Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly...Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly implanting small NiFe204 clusters on reduced graphene oxide is demonstrated, wherein the magnetic clusters are tailored, and more significantly, the electromagnetic properties are highly tuned. The microwave absorption was efficiently optimized yielding a maximum reflection loss of -58 dB and - 12 times broadening of the bandwidth （at -10 dB）. Furthermore, tailoring of the implanted magnetic clusters successfully realized the selective-frequency microwave absorption, and the absorption peak could shift from 4.6 to 16 GHz covering 72% of the measured frequency range. The fascinating performances eventuate from the appropriately tailored clusters, which provide optimal synergistic effects of the dielectric and magnetic loss caused by multi-relaxation, conductance, and resonances. These findings open new avenues for designing microwave absorption materials in future, and the well-tailored NiFe204-rGO can be readily applied as a multi-functional microwave absorption material in various fields ranging from civil and commerce to military and aerospace.展开更多
Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si...Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si/Al ratio (Si/Al=4.6-6.1), high surface area (1090 m2/g) and the average diameter of nanosized NaY (75 nm) synthesized is 30 nm, it is smaller than that of without starch additive.展开更多
An outbreak of COVID-19 developed aboard the Princess Cruises Ship during January eFebruary 2020.Using mathematical modeling and time-series incidence data describing the trajectory of the outbreak among passengers an...An outbreak of COVID-19 developed aboard the Princess Cruises Ship during January eFebruary 2020.Using mathematical modeling and time-series incidence data describing the trajectory of the outbreak among passengers and crew members,we characterize how the transmission potential varied over the course of the outbreak.Our estimate of the mean reproduction number in the confined setting reached values as high as^11,which is higher than mean estimates reported from community-level transmission dynamics in China and Singapore(approximate range:1.1e7).Our findings suggest that Rt decreased substantially compared to values during the early phase after the Japanese government implemented an enhanced quarantine control.Most recent estimates of Rt reached values largely below the epidemic threshold,indicating that a secondary outbreak of the novel coronavirus was unlikely to occur aboard the Diamond Princess Ship.展开更多
The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that t...The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that the fracturing of surrounding rock in confined blasting condition is the result of coaction of rock pre-cracking by shock wave and stress wave and the continuing expanding crackenhancement of confined medium, and the model of crack development of borehole surrounding rock in confined blasting condition was established. This study acquired the damage range of surrounding rock under the action of shock wave and stress wave, as well as the crack development characteristics of surrounding rock after the wedge-in confined medium into the crack space. Deep-hole confined blasting experiment on large rock showed that the high-efficient utilisation of in-hole explosive was achieved and the safety of rock blasting operation was ensured. Safe static rock-breaking under the action of high-efficient explosive blasting was achieved as well as the unification of super dynamic load of explosive blasting and static rock-breaking of water medium.展开更多
Nowadays, the researches of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) tech- nique to monitor the land subsidence are mainly on how to qualitatively analyze the subsidence areas and values, ...Nowadays, the researches of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) tech- nique to monitor the land subsidence are mainly on how to qualitatively analyze the subsidence areas and values, but the analysis of subsidence process and mechanism are insufficient. In order to resolve these problems, 6 scenes of ERS1/2 images captured during 1995 and 2000 in a certain place of Jiangsu province were selected to obtain the subsidence and velocities in three time segments by ''two-pass'' D- InSAR method. Then the relationships among distributions of pumping wells, exploitation quantity of groundwater, and confined water levels were studied and the subsidence mechanism was systematically analyzed. The results show that using D-InSAR technique to monitor the deformation of large area can obtain high accuracies, the disadvantages of classical observation methods can be remedied and there is a linear relationship among the velocities of land subsidence, the water level and the exploitation quantity.展开更多
This paper examines the influence of gravity on the bulk responses of a granular solid. The loading scenarios in this study include confined compression, rod penetration into a granular medium and discharging through ...This paper examines the influence of gravity on the bulk responses of a granular solid. The loading scenarios in this study include confined compression, rod penetration into a granular medium and discharging through an orifice. Similar loading and flow conditions are likely to be encountered in the stress and deformation regimes that regoliths are subjected to in extraterrestrial exploration activities including in situ resource utilisation processes. Both spherical and non-spherical particles were studied using the discrete element method （DEM）. Whilst DEM is increasingly used to model granular solids, careful validations of the simulation outcomes are rather rare. Thus in addition to exploring the effect of gravity, this paper also compares DEM simulations with experiments under terrestrial condition to verify whether DEM can produce satisfactory predictions. The terrestrial experiments were conducted with great care and simulated closely using DEM. The key mechanical and geometrical properties for the particles were measured in laboratory tests for use in the DEM simulations. A series of DEM computations were then performed under reduced gravity to simulate these experiments under extraterrestrial environment. It was found that gravity has no noticeable effect on the force transmission in the confined compression case; the loading gradient in the rod penetration is linearly proportional to the gravity; the mass flow rate in silo discharge is proportional to square root of the gravity and the angle of repose increases with reducing gravity. These findings are in agreement with expectation and existing scientific evidence.展开更多
基金This work was supported by the National Natural Science Foundation of China （NSFC） （Nos. 11774027, 51132002, 51072024 and 51372282）.
