The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of r...The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of reactions depends on the reactive activities of raw materials, initial composition of mixture and relative activity of SiO_2 and A12O3. The hydrothermal reaction can be accelerated by sodium hydroxide,in the case of silica,which has low activity, this is quite obvious.展开更多
Karst environment is very common in southwest China. Soil and vegetation are the most sensitive elements for the variation of karst environment. The weathering of carbonate is important soil formation mechanism in kar...Karst environment is very common in southwest China. Soil and vegetation are the most sensitive elements for the variation of karst environment. The weathering of carbonate is important soil formation mechanism in karst area, but its soil forming ability is so poor that the thickness of soil layer becomes thin by the water erosion, though the soil loss is insignificant but serious. The karst process, the ecology process, the hydrology process are three important circulation mechanisms in the karst multiple media environment. In the Chinese North and South karst area, the eco-environmental protection and restoration has already been the important part as the national territorial resources and the environmen- tal comprehensive development and management. The character of karst plants mainly depends on the environmental conditions, i.e. lack of water, richness of Ca, poor soil and shortage of organic matter. The plants have low growth pace and low life-form resource; it is vulnerable under the disturbance of irrational human activities. Therefore, the rocky desertification is the final result of karst ecosystem degradation. But ecological condition is severe in the North and South karst area, especially in the south karst stone mountainous area and the north arid karst area. There are many problems with the eco-environmental protection and restoration. This paper takes the karst multiple media environment as a core, comprehensively discusses the relations of the three processes – karst, hydrology, and ecology, and puts forward the direction of the research on karst ecology hydrology and the future.展开更多
Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring ...Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring and remote operation,offering users high level of safety,convenience and comfort.Moreover,noncontact sensing is ideal to maximize the immersive user experience in the human–machine interaction(HMI),eliminating interference to human activities and mechanical fatigue to the sensor,simultaneously.Herein,we report a self-powered flexible sensor integrated with irradiation cross-linked polypropylene(IXPP)piezoelectret film for noncontact sensing,featuring multi-functions to detect mechanical signals transmitted through solid,liquid and gaseous media and would facilitate their versatile practical applications.The folded-structure configuration of the sensor facilitates the improvement of the noncontact sensing sensitivity.For solid media,such as the rectangular wooden stick used in this study,the sensor can detect mechanical stimulus exerted at a distance of 100 cm.A system detection sensitivity up to 57 pC/kPa with a low detection limit of 0.6 kPa is achieved at a noncontact distance of 10 cm.Even when partly or completely immersed in water,the sensor effectively traces movement signals of human bodies underwater,demonstrating great advantages for non-inductive aquatic fitness training monitoring.Furthermore,due to the low acoustic impedance of piezoelectret film,speech recognition through gaseous medium is also achieved.We further introduce application demonstrations of the developed film sensors to monitor exercise postures and physiological signals without direct contact between human body and the sensor,displaying great potential to be incorporated into future smart electronics.This study commendably expands the application scope of piezoelectret materials,which will have profound implications for exploring novel intelligent human–machine interactions.展开更多
Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive ...Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.展开更多
基金National H-Tech Program under contract 863-7152101
文摘The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of reactions depends on the reactive activities of raw materials, initial composition of mixture and relative activity of SiO_2 and A12O3. The hydrothermal reaction can be accelerated by sodium hydroxide,in the case of silica,which has low activity, this is quite obvious.
文摘Karst environment is very common in southwest China. Soil and vegetation are the most sensitive elements for the variation of karst environment. The weathering of carbonate is important soil formation mechanism in karst area, but its soil forming ability is so poor that the thickness of soil layer becomes thin by the water erosion, though the soil loss is insignificant but serious. The karst process, the ecology process, the hydrology process are three important circulation mechanisms in the karst multiple media environment. In the Chinese North and South karst area, the eco-environmental protection and restoration has already been the important part as the national territorial resources and the environmen- tal comprehensive development and management. The character of karst plants mainly depends on the environmental conditions, i.e. lack of water, richness of Ca, poor soil and shortage of organic matter. The plants have low growth pace and low life-form resource; it is vulnerable under the disturbance of irrational human activities. Therefore, the rocky desertification is the final result of karst ecosystem degradation. But ecological condition is severe in the North and South karst area, especially in the south karst stone mountainous area and the north arid karst area. There are many problems with the eco-environmental protection and restoration. This paper takes the karst multiple media environment as a core, comprehensively discusses the relations of the three processes – karst, hydrology, and ecology, and puts forward the direction of the research on karst ecology hydrology and the future.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.62201392,12174061 and 12374451).
文摘Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring and remote operation,offering users high level of safety,convenience and comfort.Moreover,noncontact sensing is ideal to maximize the immersive user experience in the human–machine interaction(HMI),eliminating interference to human activities and mechanical fatigue to the sensor,simultaneously.Herein,we report a self-powered flexible sensor integrated with irradiation cross-linked polypropylene(IXPP)piezoelectret film for noncontact sensing,featuring multi-functions to detect mechanical signals transmitted through solid,liquid and gaseous media and would facilitate their versatile practical applications.The folded-structure configuration of the sensor facilitates the improvement of the noncontact sensing sensitivity.For solid media,such as the rectangular wooden stick used in this study,the sensor can detect mechanical stimulus exerted at a distance of 100 cm.A system detection sensitivity up to 57 pC/kPa with a low detection limit of 0.6 kPa is achieved at a noncontact distance of 10 cm.Even when partly or completely immersed in water,the sensor effectively traces movement signals of human bodies underwater,demonstrating great advantages for non-inductive aquatic fitness training monitoring.Furthermore,due to the low acoustic impedance of piezoelectret film,speech recognition through gaseous medium is also achieved.We further introduce application demonstrations of the developed film sensors to monitor exercise postures and physiological signals without direct contact between human body and the sensor,displaying great potential to be incorporated into future smart electronics.This study commendably expands the application scope of piezoelectret materials,which will have profound implications for exploring novel intelligent human–machine interactions.
基金supported in part by the Spectral Combs from UV to THz(SCOUT)and SIGMA+programs from the Defense Advanced Research Project Agency(DARPA)support from the Gordon and Betty Moore Foundation through Grant GBMF11446 to the University of Texas at Austin.
文摘Dispersion engineering is critical for the creation of integrated broadband laser frequency combs.In the long wavelength infrared range(LWIR,8-13µm),frequency combs based on quantum cascade lasers are attractive since they are monolithic,fundamental oscillators with high power levels and efficiencies.One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies,as this leads to flatter broadband gain spectra.However,as the gain bandwidth is increased,dispersion becomes the main limiting factor for comb bandwidth.Therefore,achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths.Here,we demonstrate the ultimate nanophotonic dispersion compensation scheme:an air-dielectric slab double-chirped mirror,which we fully integrate with the quantum cascade laser gain section.This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth.With this approach,we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations.Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.
