The standard Gibbs energies of transfer (Δ tr G 0) for potassium tetraphenylborate (KBPh 4) have been studied in the systems of water and water +1 propanol (PrOH) as well as water and water + t butyl alcohol (TBA) at...The standard Gibbs energies of transfer (Δ tr G 0) for potassium tetraphenylborate (KBPh 4) have been studied in the systems of water and water +1 propanol (PrOH) as well as water and water + t butyl alcohol (TBA) at 298.15?K. The results show that -Δ tr G 0 exhibits a complicated changing pattern with the mole fraction of TBA( x (TBA)) or PrOH ( x (PrOH)), and Δ tr G 0 has the a maximum value at x (TBA) = 0.2 or x (PrOH)=0.2. Especially, -Δ tr G 0 of KBPh 4 changes unusually with increasing x (TBA) when x (TBA) < 0.05. The reasons for these changes were analyzed and discussed.展开更多
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision. It is important f...Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision. It is important for certification institutions to explore methods for updating and transferring present standards, to accelerate the transfer of standard information and ensure present standards are implemented in a timely manner.展开更多
This paper presents the results of a stability study of a photodiode realized in the Laboratoire de Métrologie des Rayonnements (LMR-INSAT, Tunisia). The study was performed during six years and concerned with th...This paper presents the results of a stability study of a photodiode realized in the Laboratoire de Métrologie des Rayonnements (LMR-INSAT, Tunisia). The study was performed during six years and concerned with the photodiode optical and electrical characteristics. This study involves in one side, the reflectivity stability for different wavelengths and in the other side, the stability of the series and shunt resistances. The experimental results confirm the stability of the photodiode spectral response since the reflection coefficient maximum uncertainty is equal to 0.0055 with an experimental uncertainty of about 0.0016 (at 1? level) for the mean value of the reflectivity over the study duration. Moreover, the shunt and series resistances are equal to 5.14 k? and 7.61 ? respectively with an uncertainty value of 0.01 k? and 0.04 ? respectively (at 1? level). This photodiode does not display any ageing aspect. Consequently, the PSiZ photodiode can be used as a Transfer Standard for radiometric measurement in the visible spectral range.展开更多
Regional drought analysis provides useful information for sustainable water resources management.In this paper,a standardized precipitation index(SPI) at multiple time scales was used to investigate the spatial patter...Regional drought analysis provides useful information for sustainable water resources management.In this paper,a standardized precipitation index(SPI) at multiple time scales was used to investigate the spatial patterns and trends of drought in the Han River Basin,one of the largest tributaries of Yangtze River,China.It was found that,in terms of drought severity,the upper basin of the Han River is the least,while the growing trend is the most conspicuous;a less conspicuous growing trend can be observed in the middle basin;and there is an insignificant decreasing trend in the lower basin.Meanwhile,the impact of drought on the Middle Route of the South-to-North Water Transfer Project was investigated,and it is suggested that water intake must be reduced in times of drought,particularly when successive or simultaneous droughts in the upper and middle basins of the Han River Basin occur.The results can provide substantial information for future water allocation schemes of the South-to-North Water Transfer Project.展开更多
文摘The standard Gibbs energies of transfer (Δ tr G 0) for potassium tetraphenylborate (KBPh 4) have been studied in the systems of water and water +1 propanol (PrOH) as well as water and water + t butyl alcohol (TBA) at 298.15?K. The results show that -Δ tr G 0 exhibits a complicated changing pattern with the mole fraction of TBA( x (TBA)) or PrOH ( x (PrOH)), and Δ tr G 0 has the a maximum value at x (TBA) = 0.2 or x (PrOH)=0.2. Especially, -Δ tr G 0 of KBPh 4 changes unusually with increasing x (TBA) when x (TBA) < 0.05. The reasons for these changes were analyzed and discussed.
文摘Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision. It is important for certification institutions to explore methods for updating and transferring present standards, to accelerate the transfer of standard information and ensure present standards are implemented in a timely manner.
文摘This paper presents the results of a stability study of a photodiode realized in the Laboratoire de Métrologie des Rayonnements (LMR-INSAT, Tunisia). The study was performed during six years and concerned with the photodiode optical and electrical characteristics. This study involves in one side, the reflectivity stability for different wavelengths and in the other side, the stability of the series and shunt resistances. The experimental results confirm the stability of the photodiode spectral response since the reflection coefficient maximum uncertainty is equal to 0.0055 with an experimental uncertainty of about 0.0016 (at 1? level) for the mean value of the reflectivity over the study duration. Moreover, the shunt and series resistances are equal to 5.14 k? and 7.61 ? respectively with an uncertainty value of 0.01 k? and 0.04 ? respectively (at 1? level). This photodiode does not display any ageing aspect. Consequently, the PSiZ photodiode can be used as a Transfer Standard for radiometric measurement in the visible spectral range.
基金Project supported by the National Natural Science Foundation of China (No.50809058)the International Science and Technology Cooperation Program of China (No.2010DFA24320)
文摘Regional drought analysis provides useful information for sustainable water resources management.In this paper,a standardized precipitation index(SPI) at multiple time scales was used to investigate the spatial patterns and trends of drought in the Han River Basin,one of the largest tributaries of Yangtze River,China.It was found that,in terms of drought severity,the upper basin of the Han River is the least,while the growing trend is the most conspicuous;a less conspicuous growing trend can be observed in the middle basin;and there is an insignificant decreasing trend in the lower basin.Meanwhile,the impact of drought on the Middle Route of the South-to-North Water Transfer Project was investigated,and it is suggested that water intake must be reduced in times of drought,particularly when successive or simultaneous droughts in the upper and middle basins of the Han River Basin occur.The results can provide substantial information for future water allocation schemes of the South-to-North Water Transfer Project.
