The operational principle and the lumped parameters model of capacitive micro-accelerometer are introduced. The equivalent stiffness of different directions of the accelerometer is given. From the point of view of ene...The operational principle and the lumped parameters model of capacitive micro-accelerometer are introduced. The equivalent stiffness of different directions of the accelerometer is given. From the point of view of energy and mechanics, expressions of some key parameters, such as the damping, sensitivity, resolution of the accelerometer, are derived. The accelerometer noise behavior of mechanical-thermal noise in the open-loop system, along with the dynamic range of the open-loop system and closed-loop system is analyzed. The result is that the noise of the capacitive micro accelerometer is dominated by the magnitude of mechanical-thermal noise. At the same time, the magnitude of mechanical-thermal noise depends on the temperature and magnitude of mechanical damp. The result of the measurement from the implemented closed-loop microo-accelerometer system shows that the resolution is the level of rag, and the measurement range is from -50g to 50g.展开更多
Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme pr...Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.展开更多
There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects...There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.展开更多
This paper presents the characteristic thermal and chemical properties of some surface soil samples from the oil-producing regions of Nigeria. A microprocessor-based thermal analyzer was used to determine the thermal ...This paper presents the characteristic thermal and chemical properties of some surface soil samples from the oil-producing regions of Nigeria. A microprocessor-based thermal analyzer was used to determine the thermal conductivity while spectrophotometric procedure was employed to conduct the heavy metal concentration analysis. Thermal conductivity values were compared with heavy metal concentrations in each soil sample. The values of lead and cadmium and their respective measured thermal conductivities were highly correlated, with their correlation coefficients both greater than 0.900, while other metals showed no correlation.展开更多
The standard deviation of the central Pacific sea surface temperature anomaly （SSTA） during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the...The standard deviation of the central Pacific sea surface temperature anomaly （SSTA） during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the Central Pacific E1 Nifio （CP-E1 Nifio） and has a connection with the subtropical air-sea interaction in the northeastern Pacific. After removing the influence of the Eastern Pacific E1 Nifio, an S-EOF analysis is conducted and the leading mode shows a clear seasonal SSTA evolving from the subtropical northeastern Pacific to the tropical central Pacific with a quasi-biennial period. The initial subtropical SSTA is generated by the wind speed decrease and surface heat flux increase due to a north Pacific anomalous cyclone. Such subtropical SSTA can further influence the establishment of the SSTA in the tropical central Pacific via the wind-evaporation-SST （WES） feedback. After established, the central equatorial Pacific SSTA can be strengthened by the zonal advective feedback and thermocline feedback, and develop into CP-E1 Nifio. However, as the thermocline feedback increases the SSTA cooling after the mature phase, the heat flux loss and the reversed zonal advective feedback can cause the phase transition of CP-EI Nifio. Along with the wind stress variability, the recharge （discharge） process occurs in the central （eastern） equatorial Pacific and such a process causes the phase consistency between the thermocline depth and SST anomalies, which presents a contrast to the original recharge/discharge theory.展开更多
The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant...The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.展开更多
The stress strain curves of two CuZnAl shape memory alloys which have the martensitic transformation temperatures of 50 ℃ and -10 ℃ respectively, were measured by using electronic material tester after treated by di...The stress strain curves of two CuZnAl shape memory alloys which have the martensitic transformation temperatures of 50 ℃ and -10 ℃ respectively, were measured by using electronic material tester after treated by different heat-treatment conditions. The results show that the area enclosed by hysteresis loop of the CuZnAl shape memory alloy in martensitic state is much larger than that of the alloy in austenitic state with super-elasticity at room temperature. Therefore, the former has better vibration attenuation effect. After being oil-quenched, water-quenched, and step-quenched, the CuZnAl alloy takes on more stable shape memory effect,better super-plasticity and superelasticity (pseudoelasticity). A CuZnAl shape memory alloy damper was designed, produced and installed to a 2-layer frame structure. In addition, the vibration experiments were made by dynamic data collecting analysis meter. The velocity of vibration attenuation of frame structure with CuZnAl shape memory alloy damper is much faster than that without it. And with the help of CuZnAl shape memory alloy damper, the attenuation period reduces to 1/10 of the original.展开更多
