Temperature is one of the important loads for designing slab track. The characteristic of slab track tem- perature varies greatly with different regional climates. In this work, a bi-block slab track model was built u...Temperature is one of the important loads for designing slab track. The characteristic of slab track tem- perature varies greatly with different regional climates. In this work, a bi-block slab track model was built under outdoor conditions in Chengdu area; the statistical characteristic of temperature gradient in track slab and the relationship between temperature gradient and surface air temperature were tested and analyzed. The results show that the track slab temperature gradient will vary periodically according to the surface air temperature, and show a clear nonlinearity along the height direction. The temperature gradient distribution is extremely uneven： the temperature gradient in the top part of the track slab is larger than that in the bottom part; the most frequently occurring temperature gradient of the track slab is around -3.5 ℃/m and more than 75 % locates in the level -10 to 10 ℃/m; concrete with a relatively good heat exchange condition with the surrounding air has a narrower band distribution. In addition, the frequency distribution histogram should exclude the time zone from 00：00 to 06：00 because there is almost no traffic in this period. The amplitude of track slab temperature variation is obviously lower than that of the air temperature variation, and the former is approximately linear with the latter.展开更多
In the multistage imaging processing for SAR digital imaging and applications ofSAR imagery,extraction of luminance edge for the SAR imageis often required.It is well studiedto extract the luminance edge for ordinary ...In the multistage imaging processing for SAR digital imaging and applications ofSAR imagery,extraction of luminance edge for the SAR imageis often required.It is well studiedto extract the luminance edge for ordinary images,The methods using gradient are effective andcommonly used.Because of the serious noise of coherent speckle exists in SAR images,somepeople believe that edge extraction by using gradient for SAR imagery gives poor results.Inthis paper,we have derived a rather ideal method for the extraction of luminance edge for SARimagery with the consideration of the characteristics of SAR imagery.This method uses therelative average gradient and combines detection with tracking.展开更多
Three typhoon cases are selected to conduct a series of simulations that are initialized from sequential analyses. The results show that the forecast error in crucial area where a tropical cyclone(TC) interactes with ...Three typhoon cases are selected to conduct a series of simulations that are initialized from sequential analyses. The results show that the forecast error in crucial area where a tropical cyclone(TC) interactes with the upstream trough is highly correlated to the track forecast error after the TC recurvature. Furthermore, sensitivity experiments confirm that the developments of the midlatitude downstream circulations and then the TC track after its recurvature are highly sensitive to the TC intensity and its location relative to the upstream trough, which can give an example or one way of sensitivity of the TC track to the TC-trough interaction. If the TC interacts with the upstream trough more strongly(e.g., the TC being intensified or getting closer to the upstream trough), the downstream circulations will be more meridional, thus the TC track will be more northerly and westerly; otherwise, the downstream circulations will be more zonal, and the TC track will be more southerly and easterly.展开更多
In this paper,the authors propose a distributed gradient tracking algorithm with compressed communication to address an aggregative optimization problem under communication constraints.The problem involves minimizing ...In this paper,the authors propose a distributed gradient tracking algorithm with compressed communication to address an aggregative optimization problem under communication constraints.The problem involves minimizing the sum of local cost functions,where each cost function depends on both local and global state variables.The authors aim to solve this optimization problem through local computation and efficient communication among agents in a network,without the need for a central coordinator.The proposed algorithm combines the variable tracking method to estimate global state variables and a compressed communication scheme to reduce communication costs during the optimization process.Among which,the compressed scheme can encompass both biased and unbiased compressors.Despite the loss of some transmitting information due to quantization,the proposed algorithm can still achieve the exact optimal solution with a linear convergence rate.The authors validate the theoretical results through simulation experiments on an optimal placement problem.展开更多
为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以...为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以光伏分压注水泵为基础,通过分压压力缸对管网来水做功,实现高低压井能量转换;分析光伏分压注水泵的电流环、电压环,利用最优梯度的MPPT算法令光伏分压注水泵持续处于最大功率点状态下,当光伏分压注水泵运行功率产生变化时,调节电流环输出、控制主开关管占比、调节光伏分压注水泵的输出功率;通过实时监测和调整PWM脉冲宽度调制信号占空比,实现光伏分压注水泵闭环控制,由此提高水泵的能量转换效率。实验表明,该方法可以有效使水泵运行稳定性得以增强,并实现油气田管网注水量的合理有效控制,且有效提升油气田注水管注水效率。展开更多
基金supported by the National Key Basic Research Program of China (973 Program) (2013CB036202)the National Natural Science Foundation of China (51008258)Fundamental Research Funds for the Central Universities (SWJTU12CX065)
文摘Temperature is one of the important loads for designing slab track. The characteristic of slab track tem- perature varies greatly with different regional climates. In this work, a bi-block slab track model was built under outdoor conditions in Chengdu area; the statistical characteristic of temperature gradient in track slab and the relationship between temperature gradient and surface air temperature were tested and analyzed. The results show that the track slab temperature gradient will vary periodically according to the surface air temperature, and show a clear nonlinearity along the height direction. The temperature gradient distribution is extremely uneven： the temperature gradient in the top part of the track slab is larger than that in the bottom part; the most frequently occurring temperature gradient of the track slab is around -3.5 ℃/m and more than 75 % locates in the level -10 to 10 ℃/m; concrete with a relatively good heat exchange condition with the surrounding air has a narrower band distribution. In addition, the frequency distribution histogram should exclude the time zone from 00：00 to 06：00 because there is almost no traffic in this period. The amplitude of track slab temperature variation is obviously lower than that of the air temperature variation, and the former is approximately linear with the latter.
