Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sed...Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sediment input has been plotted with respect to each grain size fraction. Several fill-scour thresholds in sediment input have been identified from these graphs. It was found that the fill-scour threshold in sediment input decreases with the increase in fraction grain size. The correlation coefficient between channel sedimentation and sediment input becomes larger with the increasing fraction grain size, indicating that channel sedimentation depends more on coarser grain size fractions than on smaller ones. The fraction channel sedimentation induced by unit change of fraction sediment input increases with grain size. Of the input of sediment larger than 0.025 mm, 43.73% was deposited on the channel, and for inputs of sediments larger than 0.05 mm and larger than 0.10 mm, 76.61% and 97.68% were deposited on the channel, respectively. Thus, for reduction of each ton of sediment larger than 0.10 mm from the drainage basin, the resultant reduction in channel sedimentation in the lower Yellow River would be 1.275 times that for the sediment larger than 0.10 mm, and 2.234 times that for the sediment larger than 0.025 mm. Therefore, if the erosion and sediment control measures are enforced in the areas where >0.05 or >0.10 mm sediment is produced, then the best beneficial will be achieved in reducing sedimentation in the lower Yellow River.展开更多
Battery energy storage systems(BESSs)can provide instantaneous support for frequency regulation(FR)because of their fast response characteristics.However,purely pursuing a better FR effect calls for continually rapid ...Battery energy storage systems(BESSs)can provide instantaneous support for frequency regulation(FR)because of their fast response characteristics.However,purely pursuing a better FR effect calls for continually rapid cycles of BESSs,which shortens their lifetime and deteriorates the operational economy.To coordinate the lifespan savings and the FR effect,this paper presents a control strategy for the FR of BESSs based on fuzzy logic and hierarchical controllers.The fuzzy logic controller improves the effect of FR by adjusting the charging/discharging power of the BESS with a higher response speed and precision based on the area control error(ACE)signal and the change rate of ACE in a non-linear way.Hierarchical controllers effectively reduce the life loss by optimizing the depth of discharge,which ensures that the state of charge(SOC)of BESS is always in the optimal operating range,and the total FR cost is the lowest at this time.The proposed method can achieve the optimal balance between ACE reduction and operational economy of BESS.The effectiveness of the proposed strategy is verified in a two-area power system.展开更多
微网利用光伏、风机等可再生能源发电(renewable energy source of electricity,RES-E)并与能量存储系统配合向本地负荷供电,可以减小能量传输损耗以及大电网扰动的影响。然而,微网中的可再生能源分布式电源出力与负荷逆向分布,如何利...微网利用光伏、风机等可再生能源发电(renewable energy source of electricity,RES-E)并与能量存储系统配合向本地负荷供电,可以减小能量传输损耗以及大电网扰动的影响。然而,微网中的可再生能源分布式电源出力与负荷逆向分布,如何利用储能元件实现能源就地高效利用、避免大量过剩功率入网是当前微网发展重点之一。针对这一问题,该文提出一种可变阈值的自动适应控制方法,采用自适应智能技术控制储能元件的即时充放电功率,提高电能分配效率,实现对于负荷的"削峰填谷"。文中利用现场测得的RES数据对提出的方法进行验证,结果表明与传统利用固定阈值和需要精确预测的方法相比提出的方法在不需要RES和负荷预测数据的情况下,可以更有效减小负荷峰值,得到更加平滑的负荷曲线,同时最大程度地利用本地RES能源。展开更多
The recent advances in remote sensing and computer techniques give birth to the explosive growth of remote sensing images.The emergence of cloud storage has brought new opportunities for storage and management of mass...The recent advances in remote sensing and computer techniques give birth to the explosive growth of remote sensing images.The emergence of cloud storage has brought new opportunities for storage and management of massive remote sensing images with its large storage space,cost savings.However,the openness of cloud brings challenges for image data security.In this paper,we propose a weighted image sharing scheme to ensure the security of remote sensing in cloud environment,which takes the weights of participants(i.e.,cloud service providers)into consideration.An extended Mignotte sequence is constructed according to the weights of participants,and we can generate image shadow shares based on the hash value which can be obtained from gray value of remote sensing images.Then we store the shadows in every cloud service provider,respectively.At last,we restore the remote sensing image based on the Chinese Remainder Theorem.Experimental results show the proposed scheme can effectively realize the secure storage of remote sensing images in the cloud.The experiment also shows that no matter weight values,each service providers only needs to save one share,which simplifies the management and usage,it also reduces the transmission of secret information,strengthens the security and practicality of this scheme.展开更多
