To elucidate the adsorption characteristics and retention mechanisms of fracturing fluids in diverse clay minerals,we conducted on-line nuclear magnetic resonance(NMR)and atomic force microscopy(AFM)experiments.The de...To elucidate the adsorption characteristics and retention mechanisms of fracturing fluids in diverse clay minerals,we conducted on-line nuclear magnetic resonance(NMR)and atomic force microscopy(AFM)experiments.The depth and extent of solid phase damage are determined by the ratio between the size of fine fractions in fracturing fluid residue and the pore-throat size in experiments.Poor physical properties(K<0.5 mD)result in a more preferential flow pathway effect during flowback,and the stepwise incremental pressure differential proves to be more effective for the discharge of fracturing fluid in submicron pore throats.The permeability is significantly influenced by the differential distri-bution of retained fracturing fluid,as supported by direct experimental evidence.The presence of good physical properties(K>0.5 mD)combined with a scattered distribution of retained fracturing fluid is associated with high gas phase recovery permeability,whereas a continuous sheet-like distribution results in low recovery permeability.The expansive surface area and presence of filamentous illite minerals facilitate the multiple winding and adsorption of fracturing fluids,demonstrating strong hydrogen-bonding,multi-layering and multiple adsorption properties.The geological characteristics of the main gas formations exhibit significant variation,and the severity of damage caused by fracturing fluids occurs in diverse sequences.To address this issue,a differentiated strategy for optimizing frac-turing fluids has been proposed.展开更多
Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limitin...Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.展开更多
Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a ...Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a green bio-based flame-retardant system to fabricate polyurethane foam composite with durable flame retardancy,smoke suppression,and thermal insulation property.In this system,the green bio-based polyol(VED)with good reactivity and compatibility plays a role of flame retardant and EG acts as a synergistic filler.As a result,the LOI value of foam composite increased to 30.5 vol.%and it achieved a V-0 rating in the UL-94 vertical burning test.Additionally,the peak heat release rate(pHRR)and the total smoke production(TSP)decreased by 66.1%and 63.4%,respectively.Furthermore,the foam composite maintained durable flame retardancy after accelerated thermal aging test,whose thermal-insulating property was maintained even after being treated in high-humidity environment with 85%R.H.for a week.This work provides a facile strategy for durable flame retardancy and long-term thermal insulation performance,and creates opportunities for the practical applications of bio-based foam composites.展开更多
CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the...CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.展开更多
Micro milling has many advantages in fabricating three-dimensional(3D) structure in micrometer scale. The micro milling machine tool with high positioning accuracy is of great importance for getting micro structure wi...Micro milling has many advantages in fabricating three-dimensional(3D) structure in micrometer scale. The micro milling machine tool with high positioning accuracy is of great importance for getting micro structure with high profile precision and good surface quality. Meanwhile, the method of position error compensation is a good way to improve the accuracy of the micro milling machine tools. In this paper,a software method is adopted to compensate the positioning error and improve the positioning accuracy. According to error cancellation theory,the compensation values are generated and compensation tables are built to adjust the positioning error in the NC system based on Industrial Motion and Automation Control( IMAC). The positioning accuracy of linear motor is ± 0. 3 μm without backlash after compensation. In order to verify the effectiveness of compensation on the machining performance,concave spherical surfaces are processed on the micro milling machine tool. The experimental results show that the profile radius error of the spherical surface machined with compensation decreases more than 60%.展开更多
