Langasite (LGS) is a novel piezoelectric crystal. The authors numerically analyses the temperature stability of surface acoustic waves (SAW) and the relation of SAW propagation with temperature on certain optimal cuts...Langasite (LGS) is a novel piezoelectric crystal. The authors numerically analyses the temperature stability of surface acoustic waves (SAW) and the relation of SAW propagation with temperature on certain optimal cuts on LGS in this paper. The results show that LGS has better temperature stability than traditional piezo crystals. The results also demonstrate that the velocity of SAW decrease with temperature, the electro-mechanical coupling constant (k2) and temperature coefficient of frequency increases parabolically and the power flow angle increases linearly on certain optimal cuts of LGS. The calculation result compared with the experimental and show good agreement.展开更多
Langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary g...Langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary growth defects and they show strong X-ray kinematical contrast in the topographs. Another typical defect in LGS crystal is dislocation. The formation mechanisms of these growth defects in LGS crystals were discussed.展开更多
Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.Ho...Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.However,the accuracy of such sensors is often compromised by crosstalk between temperature and vibration signals.This study introduces a high-temperature vibration sensor based on langasite(LGS)surface acoustic wave(SAW)technology,designed to withstand temperatures up to 500℃.The sensor demonstrates high sensitivity,ranging from 12.54 kHz/g at 25℃ to 15.63 k Hz/g at 500℃.A comprehensive mechanical and electrical coupling model for the SAW vibration sensor was developed by integrating theoretical equations with numerical simulations to optimize the sensor's performance.Additionally,a novel decoupling algorithm for temperature and vibration was established,achieving thermomechanical decoupling with precise vibration parameters.Experimental results indicated a maximum relative deviation of 4.67%for the algorithm.In conclusion,the proposed LGS SAW vibration sensor emerges as a promising solution for the accurate detection of multiple parameters in high-temperature vibration monitoring.展开更多
Based on the analyses on amplitudes of historical variation of temperature and precipitation in the past 500 years and latest 100 years,according to the regional climate change scenarios for China estimated by composi...Based on the analyses on amplitudes of historical variation of temperature and precipitation in the past 500 years and latest 100 years,according to the regional climate change scenarios for China estimated by composite GCM,the potential impacts of climate change on cropping systems in China in future are simulated and assessed using the cropping system model development specially for the Chinese cropping patterns.It is shown that under the projected future climate change by 2050 the most parts of the present double cropping area would be replaced by the different triple cropping patterns while the current double cropping area would shift towards the central part of the present single cropping area.More explicitly,the northern boundary of triple cropping area would shift from its current border at the Changjing River to the Huanghe River,a shift of more than 5 degrees of latitude.And the shift of multiple cropping areas leads to a significant decrease of single cropping area. Furthermore,considering the changes mentioned above in combination with the likely negative balance of precipitation and evapotranspiration and,therefore,increase of moisture stress(i.e. less water availability),as well as the possible increase of heat stress disaster and decrease of LGS (length of growing season),the potential implication of climate change for agriculture in China are also analyzed roughly in this paper. As a result,however,it is still very difficult to reach a specific conclusion that the future climate change will he favorable or unfavorable to farm in China because of the complicated Chinese farming patterns,the complex-various social and economic environment of agricultural development and,especially,a great scientific uncertainties in the investigation/prediction of climate change.展开更多
文摘Langasite (LGS) is a novel piezoelectric crystal. The authors numerically analyses the temperature stability of surface acoustic waves (SAW) and the relation of SAW propagation with temperature on certain optimal cuts on LGS in this paper. The results show that LGS has better temperature stability than traditional piezo crystals. The results also demonstrate that the velocity of SAW decrease with temperature, the electro-mechanical coupling constant (k2) and temperature coefficient of frequency increases parabolically and the power flow angle increases linearly on certain optimal cuts of LGS. The calculation result compared with the experimental and show good agreement.
文摘Langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary growth defects and they show strong X-ray kinematical contrast in the topographs. Another typical defect in LGS crystal is dislocation. The formation mechanisms of these growth defects in LGS crystals were discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1837209 and 52105594)the Fundamental Research Program of Shanxi Province(Grant No.20210302124274)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2023L361)the Outstanding Young Talents Support Plan of Shanxi Provincethe Young Sanjin Scholar Distinguished Professor Plan of Shanxi Provincethe Innovative Research Group Project of the National Natural Science Foundation of China(Grant No.51821003)the Shanxi‘1331 Project’Key Subjects Construction。
文摘Monitoring high-temperature vibrations is critical in aerospace engineering,industrial manufacturing,and energy production,where harsh conditions necessitate robust vibration sensors for detecting anomalous signals.However,the accuracy of such sensors is often compromised by crosstalk between temperature and vibration signals.This study introduces a high-temperature vibration sensor based on langasite(LGS)surface acoustic wave(SAW)technology,designed to withstand temperatures up to 500℃.The sensor demonstrates high sensitivity,ranging from 12.54 kHz/g at 25℃ to 15.63 k Hz/g at 500℃.A comprehensive mechanical and electrical coupling model for the SAW vibration sensor was developed by integrating theoretical equations with numerical simulations to optimize the sensor's performance.Additionally,a novel decoupling algorithm for temperature and vibration was established,achieving thermomechanical decoupling with precise vibration parameters.Experimental results indicated a maximum relative deviation of 4.67%for the algorithm.In conclusion,the proposed LGS SAW vibration sensor emerges as a promising solution for the accurate detection of multiple parameters in high-temperature vibration monitoring.
文摘Based on the analyses on amplitudes of historical variation of temperature and precipitation in the past 500 years and latest 100 years,according to the regional climate change scenarios for China estimated by composite GCM,the potential impacts of climate change on cropping systems in China in future are simulated and assessed using the cropping system model development specially for the Chinese cropping patterns.It is shown that under the projected future climate change by 2050 the most parts of the present double cropping area would be replaced by the different triple cropping patterns while the current double cropping area would shift towards the central part of the present single cropping area.More explicitly,the northern boundary of triple cropping area would shift from its current border at the Changjing River to the Huanghe River,a shift of more than 5 degrees of latitude.And the shift of multiple cropping areas leads to a significant decrease of single cropping area. Furthermore,considering the changes mentioned above in combination with the likely negative balance of precipitation and evapotranspiration and,therefore,increase of moisture stress(i.e. less water availability),as well as the possible increase of heat stress disaster and decrease of LGS (length of growing season),the potential implication of climate change for agriculture in China are also analyzed roughly in this paper. As a result,however,it is still very difficult to reach a specific conclusion that the future climate change will he favorable or unfavorable to farm in China because of the complicated Chinese farming patterns,the complex-various social and economic environment of agricultural development and,especially,a great scientific uncertainties in the investigation/prediction of climate change.