文摘In the multistage imaging processing for SAR digital imaging and applications ofSAR imagery,extraction of luminance edge for the SAR imageis often required.It is well studiedto extract the luminance edge for ordinary images,The methods using gradient are effective andcommonly used.Because of the serious noise of coherent speckle exists in SAR images,somepeople believe that edge extraction by using gradient for SAR imagery gives poor results.Inthis paper,we have derived a rather ideal method for the extraction of luminance edge for SARimagery with the consideration of the characteristics of SAR imagery.This method uses therelative average gradient and combines detection with tracking.
基金International Cooperating Program of Science and Technology(2010DFA24650)National Natural Science Foundation of China(41175061)
文摘Three typhoon cases are selected to conduct a series of simulations that are initialized from sequential analyses. The results show that the forecast error in crucial area where a tropical cyclone(TC) interactes with the upstream trough is highly correlated to the track forecast error after the TC recurvature. Furthermore, sensitivity experiments confirm that the developments of the midlatitude downstream circulations and then the TC track after its recurvature are highly sensitive to the TC intensity and its location relative to the upstream trough, which can give an example or one way of sensitivity of the TC track to the TC-trough interaction. If the TC interacts with the upstream trough more strongly(e.g., the TC being intensified or getting closer to the upstream trough), the downstream circulations will be more meridional, thus the TC track will be more northerly and westerly; otherwise, the downstream circulations will be more zonal, and the TC track will be more southerly and easterly.
基金supported by the National Key Research and Development Program of China under Grant No.2022YFA1004701the National Natural Science Foundation of China under Grant No.72271187+1 种基金the Fundamental Research Funds for the Central Universitiespartially by Shanghai Municipal Science and Technology Major Project under Grant No.2021SHZDZX0100。
文摘In this paper,the authors propose a distributed gradient tracking algorithm with compressed communication to address an aggregative optimization problem under communication constraints.The problem involves minimizing the sum of local cost functions,where each cost function depends on both local and global state variables.The authors aim to solve this optimization problem through local computation and efficient communication among agents in a network,without the need for a central coordinator.The proposed algorithm combines the variable tracking method to estimate global state variables and a compressed communication scheme to reduce communication costs during the optimization process.Among which,the compressed scheme can encompass both biased and unbiased compressors.Despite the loss of some transmitting information due to quantization,the proposed algorithm can still achieve the exact optimal solution with a linear convergence rate.The authors validate the theoretical results through simulation experiments on an optimal placement problem.
文摘为确保光伏分压注水泵在各种油气管环境条件下都能以最大功率输出,保持油气田注水管网分压的稳定性,提出基于最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法的油气田注水管网分压闭环控制方法。设计油气田注水管网分压技术,以光伏分压注水泵为基础,通过分压压力缸对管网来水做功,实现高低压井能量转换;分析光伏分压注水泵的电流环、电压环,利用最优梯度的MPPT算法令光伏分压注水泵持续处于最大功率点状态下,当光伏分压注水泵运行功率产生变化时,调节电流环输出、控制主开关管占比、调节光伏分压注水泵的输出功率;通过实时监测和调整PWM脉冲宽度调制信号占空比,实现光伏分压注水泵闭环控制,由此提高水泵的能量转换效率。实验表明,该方法可以有效使水泵运行稳定性得以增强,并实现油气田管网注水量的合理有效控制,且有效提升油气田注水管注水效率。