Objective： To evaluate the effect of different training methods of Tai Chi on Chinese medicine constitution of international students with depression or depression tendency. Methods： Thirty-eight Africa internatio...Objective： To evaluate the effect of different training methods of Tai Chi on Chinese medicine constitution of international students with depression or depression tendency. Methods： Thirty-eight Africa international students were randomly divided into the physical exercise group who receiving the simple physical exercise of simplified 24-form Tai Chi （physical exercise group） and the breathing group who receiving both deep breathing method plus simple physical exercise （breathing group）. The average scores of Chinese medicine gentleness and various biased constitutional types in the two groups were compared. Results： The average score of thirty-eight students with biased constitution in both groups decreased significantly compared with that before training （P 〈 0.05）. Compared with that before training, the average scores of biased constitutional types in the breathing group, including Qi deficiency, Yang deficiency, phlegm-dampness and Qi stagnation, were significantly decreased （P 〈 0.05）. The average scores of Yang deficiency, blood stasis and Qi stagnation constitutional types of students in simple physical group after training were also significantly decreased after training （P 〈 0.05）. Moreover, the average scores of biased constitutional types, including Qi deficiency, Yang deficiency, Yin deficiency, phlegm and dampness, Qi-stagnation, in the breathing group were significantly lower than those of the simple exercise group, suggesting the superior therapeutic effect of breathing training method （P 〈 0.01）. Conclusion： When combines with the deep breathing method, Tai Chi training achieves better effect on improving the biased constitutional types which may be related to depression or depression tendency, including Qi deficiency, Yang deficiency, Yin deficiency, phlegm and dampness, Qi-stagnation.展开更多
Aerogels,as competitive thermal insulating sub-stitutes,are seriously plagued by the deterioration of mechanical and insulating properties at high temperatures as well as energy-consuming drying methods.Herein,organic...Aerogels,as competitive thermal insulating sub-stitutes,are seriously plagued by the deterioration of mechanical and insulating properties at high temperatures as well as energy-consuming drying methods.Herein,organic-inorganic biomass composite aerogels with ablative properties are fabricated by a straightforward and environmentally friendly ambient-pressure-dried method,utilizing gellan gum,hollow glass microspheres,and phenolic resin.This method uses air bubbles as pore templates for constructing aerogels without additional modification or organic solvent consumption.The robust cross-linking networks formed within the aerogels significantly mitigate volume shrinkage induced by surface tension during mild drying while endowing the aerogels with a high modulus of 37.8 MPa and robust resistance to diverse rigors.Remarkably,upon exposure to high temperatures or fire,it spontaneously transforms into ceramic-like hybrid char with low volume shrinkage,continuous pore structures,and high stability.The ablative property of these aerogels enables them to maintain a high modulus of 8.22 MPa even after being treated at 900℃,while also exhibiting excellent high-temperature insulation,flame retardance,and smoke suppression.This work provides a facile and ecofriendly way for developing advanced hybrid biomass aerogels that combine high stiffness with superior thermal protection across a wide temperature range.展开更多
The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO con...The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO consists of 1.3 km^(2) array(KM2A)of electromagnetic particle detectors(ED)and muon detectors(MD),a water Cherenkov detector array(WCDA)with a total active area of 78,000 m^(2),18 wide field-of-view air Cherenkov telescopes(WFCTA)and a newly proposed electron-neutron detector array(ENDA)covering 10,000 m^(2).Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol.The observatory includes an IT center which comprises the data acquisition system and trigger system,the data analysis facility.In this Chapter,all the above-mentioned components of LHAASO as well as infrastructure are described.展开更多
Introduction The Large High Altitude Air Shower Observatory(LHAASO)will be constructed at Mt.Haizishan,Sichuan Province,China.Among several detector components of the LHAASO,the Water Cherenkov Detector Array(WCDA)is ...Introduction The Large High Altitude Air Shower Observatory(LHAASO)will be constructed at Mt.Haizishan,Sichuan Province,China.Among several detector components of the LHAASO,the Water Cherenkov Detector Array(WCDA)is of great importance for gamma-ray astronomy from 100 GeV to 30 TeV.The single-channel counting rate of a photo-multiplier tube can reach as high as 30-35 kHz,most of them are background noise hits from the low energy cosmic ray showers,bringing a big challenge on data transferring,data storage and event reconstruction.Methods In this paper,a dedicated trigger scheme and a fast noise filtering method aiming to deal with these high rate background noise hits are introduced.These methods are tested with some Monte Carlo simulation data,showing a fair efficiency in filtering background noise hits,while most of the real shower signals are kept.Conclusion This method is proposed to be applied in a stage of the online processing just after the data are acquired in LHAASO-WCDA.展开更多
基金supported by the Sichuan Youth Science and Technology Innovation Research Team Project(No.2021JDTDO017)the open Fund(PLN2022-11)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)+1 种基金Southwest Petroleum University Graduate Innovation Fund(No.2022KYCX021)Jian Tian would like to acknowledge the funding from the National Natural Science Foundation of China(52404023).
