本文在分析比较各种传统的维护数据库物理一致性的方法的基础上提出了一种既经济又实用的维护恢复策略,即延缓写盘的DLRU(Delay Least Recently Used)缓冲策略。这种方法改变了传统的LRU策略。LRU策略对于被排挤出缓冲区的块,若已改动,...本文在分析比较各种传统的维护数据库物理一致性的方法的基础上提出了一种既经济又实用的维护恢复策略,即延缓写盘的DLRU(Delay Least Recently Used)缓冲策略。这种方法改变了传统的LRU策略。LRU策略对于被排挤出缓冲区的块,若已改动,则立即将该块回写到盘上以便让出空间读进新块,而DLRU遇此情况,则将该快接到LRU链尾上(使它不被挤出的优先级最高),顺链继继找下去,直到找到未被改动过的块为止,在此过程中凡遇改过的块都依次接到链尾上,新读进的块就覆盖在所找到的未被改动的块上。如果整个缓冲区都已改动,则将缓冲区的所有块排序后一次性回写到外存上。如果系统在回写前发生了故障(各种故障),则用户键入一“作废”命令就将缓冲区中的全部块废除;如果用户在一系列的更新(增删改)操作后未发生异常,则键入“生效”命令,系统接到此命令后立即将缓冲区中所有块排序后写盘。当发生前述的缓冲区所有块都改过(且此时缓冲区已满)而用户至此未发生“生效”或“作废”命令,则系统暂停运行,强迫用户在“生效”和“作废”中必选一操作。为防止在回写过程中发生故障,此法要与其他方法配合使用。展开更多
After four years of effort,the Beijing Institute of Control Engineering completed the development of the thirdgeneration camera type rendezvous and docking sensor(CRDS)for imaging and measurement of the spaceship and ...After four years of effort,the Beijing Institute of Control Engineering completed the development of the thirdgeneration camera type rendezvous and docking sensor(CRDS)for imaging and measurement of the spaceship and the target spacecraft at short range during rendezvous and docking.CRDS consists of a camera onboard the spaceship and a target designator onboard the target spacecraft.The relative展开更多
A novel system for measuring net photochemical ozone production rates in the atmosphere based on cavity ring-down spectroscopy(OPR-CRDS)was developed.The system consists of two chambers(a reaction chamber and a refere...A novel system for measuring net photochemical ozone production rates in the atmosphere based on cavity ring-down spectroscopy(OPR-CRDS)was developed.The system consists of two chambers(a reaction chamber and a reference chamber)and a dual-channel O_(x)-CRDS detector.To minimize the wall loss of O_(x)in the chambers,the inner surfaces of both chambers are coated with Teflon film.The performance of the OPR-CRDS system was characterized.It was found that even though the photolysis frequency(J value)decreased by 10%,the decrease in the P(O_(3))caused by the ultraviolet-blocking film coating was less than 3%.The two chambers had a good consistency in the mean residence time and the measurement of NO_(2)and O_(x)under the condition of no sunlight.The detection limit of the OPR-CRDS was determined to be 0.20 ppbv/hr.To further verify the accuracy of the system,the direct measurement values of the OPR-CRDS systemwere comparedwith the calculation results based on radical(OH,HO_(2),and RO_(2))reactions,and a good correlation was obtained between the measured and calculated values.Finally,the developed instrument was applied to obtain the comprehensive field observations at an urban site in the Yangtze River Delta(China)for 40 days,the time series and change characteristics of the P(O_(3))were obtained directly,and the good environmental adaptability and stability of the OPR-CRDS system were demonstrated.It is expected that the new instrument will be beneficial to investigations of the relationship between P(O_(3))and its precursors.展开更多
Non-dispersive infrared （NDIR） and cavity ring-down spectroscopy （CRDS） CO2 analyzers use 12CO2 isotopologue absorption lines and are insensitive to all or part of other CO2-related isotopologues. This may produce...Non-dispersive infrared （NDIR） and cavity ring-down spectroscopy （CRDS） CO2 analyzers use 12CO2 isotopologue absorption lines and are insensitive to all or part of other CO2-related isotopologues. This may produce biases in CO2 mole fraction measurements of a sample if its carbon isotopic composition deviates from that of the standard gases being used. To evaluate and compare the effects of carbon isotopic composition on NDIR and CRDS CO2 analyzers, we prepared three test sample air cylinders with varying carbon isotopic abundances and calibrated them against five standard cylinders with ambient carbon isotopic composition using CRDS and NDIR systems. We found that the CO2 mole fractions of the sample cylinders measured by G1301 （CRDS） were in good agreement with those measured by LoFlo （NDIR）. The CO2 values measured by both instruments were higher than that of a CO2 isotope measured by G2201i （CRDS） analyzer for a test cylinder with depleted carbon isotopic composition δ^13C =-36.828%0, whereas no obvious difference was found for other two test cylinders with 3 δ^13C=-8.630‰ and δ^13C=-15.380‰, respectively. According to the theoretical and experimental results, we concluded that the total CO2 mole fractions of samples with depleted isotopic compositions can be corrected on the basis of their 12CO2 values calibrated by standard gases using LoFlo and G1301 if the fi13C and fi180 values are known. Keywords NDIR and CRDS analyzers, Carbon isotopic effects, CO2 measurements展开更多