This paper focuses on the temperature and pressure characteristics of a Swift-Backhaus type traveling-wave thermoacoustic prime mover during its onset and damping processes,in order to understand the intrinsic mechani...This paper focuses on the temperature and pressure characteristics of a Swift-Backhaus type traveling-wave thermoacoustic prime mover during its onset and damping processes,in order to understand the intrinsic mechanism of thermoacoustic oscillation onset and the feasibility of using low-grade thermal energy based on a low onset temperature. The influences of heat input and filling pressure on hysteretic loop,due to the noncoincidence between onset and damping processes,are measured and analyzed. The condition for the occurrence of hysteresis is also briefly discussed.展开更多
Aluminum production by carbothermo-chlorination reduction of alumina in vacuum was investigated by XRD, SEM, EDS and thermodynamic analysis. Thermodynamic calculations indicate that AlCl（g） generated by carbothermo-...Aluminum production by carbothermo-chlorination reduction of alumina in vacuum was investigated by XRD, SEM, EDS and thermodynamic analysis. Thermodynamic calculations indicate that AlCl（g） generated by carbothermo-chlorination process among Al2O3-C-AlCl3 system should be at 1377-1 900K （100 Pa） and AlCl（g） will disproportionate into aluminum and AlCl3（g） below 950-1 050 K at 10-102 Pa. Experimental results demonstrate that Al4O4C and Al4C3 begin to be formed by Al2O3-C system over 1698 K （40-150Pa）. It is Al4O4C and Al4C3 but not Al2O3-C that participate in the carbothermic-chlorination reaction. Temperature for AlCl（g） generated by Al4O4C-AlCl3-C, Al4C3-Al2O3-AlCl3 and Al4OC-Al4C3-Al2O3-AlCl3-C system is 1 703-1853 K （40-150 Pa）. Aluminum metal is produced by AlCl（g） disproportionation process below 933 K. The average purity of aluminum metal reaches 95.32%, which has perfect crystallization and uniform grain size.展开更多
文摘The operational principle and the lumped parameters model of capacitive micro-accelerometer are introduced. The equivalent stiffness of different directions of the accelerometer is given. From the point of view of energy and mechanics, expressions of some key parameters, such as the damping, sensitivity, resolution of the accelerometer, are derived. The accelerometer noise behavior of mechanical-thermal noise in the open-loop system, along with the dynamic range of the open-loop system and closed-loop system is analyzed. The result is that the noise of the capacitive micro accelerometer is dominated by the magnitude of mechanical-thermal noise. At the same time, the magnitude of mechanical-thermal noise depends on the temperature and magnitude of mechanical damp. The result of the measurement from the implemented closed-loop microo-accelerometer system shows that the resolution is the level of rag, and the measurement range is from -50g to 50g.
基金supported by the program under Grant No.2007BAC29B04
文摘Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.
基金funded by the National Natural Science Foundation of China[grant number 41776031]the Guangdong Natural Science Foundation[grant number 2015A030313796]+3 种基金the National Program on Global Change and Air-Sea Interaction[grant number GASI-IPOVAI-04]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010104]the program for scientific research start-upfunds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
文摘There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.
文摘This paper presents the characteristic thermal and chemical properties of some surface soil samples from the oil-producing regions of Nigeria. A microprocessor-based thermal analyzer was used to determine the thermal conductivity while spectrophotometric procedure was employed to conduct the heavy metal concentration analysis. Thermal conductivity values were compared with heavy metal concentrations in each soil sample. The values of lead and cadmium and their respective measured thermal conductivities were highly correlated, with their correlation coefficients both greater than 0.900, while other metals showed no correlation.