文摘To elucidate the adsorption characteristics and retention mechanisms of fracturing fluids in diverse clay minerals,we conducted on-line nuclear magnetic resonance(NMR)and atomic force microscopy(AFM)experiments.The depth and extent of solid phase damage are determined by the ratio between the size of fine fractions in fracturing fluid residue and the pore-throat size in experiments.Poor physical properties(K<0.5 mD)result in a more preferential flow pathway effect during flowback,and the stepwise incremental pressure differential proves to be more effective for the discharge of fracturing fluid in submicron pore throats.The permeability is significantly influenced by the differential distri-bution of retained fracturing fluid,as supported by direct experimental evidence.The presence of good physical properties(K>0.5 mD)combined with a scattered distribution of retained fracturing fluid is associated with high gas phase recovery permeability,whereas a continuous sheet-like distribution results in low recovery permeability.The expansive surface area and presence of filamentous illite minerals facilitate the multiple winding and adsorption of fracturing fluids,demonstrating strong hydrogen-bonding,multi-layering and multiple adsorption properties.The geological characteristics of the main gas formations exhibit significant variation,and the severity of damage caused by fracturing fluids occurs in diverse sequences.To address this issue,a differentiated strategy for optimizing frac-turing fluids has been proposed.
基金financially supported by the National Natural Science Foundation of China(Nos.50933005 and 51121001)the Program for Changjiang Scholars and Innovative Research Teams in Universities of China(IRT 1026)
文摘Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.
基金supported by the National Natural Science Foundation of China(Nos.22175123,52122302,and 51991351)the 111 Project(No.B20001)Fundamental Research Funds for the Central Universities,and Open and Innovative Fund of Hubei Three Gorges Laboratory(Nos.2022LF2021 and SC213011).
文摘Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a green bio-based flame-retardant system to fabricate polyurethane foam composite with durable flame retardancy,smoke suppression,and thermal insulation property.In this system,the green bio-based polyol(VED)with good reactivity and compatibility plays a role of flame retardant and EG acts as a synergistic filler.As a result,the LOI value of foam composite increased to 30.5 vol.%and it achieved a V-0 rating in the UL-94 vertical burning test.Additionally,the peak heat release rate(pHRR)and the total smoke production(TSP)decreased by 66.1%and 63.4%,respectively.Furthermore,the foam composite maintained durable flame retardancy after accelerated thermal aging test,whose thermal-insulating property was maintained even after being treated in high-humidity environment with 85%R.H.for a week.This work provides a facile strategy for durable flame retardancy and long-term thermal insulation performance,and creates opportunities for the practical applications of bio-based foam composites.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51775147 and 51705105)the Science Challenge Project of China(Grant No.TZ2016006-0503-01)+2 种基金the Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001)the China Postdoctoral Science Foundation funded project(Grant Nos.2018T110288 and 2017M621260)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant Nos.SKLRS201718A and SKLRS201803B).
文摘CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50935003)
文摘Micro milling has many advantages in fabricating three-dimensional(3D) structure in micrometer scale. The micro milling machine tool with high positioning accuracy is of great importance for getting micro structure with high profile precision and good surface quality. Meanwhile, the method of position error compensation is a good way to improve the accuracy of the micro milling machine tools. In this paper,a software method is adopted to compensate the positioning error and improve the positioning accuracy. According to error cancellation theory,the compensation values are generated and compensation tables are built to adjust the positioning error in the NC system based on Industrial Motion and Automation Control( IMAC). The positioning accuracy of linear motor is ± 0. 3 μm without backlash after compensation. In order to verify the effectiveness of compensation on the machining performance,concave spherical surfaces are processed on the micro milling machine tool. The experimental results show that the profile radius error of the spherical surface machined with compensation decreases more than 60%.