To tackle the problem that wells that are deployed in a specific pattern based on the requirements of gas reservoir development are not suitable for gas storage,we have conducted concentrically circular injection and ...To tackle the problem that wells that are deployed in a specific pattern based on the requirements of gas reservoir development are not suitable for gas storage,we have conducted concentrically circular injection and production simulation experiments for gas storage,discovered the existence of a threshold radius,denoted by Rt,and derived the expression for Rt.Based on the analysis and discussion results,we propose a strategy for deploying gas storage wells in specific patterns.The expression for Rt shows that it is affected by factors such as the gas storage gas production/injection time,the upper pressure limit,the lower pressure limit,the bottomhole flow pressure at the ends of injection and production,the and permeability.The analysis and discussion results show that the Rt of a gas storage facility is much smaller than the Rt for gas reservoir development.In the gas storage facilities in China,the Rt for gas production is less than the Rt for the gas injection,and Rt increases with the difference in the operating pressure and with permeability K.Based on the characteristics of Rt,we propose three suggestions for gas storage well pattern deployment:(1)calculate Rt according to the designed functions of the gas storage facility and deploy the well pattern according to Rt;(2)deploy sparser,large-wellbore patterns in high-permeability areas and denser,small-wellbore patterns in high-permeability areas;and(3)achieve the gas injection well pattern by new drilling,and the gas production well pattern through a combination of the gas injection well pattern and old wells.By assessing a gas storage facility with a perfect well pattern after a number of adjustments,we found that the Rt of the 12 wells calculated in this paper is basically close to the corresponding actual radius,which validates our method.The results of this study provide a methodological basis for well pattern deployment in new gas storage construction.展开更多
This paper proposes a security enhancement scheme for disaster tolerant systems based on trusted computing technology which combines with the idea of distributed threshold storage. This scheme takes advantage of a tru...This paper proposes a security enhancement scheme for disaster tolerant systems based on trusted computing technology which combines with the idea of distributed threshold storage. This scheme takes advantage of a trusted computing platform with a trusted computing module, which has excellent features such as security storage, remote attestation, and so on. These features effectively ensure trustworthiness of the disaster tolerant point. Furthermore, distributed storage based on Erasure code not only disposes the storage problem about a great deal of data, but also preferably avoids one node invalidation, alleviates network load and deals with joint cheat and many other security problems. Consequently, those security enhancement technologies provide mass data with global security protection during the course of disaster tolerance.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 50725930) Chinese Ministry for Science and Technology (Grant No. 2006BA06B03)
文摘Based on the data of suspended sediment transport and channel sedimentation in various grain size fractions in the period of 1962―1985, the relationship between channel sedimentation in the lower Yellow River and sediment input has been plotted with respect to each grain size fraction. Several fill-scour thresholds in sediment input have been identified from these graphs. It was found that the fill-scour threshold in sediment input decreases with the increase in fraction grain size. The correlation coefficient between channel sedimentation and sediment input becomes larger with the increasing fraction grain size, indicating that channel sedimentation depends more on coarser grain size fractions than on smaller ones. The fraction channel sedimentation induced by unit change of fraction sediment input increases with grain size. Of the input of sediment larger than 0.025 mm, 43.73% was deposited on the channel, and for inputs of sediments larger than 0.05 mm and larger than 0.10 mm, 76.61% and 97.68% were deposited on the channel, respectively. Thus, for reduction of each ton of sediment larger than 0.10 mm from the drainage basin, the resultant reduction in channel sedimentation in the lower Yellow River would be 1.275 times that for the sediment larger than 0.10 mm, and 2.234 times that for the sediment larger than 0.025 mm. Therefore, if the erosion and sediment control measures are enforced in the areas where >0.05 or >0.10 mm sediment is produced, then the best beneficial will be achieved in reducing sedimentation in the lower Yellow River.
基金This work was supported by Open Research Project of State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments,Tsinghua University(No.SKLD20M20)Xinjiang Uygur Autonomous Region Natural Science Key Project of University Research Program(No.XJEDU2020I004).
文摘Battery energy storage systems(BESSs)can provide instantaneous support for frequency regulation(FR)because of their fast response characteristics.However,purely pursuing a better FR effect calls for continually rapid cycles of BESSs,which shortens their lifetime and deteriorates the operational economy.To coordinate the lifespan savings and the FR effect,this paper presents a control strategy for the FR of BESSs based on fuzzy logic and hierarchical controllers.The fuzzy logic controller improves the effect of FR by adjusting the charging/discharging power of the BESS with a higher response speed and precision based on the area control error(ACE)signal and the change rate of ACE in a non-linear way.Hierarchical controllers effectively reduce the life loss by optimizing the depth of discharge,which ensures that the state of charge(SOC)of BESS is always in the optimal operating range,and the total FR cost is the lowest at this time.The proposed method can achieve the optimal balance between ACE reduction and operational economy of BESS.The effectiveness of the proposed strategy is verified in a two-area power system.
