A novel virtual material layer model based on the fractal theory was proposed to predict the natural frequencies of carbon fiber reinforced plastic composite bolted joints.Rough contact surfaces of composite bolted jo...A novel virtual material layer model based on the fractal theory was proposed to predict the natural frequencies of carbon fiber reinforced plastic composite bolted joints.Rough contact surfaces of composite bolted joints are modeled with this new proposed approach.Numerical and experimental modal analyses were conducted to validate the effectiveness of the proposed model.A good consistence is noted between the numerical and experimental results.To demonstrate the necessity of accurately modeling the rough contact surfaces in the prediction of natural frequencies,virtual material layer model was compared with the widely used traditional model based on the Master-Slave contact algorithm and experiments,respectively.Results show that the proposed model has a better agreement with experiments than the widely used traditional model(the prediction accuracy is raised by 8.77%when the pre-tightening torque is 0.5 N·m).Real contact area ratio A*of three different virtual material layers were calculated.Value of A*were discussed with dimensionless load P*,fractal dimension D and fractal roughness G.This work provides a new efficient way for accurately modeling the rough contact surfaces and predicting the natural frequencies of composite bolted joints,which can be used to help engineers in the dynamic design of composite materials.展开更多
Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than...Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than other approaches such as reducing the recording volume and multiplexing technology.However,the architecture of current MRLs is identical to that of recording data into physical layers with rigid space,which leads to either severe interlayer crosstalk or finite recording layers constrained by the short working distances of the objectives.Here,we propose the concept of hybrid-layer ODS,which can record optical information into a physical layer and multiple virtual layers by using high-orthogonality random meta-channels.In the virtual layer,32 images are experimentally reconstructed through holog-raphy,where their holographic phases are encoded into 16 printed images and complementary images in the physical layer,yielding a capacity of 2.5 Tbit cm^(-3).A higher capacity is achievable with more virtual layers,suggesting hybrid-layer ODS as a possible candidate for next-generation ODS.展开更多
Flume, which implements decentralized information flow control （DIFC）, allows a high security level process to ＂pre-create＂ secret files in a low security level directory. However, the pre-create mechanism makes s...Flume, which implements decentralized information flow control （DIFC）, allows a high security level process to ＂pre-create＂ secret files in a low security level directory. However, the pre-create mechanism makes some normal system calls unavailable, and moreover, it needs priori knowledge to create a large quantity of objects, which is difficult to estimate in practical operating systems. In this paper, we present an extended Flume file access control mechanism, named Effect, to substitute the mechanism of pre-create, which permits write operations （create, delete, and rename a file） on directories and creates a file access virtual layer that allocates operational views for each process with noninterference properties. In the end, we further present an analysis on the security of Effect. Our work makes it easier for multi-user to share confidential information in decentralized information flow control systems.展开更多
Network based data management is the backup/restore mechanism used in a data storage center. This paper presents a new network based data management-NDMP-Plus, a revision of network data management protocol. Component...Network based data management is the backup/restore mechanism used in a data storage center. This paper presents a new network based data management-NDMP-Plus, a revision of network data management protocol. Components and the working mechanism of the NDMP-Plus architecture are first discussed. Two new techniques in NDMP-Plus-virtual storage layer （VSL） and negotiation mechanism are then studied. VSL is a crucial component to achieve flexibility, and the negotiation mechanism is a key to improve performance. Furthermore, experiments are carried out to evaluate the performance of NDMP-Plus. The result suggests that NDMP-Plus has stronger flexibility and better performance than NDMP.展开更多
基金supported by National Natural Science Foundation of China(grant number 51975472)Intelligent Robotic in Ministry of Science and Technology of the People’s Republic of China(grant number 2017YFB1301703)Shaanxi New Star Plan of Science and Technology(grant number 2019KJXX-063)。
文摘A novel virtual material layer model based on the fractal theory was proposed to predict the natural frequencies of carbon fiber reinforced plastic composite bolted joints.Rough contact surfaces of composite bolted joints are modeled with this new proposed approach.Numerical and experimental modal analyses were conducted to validate the effectiveness of the proposed model.A good consistence is noted between the numerical and experimental results.To demonstrate the necessity of accurately modeling the rough contact surfaces in the prediction of natural frequencies,virtual material layer model was compared with the widely used traditional model based on the Master-Slave contact algorithm and experiments,respectively.Results show that the proposed model has a better agreement with experiments than the widely used traditional model(the prediction accuracy is raised by 8.77%when the pre-tightening torque is 0.5 N·m).Real contact area ratio A*of three different virtual material layers were calculated.Value of A*were discussed with dimensionless load P*,fractal dimension D and fractal roughness G.This work provides a new efficient way for accurately modeling the rough contact surfaces and predicting the natural frequencies of composite bolted joints,which can be used to help engineers in the dynamic design of composite materials.