基金supported by the National Basic Research Program of China(973Program:2012CB955604)National Natural Science Foundation of China(Nos.40975038and40830106)+5 种基金the CMA Program(GYHY200906008)the financial support provided by the China Scholarship Counciljointly supported by the 973 Program of China(2010CB950404)DOE grant DE-SC0005110National Science Foundation(NSF)grants ATM1034798NOAA grand NA10OAR4310200
文摘The standard deviation of the central Pacific sea surface temperature anomaly （SSTA） during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the Central Pacific E1 Nifio （CP-E1 Nifio） and has a connection with the subtropical air-sea interaction in the northeastern Pacific. After removing the influence of the Eastern Pacific E1 Nifio, an S-EOF analysis is conducted and the leading mode shows a clear seasonal SSTA evolving from the subtropical northeastern Pacific to the tropical central Pacific with a quasi-biennial period. The initial subtropical SSTA is generated by the wind speed decrease and surface heat flux increase due to a north Pacific anomalous cyclone. Such subtropical SSTA can further influence the establishment of the SSTA in the tropical central Pacific via the wind-evaporation-SST （WES） feedback. After established, the central equatorial Pacific SSTA can be strengthened by the zonal advective feedback and thermocline feedback, and develop into CP-E1 Nifio. However, as the thermocline feedback increases the SSTA cooling after the mature phase, the heat flux loss and the reversed zonal advective feedback can cause the phase transition of CP-EI Nifio. Along with the wind stress variability, the recharge （discharge） process occurs in the central （eastern） equatorial Pacific and such a process causes the phase consistency between the thermocline depth and SST anomalies, which presents a contrast to the original recharge/discharge theory.
基金supported by the National Key Research and Development Program of China [grant number2018YFC1506903]the National Natural Science Foundation of China [grant number 41776031]+2 种基金the Guangdong Natural Science Foundation [grant number 2015A030313796]the program for scientific research start-up funds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
文摘The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.
文摘The stress strain curves of two CuZnAl shape memory alloys which have the martensitic transformation temperatures of 50 ℃ and -10 ℃ respectively, were measured by using electronic material tester after treated by different heat-treatment conditions. The results show that the area enclosed by hysteresis loop of the CuZnAl shape memory alloy in martensitic state is much larger than that of the alloy in austenitic state with super-elasticity at room temperature. Therefore, the former has better vibration attenuation effect. After being oil-quenched, water-quenched, and step-quenched, the CuZnAl alloy takes on more stable shape memory effect,better super-plasticity and superelasticity (pseudoelasticity). A CuZnAl shape memory alloy damper was designed, produced and installed to a 2-layer frame structure. In addition, the vibration experiments were made by dynamic data collecting analysis meter. The velocity of vibration attenuation of frame structure with CuZnAl shape memory alloy damper is much faster than that without it. And with the help of CuZnAl shape memory alloy damper, the attenuation period reduces to 1/10 of the original.
基金the National Natural Science Foundation of China (Nos. 50776075 and 50536040)the Natural ScienceFoundation of Zhejiang Province (No. Y107229), China
文摘This paper focuses on the temperature and pressure characteristics of a Swift-Backhaus type traveling-wave thermoacoustic prime mover during its onset and damping processes,in order to understand the intrinsic mechanism of thermoacoustic oscillation onset and the feasibility of using low-grade thermal energy based on a low onset temperature. The influences of heat input and filling pressure on hysteretic loop,due to the noncoincidence between onset and damping processes,are measured and analyzed. The condition for the occurrence of hysteresis is also briefly discussed.
基金Project(u0837604) supported by the Joint Funds of the National Natural Science Foundation of China and Yunnan ProvinceProject(20095314110003) supported by the special Research Funds of the Docter Subject of Higher School,China
文摘Aluminum production by carbothermo-chlorination reduction of alumina in vacuum was investigated by XRD, SEM, EDS and thermodynamic analysis. Thermodynamic calculations indicate that AlCl（g） generated by carbothermo-chlorination process among Al2O3-C-AlCl3 system should be at 1377-1 900K （100 Pa） and AlCl（g） will disproportionate into aluminum and AlCl3（g） below 950-1 050 K at 10-102 Pa. Experimental results demonstrate that Al4O4C and Al4C3 begin to be formed by Al2O3-C system over 1698 K （40-150Pa）. It is Al4O4C and Al4C3 but not Al2O3-C that participate in the carbothermic-chlorination reaction. Temperature for AlCl（g） generated by Al4O4C-AlCl3-C, Al4C3-Al2O3-AlCl3 and Al4OC-Al4C3-Al2O3-AlCl3-C system is 1 703-1853 K （40-150 Pa）. Aluminum metal is produced by AlCl（g） disproportionation process below 933 K. The average purity of aluminum metal reaches 95.32%, which has perfect crystallization and uniform grain size.