文摘微网利用光伏、风机等可再生能源发电(renewable energy source of electricity,RES-E)并与能量存储系统配合向本地负荷供电,可以减小能量传输损耗以及大电网扰动的影响。然而,微网中的可再生能源分布式电源出力与负荷逆向分布,如何利用储能元件实现能源就地高效利用、避免大量过剩功率入网是当前微网发展重点之一。针对这一问题,该文提出一种可变阈值的自动适应控制方法,采用自适应智能技术控制储能元件的即时充放电功率,提高电能分配效率,实现对于负荷的"削峰填谷"。文中利用现场测得的RES数据对提出的方法进行验证,结果表明与传统利用固定阈值和需要精确预测的方法相比提出的方法在不需要RES和负荷预测数据的情况下,可以更有效减小负荷峰值,得到更加平滑的负荷曲线,同时最大程度地利用本地RES能源。
基金This research was partly supported by(National Natural Science Foundation of China under 41671431,61572421and Shanghai Science and Technology Commission Project 15590501900.
文摘The recent advances in remote sensing and computer techniques give birth to the explosive growth of remote sensing images.The emergence of cloud storage has brought new opportunities for storage and management of massive remote sensing images with its large storage space,cost savings.However,the openness of cloud brings challenges for image data security.In this paper,we propose a weighted image sharing scheme to ensure the security of remote sensing in cloud environment,which takes the weights of participants(i.e.,cloud service providers)into consideration.An extended Mignotte sequence is constructed according to the weights of participants,and we can generate image shadow shares based on the hash value which can be obtained from gray value of remote sensing images.Then we store the shadows in every cloud service provider,respectively.At last,we restore the remote sensing image based on the Chinese Remainder Theorem.Experimental results show the proposed scheme can effectively realize the secure storage of remote sensing images in the cloud.The experiment also shows that no matter weight values,each service providers only needs to save one share,which simplifies the management and usage,it also reduces the transmission of secret information,strengthens the security and practicality of this scheme.
基金granted by the National Key Research and Development Project grant number 2017YFC0805801the Chinese Academy of Engineering Major Consulting Project grant number 2017-ZD-03。
文摘To tackle the problem that wells that are deployed in a specific pattern based on the requirements of gas reservoir development are not suitable for gas storage,we have conducted concentrically circular injection and production simulation experiments for gas storage,discovered the existence of a threshold radius,denoted by Rt,and derived the expression for Rt.Based on the analysis and discussion results,we propose a strategy for deploying gas storage wells in specific patterns.The expression for Rt shows that it is affected by factors such as the gas storage gas production/injection time,the upper pressure limit,the lower pressure limit,the bottomhole flow pressure at the ends of injection and production,the and permeability.The analysis and discussion results show that the Rt of a gas storage facility is much smaller than the Rt for gas reservoir development.In the gas storage facilities in China,the Rt for gas production is less than the Rt for the gas injection,and Rt increases with the difference in the operating pressure and with permeability K.Based on the characteristics of Rt,we propose three suggestions for gas storage well pattern deployment:(1)calculate Rt according to the designed functions of the gas storage facility and deploy the well pattern according to Rt;(2)deploy sparser,large-wellbore patterns in high-permeability areas and denser,small-wellbore patterns in high-permeability areas;and(3)achieve the gas injection well pattern by new drilling,and the gas production well pattern through a combination of the gas injection well pattern and old wells.By assessing a gas storage facility with a perfect well pattern after a number of adjustments,we found that the Rt of the 12 wells calculated in this paper is basically close to the corresponding actual radius,which validates our method.The results of this study provide a methodological basis for well pattern deployment in new gas storage construction.
基金Supported by the National High Technology Research and Development Program of China (863 Program) (2008AA01Z404)the Science and Technical Key Project of Ministry of Education (108087)the Scientific and Technological Project of Wuhan City (200810321130)
文摘This paper proposes a security enhancement scheme for disaster tolerant systems based on trusted computing technology which combines with the idea of distributed threshold storage. This scheme takes advantage of a trusted computing platform with a trusted computing module, which has excellent features such as security storage, remote attestation, and so on. These features effectively ensure trustworthiness of the disaster tolerant point. Furthermore, distributed storage based on Erasure code not only disposes the storage problem about a great deal of data, but also preferably avoids one node invalidation, alleviates network load and deals with joint cheat and many other security problems. Consequently, those security enhancement technologies provide mass data with global security protection during the course of disaster tolerance.