文摘本文在分析比较各种传统的维护数据库物理一致性的方法的基础上提出了一种既经济又实用的维护恢复策略,即延缓写盘的DLRU(Delay Least Recently Used)缓冲策略。这种方法改变了传统的LRU策略。LRU策略对于被排挤出缓冲区的块,若已改动,则立即将该块回写到盘上以便让出空间读进新块,而DLRU遇此情况,则将该快接到LRU链尾上(使它不被挤出的优先级最高),顺链继继找下去,直到找到未被改动过的块为止,在此过程中凡遇改过的块都依次接到链尾上,新读进的块就覆盖在所找到的未被改动的块上。如果整个缓冲区都已改动,则将缓冲区的所有块排序后一次性回写到外存上。如果系统在回写前发生了故障(各种故障),则用户键入一“作废”命令就将缓冲区中的全部块废除;如果用户在一系列的更新(增删改)操作后未发生异常,则键入“生效”命令,系统接到此命令后立即将缓冲区中所有块排序后写盘。当发生前述的缓冲区所有块都改过(且此时缓冲区已满)而用户至此未发生“生效”或“作废”命令,则系统暂停运行,强迫用户在“生效”和“作废”中必选一操作。为防止在回写过程中发生故障,此法要与其他方法配合使用。
文摘After four years of effort,the Beijing Institute of Control Engineering completed the development of the thirdgeneration camera type rendezvous and docking sensor(CRDS)for imaging and measurement of the spaceship and the target spacecraft at short range during rendezvous and docking.CRDS consists of a camera onboard the spaceship and a target designator onboard the target spacecraft.The relative
基金supported by the National Natural Science Foundation of China(Nos.62275250 and 61905003)the Natural Science Foundation of Anhui Province(No.2008085J20)+1 种基金the National Key R&D Program of China(No.2022YFC3700301)Anhui Provincial Key R&D Program(No.2022l07020022).
文摘A novel system for measuring net photochemical ozone production rates in the atmosphere based on cavity ring-down spectroscopy(OPR-CRDS)was developed.The system consists of two chambers(a reaction chamber and a reference chamber)and a dual-channel O_(x)-CRDS detector.To minimize the wall loss of O_(x)in the chambers,the inner surfaces of both chambers are coated with Teflon film.The performance of the OPR-CRDS system was characterized.It was found that even though the photolysis frequency(J value)decreased by 10%,the decrease in the P(O_(3))caused by the ultraviolet-blocking film coating was less than 3%.The two chambers had a good consistency in the mean residence time and the measurement of NO_(2)and O_(x)under the condition of no sunlight.The detection limit of the OPR-CRDS was determined to be 0.20 ppbv/hr.To further verify the accuracy of the system,the direct measurement values of the OPR-CRDS systemwere comparedwith the calculation results based on radical(OH,HO_(2),and RO_(2))reactions,and a good correlation was obtained between the measured and calculated values.Finally,the developed instrument was applied to obtain the comprehensive field observations at an urban site in the Yangtze River Delta(China)for 40 days,the time series and change characteristics of the P(O_(3))were obtained directly,and the good environmental adaptability and stability of the OPR-CRDS system were demonstrated.It is expected that the new instrument will be beneficial to investigations of the relationship between P(O_(3))and its precursors.
基金supported by the International Science&Technology Cooperation Program of China(Grant Nos.2015DFG21960&2011DFA21090)the National Natural Science Foundation of China(Grant Nos.40905066,41175116,41273097,41505108&41505123)+2 种基金the CMA Climate Change Program(Grant No.CCSF201331),the CMA Operational Fund(Grant No.CMAGJ2013M73)the Graduate Research and Innovation Projects of Universities in Jiangsu Province(Grant No.KYLX_0834)the CAMS Fundamental Research Funds(Grant Nos.2014Y005,2015Y002&2014Z004)
文摘Non-dispersive infrared （NDIR） and cavity ring-down spectroscopy （CRDS） CO2 analyzers use 12CO2 isotopologue absorption lines and are insensitive to all or part of other CO2-related isotopologues. This may produce biases in CO2 mole fraction measurements of a sample if its carbon isotopic composition deviates from that of the standard gases being used. To evaluate and compare the effects of carbon isotopic composition on NDIR and CRDS CO2 analyzers, we prepared three test sample air cylinders with varying carbon isotopic abundances and calibrated them against five standard cylinders with ambient carbon isotopic composition using CRDS and NDIR systems. We found that the CO2 mole fractions of the sample cylinders measured by G1301 （CRDS） were in good agreement with those measured by LoFlo （NDIR）. The CO2 values measured by both instruments were higher than that of a CO2 isotope measured by G2201i （CRDS） analyzer for a test cylinder with depleted carbon isotopic composition δ^13C =-36.828%0, whereas no obvious difference was found for other two test cylinders with 3 δ^13C=-8.630‰ and δ^13C=-15.380‰, respectively. According to the theoretical and experimental results, we concluded that the total CO2 mole fractions of samples with depleted isotopic compositions can be corrected on the basis of their 12CO2 values calibrated by standard gases using LoFlo and G1301 if the fi13C and fi180 values are known. Keywords NDIR and CRDS analyzers, Carbon isotopic effects, CO2 measurements
