This study examined the temporal variation of the Normalized Difference Vegetation Index （NDVI） and its relationship with climatic factors in the Changbai Mountain Natural Reserve （CMNR） during 2000 - 2009. The re...This study examined the temporal variation of the Normalized Difference Vegetation Index （NDVI） and its relationship with climatic factors in the Changbai Mountain Natural Reserve （CMNR） during 2000 - 2009. The results showed as follows. The average NDVI values increased at a rate of 0.0024 year-1. The increase rate differed with vegetation types, such as 0.0034 year-1 for forest and 0.0017 year-1 for tundra. Trend analyses revealed a consistent NDVI increase at the start and end of the growing season but little variation or decrease observed in July during the study period. The NDVI in CMNR showed a stronger correlation with temperature than with precipitation, especially in spring and autumn. A stronger correlation was observed between NDVI and temperature in the tundra zone （2,000-2,600m） than in the coniferous forest （1,100-1,700m） and Korean pine-broadleaved mixed forest （7oo-1,1oom） zones. The results indicate that vegetation at higher elevations is more sensitive to temperature change. NDVI variation had a strong correlation with temperature change （r=0.7311, p〈0.01） but less significant correlation with precipitation change. The result indicates that temperature can serve as a main indicator of vegetation sensitivity in the CMNR.展开更多
A macroscopic frost heave model with more clear parameters was established. Based on a porosity rate frost heave model and segregation potential theory, a porosity rate function was deduced and introduced into the str...A macroscopic frost heave model with more clear parameters was established. Based on a porosity rate frost heave model and segregation potential theory, a porosity rate function was deduced and introduced into the stress-strain relationship. Numerical simulation was conducted and verified by frost heave tests. Results show that the porosity rate within the frozen fringe is proportional to the square of temperature gradient and current porosity, and is also proportional to the exponential function of applied pressure. The relative errors between the calculated and measured results of frost depth and frost heave are within 3% and 15% respectively, demonstrating that the temperature gradient, applied pressure and current porosity are the main influencing factors, while temperature is just the constraint of frozen fringe. The improved model have meaningful and accessible parameters, which can be used in engineering with good accuracy.展开更多
Effects of process and storage temperature on concentration of Maillard compounds in aseptic cold break tomato paste were evaluated during 12 months of storage time. Cold break tomato paste was processed at 104 ℃ or ...Effects of process and storage temperature on concentration of Maillard compounds in aseptic cold break tomato paste were evaluated during 12 months of storage time. Cold break tomato paste was processed at 104 ℃ or 112℃, aseptically filled into 5 liter bags, and stored at 21 ℃ and 33 ℃. Level of Browning Index, Furosine, and HMF was monitored in the aseptic cold break tomato paste during the storage time. Browning Index, Furosine, and HMF significantly increased in the aseptic cold break tomato paste during storage at 33℃, and there was linear correlation between Browning Index and Furosine （or HMF）. At the lower storage temperature of 21℃, no significant increases were observed. Effects of the process temperature on Browning Index, Furosine, and HMF of aseptic cold break tomato paste were less significant than the storage temperature.展开更多
This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous M...This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral （MBI） and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08：51：00-09：19：00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and Inn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with IRI ≥0.8 （R is the correlation coefficient between lnp and inn） and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method （αtrad=-0.15）. This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.展开更多
Superplastic alloy has very strong structure sensitivity. Superplastic bulging with a die of the plate is related not only to stress state but also closely to loading paths. It is an important basis for bulging formin...Superplastic alloy has very strong structure sensitivity. Superplastic bulging with a die of the plate is related not only to stress state but also closely to loading paths. It is an important basis for bulging forming with a die to study deformation law and experimental apparatus for superplastic free bulging, because the boundary of test piece is fixed and friction is insignificant for free bulging. In the paper, a pure high-pressure argon gas source is used as the loading media after it is heated by the heating system outside the furnace, which improves the heating efficiency and temperature uniformity of the test piece. The photoelectric non-contact measurement device can avoid negative influence on the additional stress and uneven temperature at the peak of bulging part caused by push rod in the contact measurement. The temperature and pressure of the test piece in cylindrical insulation furnace with blank holder give feedback control to improve the control precision. In loading gas channels, the pressure is adjusted by accurately measuring and controlling the rotation angle of the stepping motor, and is loaded by an electro-magnetic valve. It significantly increases the response characteristics of the control pressure. This paper also introduces steps and methods to realize several typical loading paths, such as constant pressure, jump pressure and additional back & differential pressure loading. These provide a new way to measure the strain rate sensitivity index m value and improve the deformation speed of superplastic free bulging.展开更多