基金the National Key Research and Development Program of China(2022YFB3607300)the National Natural Science Foundation of China(62322512 and 12134013)+3 种基金the Chinese Acad-emy of Sciences Project for Young Scientists in Basic Research(YSBR-049)support from the University of Science and Technology of China’s Center for Micro and Nanoscale Research and Fabricationsupported by the China Postdoctoral Science Foundation(2023M743364)supercomputing system in Hefei Advanced Computing Center and the Supercomputing Center of University of Science and Technology of China.
文摘Optical data storage(ODS)is a low-cost and high-durability counterpart of traditional electronic or mag-netic storage.As a means of enhancing ODS capacity,the multiple recording layer(MRL)method is more promising than other approaches such as reducing the recording volume and multiplexing technology.However,the architecture of current MRLs is identical to that of recording data into physical layers with rigid space,which leads to either severe interlayer crosstalk or finite recording layers constrained by the short working distances of the objectives.Here,we propose the concept of hybrid-layer ODS,which can record optical information into a physical layer and multiple virtual layers by using high-orthogonality random meta-channels.In the virtual layer,32 images are experimentally reconstructed through holog-raphy,where their holographic phases are encoded into 16 printed images and complementary images in the physical layer,yielding a capacity of 2.5 Tbit cm^(-3).A higher capacity is achievable with more virtual layers,suggesting hybrid-layer ODS as a possible candidate for next-generation ODS.
基金Supported by the National Natural Science Foundation of China(61003268,61103220,91118003,61173138,61170022)Hubei Provincial Natural Science Foundation(2010CDB08601)The Fundamental ResearchFunds for the Central Universities (3101038,274629)
文摘Flume, which implements decentralized information flow control （DIFC）, allows a high security level process to ＂pre-create＂ secret files in a low security level directory. However, the pre-create mechanism makes some normal system calls unavailable, and moreover, it needs priori knowledge to create a large quantity of objects, which is difficult to estimate in practical operating systems. In this paper, we present an extended Flume file access control mechanism, named Effect, to substitute the mechanism of pre-create, which permits write operations （create, delete, and rename a file） on directories and creates a file access virtual layer that allocates operational views for each process with noninterference properties. In the end, we further present an analysis on the security of Effect. Our work makes it easier for multi-user to share confidential information in decentralized information flow control systems.
基金Project supported by National Natural Science Foundation of China （Grant No. 60373088）, and National Defense Research Foundation（ Grant No .4131605）.Acknowledgements The ideas presented in this paper have benefited from many discussions with Tang Wenhui, Xia Tao and Zhang Ming. We would also like to thank Tang Fang and Liu Wei for their valuable suggestions to improve the paper.
文摘Network based data management is the backup/restore mechanism used in a data storage center. This paper presents a new network based data management-NDMP-Plus, a revision of network data management protocol. Components and the working mechanism of the NDMP-Plus architecture are first discussed. Two new techniques in NDMP-Plus-virtual storage layer （VSL） and negotiation mechanism are then studied. VSL is a crucial component to achieve flexibility, and the negotiation mechanism is a key to improve performance. Furthermore, experiments are carried out to evaluate the performance of NDMP-Plus. The result suggests that NDMP-Plus has stronger flexibility and better performance than NDMP.
