Spatial heterogeneity of dead fuel moisture content in a Larix gmelinii forest in Inner Mongolia using geostatistics

Spatial heterogeneity of fuel moisture content determines the spread rate and direction of a forest fire.Research on the spatial heterogeneity of the moisture content of dead fuel of Larix gmelinii Rupr.showed that:(1)fuel moisture content in litter layer<semi-humus layer<humus layer,and the coefficient of variation decreased with sampling depth;(2)the sill value of the semi-humus layer was highest,the humus layer moderate,the litter layer the smallest,overall,the spatial heterogeneity of the semi-humus layer was the highest.The humus layer in the slant direction and three layers in a vertical direction showed strong spatial correlation with the lowest nugget coefficient of 0.0968;(3)the fuel moisture content of the humus layer showed strong spatial anisotropy;and,(4)estimating the total moisture content of the sampling site by stimulated sampling reasonable control of the sampling interval,and increasing the sampling intensity can reduce the error.When the sampling intensity is increased to more than 16 and the sampling interval 3 m,the standard error is<15%.The spatial heterogeneity of fuel moisture content is best revealed by increasing sampling density,sampling in different fire seasons,and in different slope directions and positions.The results can provide a scientific basis for forest fire prediction and prevention.

Switchable near-infrared photoluminescence of PbS quantum dots through light and heat modulated hole transfer to spiropyran molecules

Precise modulation of photoluminescence(PL)of nanomaterials by external control is of great interest in such diverse areas as photocatalysis,memory and sensing.Recent studies have combined colloidal quantum dots(QDs)with photochromic molecules to construct optically switchable PL systems.However,it still remains challenging to switch the PL on and off in the near-infrared(NIR)region with multi-stimuli such as light and heat.Here,we present light and heat triggered modulation of the NIR PL of PbS QDs using adjacent spiropyran derivatives.The NIR PL of PbS was reversibly switched on and off through the isomerization process of spiropyran molecules that can be triggered by either light irradiation or heating.The PL intensity of the off state is low enough to yield an on/off ratio as high as 54.Transient absorption measurements revealed ultrafast photoinduced hole transfer from PbS to spiropyran,the rate and efficiency of which depend critically on the driving force that can be deeply modulated through spiropyran isomerization.This study not only establishes a novel multi-stimuli switchable PL system in the NIR,but also provides fundamental guidelines for the design for such systems for a variety of emerging applications.

Self-adaptive rolling motion for snake robots in unstructured environments based on torque control

Snake robots have great potential for exploring and operating in challenging unstructured environments,such as rubble,caves,and narrow pipelines.However,due to the complexity and unpredictability of unstructured environments,designing a controller that can achieve adaptive motion is crucial.This paper proposes a self-adaptive torque-based rolling controller for snake robots,enabling compliant motion in unstructured environments.First,a controller is designed to modify the torque of each motor by focusing on the different motion states of the rolling gait.Second,an experimental platform is established for snake robots to verify the effectiveness of the controller.Finally,a series of rolling experiments are conducted using the torque-based rolling controller.In conclusion,the self-adaptive torque-based rolling controller enhances snake robot adaptability and mobility.