基金supported by the Science and Technology Innovation Platforms Initiative of Northeast Normal University under the project "Ecological Security and Data Assemblage of the Changbai Mountains International Georegion(Project No.106111065202)"the National Grand Fundamental Research 973 Program of China (Project No.2009CB426305)
文摘This study examined the temporal variation of the Normalized Difference Vegetation Index （NDVI） and its relationship with climatic factors in the Changbai Mountain Natural Reserve （CMNR） during 2000 - 2009. The results showed as follows. The average NDVI values increased at a rate of 0.0024 year-1. The increase rate differed with vegetation types, such as 0.0034 year-1 for forest and 0.0017 year-1 for tundra. Trend analyses revealed a consistent NDVI increase at the start and end of the growing season but little variation or decrease observed in July during the study period. The NDVI in CMNR showed a stronger correlation with temperature than with precipitation, especially in spring and autumn. A stronger correlation was observed between NDVI and temperature in the tundra zone （2,000-2,600m） than in the coniferous forest （1,100-1,700m） and Korean pine-broadleaved mixed forest （7oo-1,1oom） zones. The results indicate that vegetation at higher elevations is more sensitive to temperature change. NDVI variation had a strong correlation with temperature change （r=0.7311, p〈0.01） but less significant correlation with precipitation change. The result indicates that temperature can serve as a main indicator of vegetation sensitivity in the CMNR.
基金Supported by National Natural Science Foundation of China (No. 40571032)Open Research Fund Program of State Key Laboratory for Geomechanics and Deep Underground Engineering (SKLGDUE 08001X)
文摘A macroscopic frost heave model with more clear parameters was established. Based on a porosity rate frost heave model and segregation potential theory, a porosity rate function was deduced and introduced into the stress-strain relationship. Numerical simulation was conducted and verified by frost heave tests. Results show that the porosity rate within the frozen fringe is proportional to the square of temperature gradient and current porosity, and is also proportional to the exponential function of applied pressure. The relative errors between the calculated and measured results of frost depth and frost heave are within 3% and 15% respectively, demonstrating that the temperature gradient, applied pressure and current porosity are the main influencing factors, while temperature is just the constraint of frozen fringe. The improved model have meaningful and accessible parameters, which can be used in engineering with good accuracy.
文摘Effects of process and storage temperature on concentration of Maillard compounds in aseptic cold break tomato paste were evaluated during 12 months of storage time. Cold break tomato paste was processed at 104 ℃ or 112℃, aseptically filled into 5 liter bags, and stored at 21 ℃ and 33 ℃. Level of Browning Index, Furosine, and HMF was monitored in the aseptic cold break tomato paste during the storage time. Browning Index, Furosine, and HMF significantly increased in the aseptic cold break tomato paste during storage at 33℃, and there was linear correlation between Browning Index and Furosine （or HMF）. At the lower storage temperature of 21℃, no significant increases were observed. Effects of the process temperature on Browning Index, Furosine, and HMF of aseptic cold break tomato paste were less significant than the storage temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.41431071,41174141,41474124)the National Basic Research Program of China(Grant No.2011CB811404)
文摘This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral （MBI） and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08：51：00-09：19：00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and Inn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with IRI ≥0.8 （R is the correlation coefficient between lnp and inn） and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method （αtrad=-0.15）. This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.
基金supported by the Natural Science Foundation of Jilin Province (Grant No. 201115015)the National Natural Science Foundation of China (Grant No. 51005099)
文摘Superplastic alloy has very strong structure sensitivity. Superplastic bulging with a die of the plate is related not only to stress state but also closely to loading paths. It is an important basis for bulging forming with a die to study deformation law and experimental apparatus for superplastic free bulging, because the boundary of test piece is fixed and friction is insignificant for free bulging. In the paper, a pure high-pressure argon gas source is used as the loading media after it is heated by the heating system outside the furnace, which improves the heating efficiency and temperature uniformity of the test piece. The photoelectric non-contact measurement device can avoid negative influence on the additional stress and uneven temperature at the peak of bulging part caused by push rod in the contact measurement. The temperature and pressure of the test piece in cylindrical insulation furnace with blank holder give feedback control to improve the control precision. In loading gas channels, the pressure is adjusted by accurately measuring and controlling the rotation angle of the stepping motor, and is loaded by an electro-magnetic valve. It significantly increases the response characteristics of the control pressure. This paper also introduces steps and methods to realize several typical loading paths, such as constant pressure, jump pressure and additional back & differential pressure loading. These provide a new way to measure the strain rate sensitivity index m value and improve the deformation speed of superplastic free bulging.
