improved wave-dependent bulk turbulent algorithm,we observed that despite the negative contribution of sea spray to the sensible heat fluxes,the sea spray positively contributes to the air-sea latent heat fluxes,leading to an overall increase in the total air-sea heat fluxes.The additional heat fluxes caused by sea spray may be the missing critical process that can clarify the discrepancies observed between measured and modelled Tropical Cyclone’s development and intensification.In addition to heat fluxes,we observed that sea spray has significant impacts on the air-sea salt fluxes.As the sea salt particles are one of the main sources of the atmosphere aerosol,our results imply that sea spray could impact global and regional climate.Thus,given the significance of sea spray on the air-sea boundary layer,sea spray effects need to be considered in studies of air-sea interaction,dynamics of atmosphere and ocean.