Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remain...Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remains elusive. We experimentally studied the thermal and strain rate- dependent viscoelastic behavior of skin in uniaxial stretch and numerically investigated the effects of temperature and strain rate on pain sensation. The results indicate that the viscosity of skin tissue decreases with increasing temperature and reducing strain rate, which subsequently decreases the discharge frequency of skin nociceptor and thus relieves the pain sensation. The results would contribute to the understanding of pain relief mechanism and optimizing for mechanical treatment.展开更多
The microstructural features of high-temperature sintered and CaO-MgO-Al_2O_3-SiO_2(CMAS) corroded air plasma sprayed Y_2O_3 stabilized ZrO_2(YSZ) thermal barrier coatings(TBCs) under the thermal gradient condition we...The microstructural features of high-temperature sintered and CaO-MgO-Al_2O_3-SiO_2(CMAS) corroded air plasma sprayed Y_2O_3 stabilized ZrO_2(YSZ) thermal barrier coatings(TBCs) under the thermal gradient condition were comparatively studied. As-sprayed YSZ has a lamellar structure and the lamellae are composed of closely aligned columnar crystals. The sintered and the CMAS corroded YSZ coatings maintain the t'-ZrO_2 phase as the as-sprayed YSZ coating. The sintered YSZ remains the lamellar structure with reduced interlamellar gaps and grains coarsening. After the CMAS corrosion, the top layer of the YSZ coating keeps its lamellar structure consisting of some columnar grains with the CMAS infiltration into the intergrain gaps and the formation of striped Zr_2Y_2 O_7. The typical lamellar structure transforms into more equiaxed grains in the middle and bottom layers of the ceramic coating along with significant infiltration of amorphous CMAS and anorthite formation in the bottom layer owing to the high contents of Ca and Al.展开更多
The optimum loading for rotors has previously been found for hover, climb and wind turbine conditions; but, up to now, no one has determined the optimum rotor loading in descent. This could be an important design cons...The optimum loading for rotors has previously been found for hover, climb and wind turbine conditions; but, up to now, no one has determined the optimum rotor loading in descent. This could be an important design consideration for rotary-wing parachutes and low-speed des- cents. In this paper, the optimal loading for a powered rotor in descent is found from momentum theory based on a variational principle. This loading is compared with the optimal loading for a rotor in hover or climb and with the Betz rotor loading （which is optimum for a lightly-loaded rotor）. Wake contraction for each of the various loadings is also presented.展开更多
基金supported by the National Natural Science Foundation of China (11372243, 11372243, 1152219)the International Science and Technology Cooperation Program of China (2013DFG02930)
文摘Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remains elusive. We experimentally studied the thermal and strain rate- dependent viscoelastic behavior of skin in uniaxial stretch and numerically investigated the effects of temperature and strain rate on pain sensation. The results indicate that the viscosity of skin tissue decreases with increasing temperature and reducing strain rate, which subsequently decreases the discharge frequency of skin nociceptor and thus relieves the pain sensation. The results would contribute to the understanding of pain relief mechanism and optimizing for mechanical treatment.
基金supported financially by the National Natural Science Foundation of China (Nos. 51590891 and 11772288)the opening project of State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology, the opening project No. KFJJ15-05M)"Hundred Talents Program" of Hunan Province, China
文摘The microstructural features of high-temperature sintered and CaO-MgO-Al_2O_3-SiO_2(CMAS) corroded air plasma sprayed Y_2O_3 stabilized ZrO_2(YSZ) thermal barrier coatings(TBCs) under the thermal gradient condition were comparatively studied. As-sprayed YSZ has a lamellar structure and the lamellae are composed of closely aligned columnar crystals. The sintered and the CMAS corroded YSZ coatings maintain the t'-ZrO_2 phase as the as-sprayed YSZ coating. The sintered YSZ remains the lamellar structure with reduced interlamellar gaps and grains coarsening. After the CMAS corrosion, the top layer of the YSZ coating keeps its lamellar structure consisting of some columnar grains with the CMAS infiltration into the intergrain gaps and the formation of striped Zr_2Y_2 O_7. The typical lamellar structure transforms into more equiaxed grains in the middle and bottom layers of the ceramic coating along with significant infiltration of amorphous CMAS and anorthite formation in the bottom layer owing to the high contents of Ca and Al.
基金sponsored by the GT/WU Rotorcraft Center of Excellence Program,Dr.Mahendra Bhagwat,technical monitor
文摘The optimum loading for rotors has previously been found for hover, climb and wind turbine conditions; but, up to now, no one has determined the optimum rotor loading in descent. This could be an important design consideration for rotary-wing parachutes and low-speed des- cents. In this paper, the optimal loading for a powered rotor in descent is found from momentum theory based on a variational principle. This loading is compared with the optimal loading for a rotor in hover or climb and with the Betz rotor loading （which is optimum for a lightly-loaded rotor）. Wake contraction for each of the various loadings is also presented.
