Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics mo...Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics model of the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body is amended.The research indicates that the change trends of zero lift drag coefficient and lift coefficient to Mach number are similar.The calculation result and wind tunnel experiment data all verify the validity of the amended dynamics model by which to estimate the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body,and thus providing some technical reference to aerodynamics character analysis of the same types of winged rigid body.展开更多
Rare-earth calcium oxyborate crystals(RECa_(4)O(BO_(3))_(3),RECOB,RE:rare-earth elements)are a kind of multifunctional crystal materials.In this work,the temperature dependent behaviors of the electroelastic constants...Rare-earth calcium oxyborate crystals(RECa_(4)O(BO_(3))_(3),RECOB,RE:rare-earth elements)are a kind of multifunctional crystal materials.In this work,the temperature dependent behaviors of the electroelastic constants of NdCOB crystal were investigated over the temperature range of-80-200℃,and their temperature coefficients were evaluated.It is found that NdCOB crystal possesses minimal variation of relative dielectric permittivities(<3%).The temperature coefficient of frequency for ZY cut with width shear vibration mode is in the order of 0.07×10^(-4)/℃.The temperature coefficients of the elastic compliances are obtained to be in the range of-33.0×10^(-4)/℃-32.2×10^(-4)/℃.Particularly,the sand swere found to show low temperature coefficients of the elastic compliances,i.e.1.0×10^(-4)/℃and-0.4×10^(-4)/℃,respectively,indicating the existence of zero temperature coefficient of frequency crystal cut.Furthermore,the electromechanical coupling factors and piezoelectric coefficients as a function of temperature were studied.The electromechanical coupling factor kand piezoelectric coefficient dare determined to be~30.8%and~15.2 pC/N at room temperature,respectively.The large piezoelectric response and zero temperature coefficient of frequency indicate the potential usage of NdCOB crystal for piezoelectric frequency devices over a wide temperature range.展开更多
文摘Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics model of the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body is amended.The research indicates that the change trends of zero lift drag coefficient and lift coefficient to Mach number are similar.The calculation result and wind tunnel experiment data all verify the validity of the amended dynamics model by which to estimate the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body,and thus providing some technical reference to aerodynamics character analysis of the same types of winged rigid body.
基金Project supported by the National Natural Science Foundation of China(51872165)the Primary Research&Development Plan of Shandong Province(2019JZZY010313)+1 种基金Shandong Provincial Natural Science Foundation(ZR2020KA003)the Shandong Province Innovative Talents Support Program(62350070311104)。
文摘Rare-earth calcium oxyborate crystals(RECa_(4)O(BO_(3))_(3),RECOB,RE:rare-earth elements)are a kind of multifunctional crystal materials.In this work,the temperature dependent behaviors of the electroelastic constants of NdCOB crystal were investigated over the temperature range of-80-200℃,and their temperature coefficients were evaluated.It is found that NdCOB crystal possesses minimal variation of relative dielectric permittivities(<3%).The temperature coefficient of frequency for ZY cut with width shear vibration mode is in the order of 0.07×10^(-4)/℃.The temperature coefficients of the elastic compliances are obtained to be in the range of-33.0×10^(-4)/℃-32.2×10^(-4)/℃.Particularly,the sand swere found to show low temperature coefficients of the elastic compliances,i.e.1.0×10^(-4)/℃and-0.4×10^(-4)/℃,respectively,indicating the existence of zero temperature coefficient of frequency crystal cut.Furthermore,the electromechanical coupling factors and piezoelectric coefficients as a function of temperature were studied.The electromechanical coupling factor kand piezoelectric coefficient dare determined to be~30.8%and~15.2 pC/N at room temperature,respectively.The large piezoelectric response and zero temperature coefficient of frequency indicate the potential usage of NdCOB crystal for piezoelectric frequency devices over a wide temperature range.