文摘Objective： To evaluate the effect of different training methods of Tai Chi on Chinese medicine constitution of international students with depression or depression tendency. Methods： Thirty-eight Africa international students were randomly divided into the physical exercise group who receiving the simple physical exercise of simplified 24-form Tai Chi （physical exercise group） and the breathing group who receiving both deep breathing method plus simple physical exercise （breathing group）. The average scores of Chinese medicine gentleness and various biased constitutional types in the two groups were compared. Results： The average score of thirty-eight students with biased constitution in both groups decreased significantly compared with that before training （P 〈 0.05）. Compared with that before training, the average scores of biased constitutional types in the breathing group, including Qi deficiency, Yang deficiency, phlegm-dampness and Qi stagnation, were significantly decreased （P 〈 0.05）. The average scores of Yang deficiency, blood stasis and Qi stagnation constitutional types of students in simple physical group after training were also significantly decreased after training （P 〈 0.05）. Moreover, the average scores of biased constitutional types, including Qi deficiency, Yang deficiency, Yin deficiency, phlegm and dampness, Qi-stagnation, in the breathing group were significantly lower than those of the simple exercise group, suggesting the superior therapeutic effect of breathing training method （P 〈 0.01）. Conclusion： When combines with the deep breathing method, Tai Chi training achieves better effect on improving the biased constitutional types which may be related to depression or depression tendency, including Qi deficiency, Yang deficiency, Yin deficiency, phlegm and dampness, Qi-stagnation.
基金support by the National Natural Science Foundation of China(22205184,U22A20150,and 22475177)the Sichuan Science and Technology Program(2023NSFSC1955)+1 种基金the Hunan Provincial Key Research and Development Program(2023GK2090)the Hunan Provincial Science and Technology Innovation Program Project(2022RC1079)are sincerely acknowledged.
文摘Aerogels,as competitive thermal insulating sub-stitutes,are seriously plagued by the deterioration of mechanical and insulating properties at high temperatures as well as energy-consuming drying methods.Herein,organic-inorganic biomass composite aerogels with ablative properties are fabricated by a straightforward and environmentally friendly ambient-pressure-dried method,utilizing gellan gum,hollow glass microspheres,and phenolic resin.This method uses air bubbles as pore templates for constructing aerogels without additional modification or organic solvent consumption.The robust cross-linking networks formed within the aerogels significantly mitigate volume shrinkage induced by surface tension during mild drying while endowing the aerogels with a high modulus of 37.8 MPa and robust resistance to diverse rigors.Remarkably,upon exposure to high temperatures or fire,it spontaneously transforms into ceramic-like hybrid char with low volume shrinkage,continuous pore structures,and high stability.The ablative property of these aerogels enables them to maintain a high modulus of 8.22 MPa even after being treated at 900℃,while also exhibiting excellent high-temperature insulation,flame retardance,and smoke suppression.This work provides a facile and ecofriendly way for developing advanced hybrid biomass aerogels that combine high stiffness with superior thermal protection across a wide temperature range.
基金Supported by National Natural Science Foundation in China(NSFC)(U2031103,U1831208,11805209,11775233)NSFC for Distinguished Young Scholars(12025502)+1 种基金the Science and Technology Department of Sichuan Province(2021YFSY0031)the International Partnership Program of Chinese Academy of Sciences(113111KYSB20170055)。
文摘The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO consists of 1.3 km^(2) array(KM2A)of electromagnetic particle detectors(ED)and muon detectors(MD),a water Cherenkov detector array(WCDA)with a total active area of 78,000 m^(2),18 wide field-of-view air Cherenkov telescopes(WFCTA)and a newly proposed electron-neutron detector array(ENDA)covering 10,000 m^(2).Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol.The observatory includes an IT center which comprises the data acquisition system and trigger system,the data analysis facility.In this Chapter,all the above-mentioned components of LHAASO as well as infrastructure are described.
基金This work is supported in China by NSFC(No.11675187,No.11375224,No.11635011)the Key Laboratory of Particle Astrophysics,Chinese Academy of Sciences.
文摘Introduction The Large High Altitude Air Shower Observatory(LHAASO)will be constructed at Mt.Haizishan,Sichuan Province,China.Among several detector components of the LHAASO,the Water Cherenkov Detector Array(WCDA)is of great importance for gamma-ray astronomy from 100 GeV to 30 TeV.The single-channel counting rate of a photo-multiplier tube can reach as high as 30-35 kHz,most of them are background noise hits from the low energy cosmic ray showers,bringing a big challenge on data transferring,data storage and event reconstruction.Methods In this paper,a dedicated trigger scheme and a fast noise filtering method aiming to deal with these high rate background noise hits are introduced.These methods are tested with some Monte Carlo simulation data,showing a fair efficiency in filtering background noise hits,while most of the real shower signals are kept.Conclusion This method is proposed to be applied in a stage of the online processing just after the data are acquired in LHAASO-WCDA.