文摘Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly implanting small NiFe204 clusters on reduced graphene oxide is demonstrated, wherein the magnetic clusters are tailored, and more significantly, the electromagnetic properties are highly tuned. The microwave absorption was efficiently optimized yielding a maximum reflection loss of -58 dB and - 12 times broadening of the bandwidth （at -10 dB）. Furthermore, tailoring of the implanted magnetic clusters successfully realized the selective-frequency microwave absorption, and the absorption peak could shift from 4.6 to 16 GHz covering 72% of the measured frequency range. The fascinating performances eventuate from the appropriately tailored clusters, which provide optimal synergistic effects of the dielectric and magnetic loss caused by multi-relaxation, conductance, and resonances. These findings open new avenues for designing microwave absorption materials in future, and the well-tailored NiFe204-rGO can be readily applied as a multi-functional microwave absorption material in various fields ranging from civil and commerce to military and aerospace.
文摘Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si/Al ratio (Si/Al=4.6-6.1), high surface area (1090 m2/g) and the average diameter of nanosized NaY (75 nm) synthesized is 30 nm, it is smaller than that of without starch additive.
文摘An outbreak of COVID-19 developed aboard the Princess Cruises Ship during January eFebruary 2020.Using mathematical modeling and time-series incidence data describing the trajectory of the outbreak among passengers and crew members,we characterize how the transmission potential varied over the course of the outbreak.Our estimate of the mean reproduction number in the confined setting reached values as high as^11,which is higher than mean estimates reported from community-level transmission dynamics in China and Singapore(approximate range:1.1e7).Our findings suggest that Rt decreased substantially compared to values during the early phase after the Japanese government implemented an enhanced quarantine control.Most recent estimates of Rt reached values largely below the epidemic threshold,indicating that a secondary outbreak of the novel coronavirus was unlikely to occur aboard the Diamond Princess Ship.
基金supported by the National Natural Science Foundation(Nos.51574220,51604262)the Foundation Research Project of Jiangsu Province(No.BK20160256)+1 种基金the Postdoctoral Science Foundation(No.2015M581896)the Postdoctoral Science Foundation Project of Jiangsu Province(No.1601212C)
文摘The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that the fracturing of surrounding rock in confined blasting condition is the result of coaction of rock pre-cracking by shock wave and stress wave and the continuing expanding crackenhancement of confined medium, and the model of crack development of borehole surrounding rock in confined blasting condition was established. This study acquired the damage range of surrounding rock under the action of shock wave and stress wave, as well as the crack development characteristics of surrounding rock after the wedge-in confined medium into the crack space. Deep-hole confined blasting experiment on large rock showed that the high-efficient utilisation of in-hole explosive was achieved and the safety of rock blasting operation was ensured. Safe static rock-breaking under the action of high-efficient explosive blasting was achieved as well as the unification of super dynamic load of explosive blasting and static rock-breaking of water medium.
基金provided by the National Natural Science Foundation of China (No.41071273)the Fundamental Research Funds for the Central Universities (No. 2010QNA21)the Project Sponsored by the Scientific Research Foundation of Key Laboratory for Land Environmentand Disaster Monitoring of SBSM (No. LEDM2011B07)
文摘Nowadays, the researches of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) tech- nique to monitor the land subsidence are mainly on how to qualitatively analyze the subsidence areas and values, but the analysis of subsidence process and mechanism are insufficient. In order to resolve these problems, 6 scenes of ERS1/2 images captured during 1995 and 2000 in a certain place of Jiangsu province were selected to obtain the subsidence and velocities in three time segments by ''two-pass'' D- InSAR method. Then the relationships among distributions of pumping wells, exploitation quantity of groundwater, and confined water levels were studied and the subsidence mechanism was systematically analyzed. The results show that using D-InSAR technique to monitor the deformation of large area can obtain high accuracies, the disadvantages of classical observation methods can be remedied and there is a linear relationship among the velocities of land subsidence, the water level and the exploitation quantity.
文摘This paper examines the influence of gravity on the bulk responses of a granular solid. The loading scenarios in this study include confined compression, rod penetration into a granular medium and discharging through an orifice. Similar loading and flow conditions are likely to be encountered in the stress and deformation regimes that regoliths are subjected to in extraterrestrial exploration activities including in situ resource utilisation processes. Both spherical and non-spherical particles were studied using the discrete element method （DEM）. Whilst DEM is increasingly used to model granular solids, careful validations of the simulation outcomes are rather rare. Thus in addition to exploring the effect of gravity, this paper also compares DEM simulations with experiments under terrestrial condition to verify whether DEM can produce satisfactory predictions. The terrestrial experiments were conducted with great care and simulated closely using DEM. The key mechanical and geometrical properties for the particles were measured in laboratory tests for use in the DEM simulations. A series of DEM computations were then performed under reduced gravity to simulate these experiments under extraterrestrial environment. It was found that gravity has no noticeable effect on the force transmission in the confined compression case; the loading gradient in the rod penetration is linearly proportional to the gravity; the mass flow rate in silo discharge is proportional to square root of the gravity and the angle of repose increases with reducing gravity. These findings are in agreement with expectation and existing scientific evidence.
