In wireless network simulation analysis, researchers tweak mobility metrics, such as the speed or the pause time of the nodes, to get different stability levels of the network. Meanwhile, in theoretical analysis, link...In wireless network simulation analysis, researchers tweak mobility metrics, such as the speed or the pause time of the nodes, to get different stability levels of the network. Meanwhile, in theoretical analysis, link failure rate is widely used to model the stability of a wireless network. This paper presents an analysis of a simplified mobility model and shows that the link failure rate is positively correlated with the average speed of nodes in this model. Though this result is based on a mobility model with many restrictions, a simulation evaluation suggests that the result still holds in the popular random waypoint model and random direction model. Based on this observation, this paper also encourages the use of link failure rate as mobility metric instead of the problematic pause time in future practice.展开更多
Location layout of aircraft assembly is an important factor affecting product quality.Most of the existing re-searches use the combination of finite element analysis and intelligent algorithm to optimize the location ...Location layout of aircraft assembly is an important factor affecting product quality.Most of the existing re-searches use the combination of finite element analysis and intelligent algorithm to optimize the location layout,which are limited by numerical simulation accuracy and the selection and improvement of intelligent algorithms.At present,the analysis and decision-making technology based on field data is gradually applied in aircraft manufacturing.Based on the perception data of intelligent assembly unit of aircraft parts,a regression model of multi-input and multioutput support vector machine with Gauss kernel function as radial basis function is established,and the hyperparameters of the model are optimized by hybrid particle swarm optimization genetic algorithm(PSO-GA).GA-MSVR,PSO-MSVR and PSOGA-MSVR model are constructed respectively,and their results show that PSOGA-MSVR model has the best performance.Finally,the design of the aircraft wing location layout is taken as an example to verify the effectiveness of the method.展开更多
Distributed Hash Tables (DHTs) were originated from the design of structured peer-to-peer (P2P) systems. A DHT provides a key-based lookup service similar to a hash table. In this paper, we present the detailed design...Distributed Hash Tables (DHTs) were originated from the design of structured peer-to-peer (P2P) systems. A DHT provides a key-based lookup service similar to a hash table. In this paper, we present the detailed design of a new DHT protocol, Tambour. The novelty of the protocol is that it uses parallel lookup to reduce retrive latency and bounds communication overhead to a dynamically adjusted routing table. Tambour estimates the probabilities of routing entries' liveness based on statistics of node lifetime history and evicts dead entries after lookup failures. When the network is unstable, more routing entries will be evicted in a given period of time, and the routing tables will be getting smaller which minimize the number of timeouts for later lookup requests. An experimental prototype of Tambour has been simulated and compared against two popular DHT protocols. Results show that Tambour outperforms the compared systems in terms of bandwith cost, lookup latency and the overall efficiency.展开更多
A class of time-varying delay impulsive reaction-diffusion tree grass-water-nitrogen system driven by Levy jump process is considered.First,we prove the existence and uniqueness of the global positive solution of the ...A class of time-varying delay impulsive reaction-diffusion tree grass-water-nitrogen system driven by Levy jump process is considered.First,we prove the existence and uniqueness of the global positive solution of the model by constructing the Lyapunov function.Secondly,several sufficient conditions for finite-time stability are given by using comparison theorem and mean impulse interval method.Finally,numerical simulations are carried out to verify the effectiveness of the theoretical analysis.展开更多
Ultra-high voltage direct current(UHVDC)transmission project in China is expanding,and the technology is increasingly maturing.The converter transformer is a crucial component in the UHVDC transmission projects,and it...Ultra-high voltage direct current(UHVDC)transmission project in China is expanding,and the technology is increasingly maturing.The converter transformer is a crucial component in the UHVDC transmission projects,and its valve-side bushing plays a key role in ensuring the stable operation of the power system.This paper investigates the electrical-thermal-stress distribution characteristics of the contact strip in an eccentric state.The research focuses on a section of the contact strip in the plug oil at the tail end of the bushing on the valve side of the converter.A three-dimensional finite element simulation model is established,and the contact strip contact resistance is used to define the contact strip eccentricity.The temperature rise platform of the contact strip was constructed to verify the precision of the simulation outcomes.The study investigated the variations in electric,thermal,and stress of contact strips in various eccentric states,as well as transient development,and the four stages of contact strip deformation were summarised using calculation results,providing quantitative analysis criteria for assessing the degree of deterioration of contact strips under eccentric conditions.Through the test and calculation,it can be seen that the contact resistance of the normal contact strip changes with the height in the form of a typical first-order exponential function.The contact resistance value is between 200 and 400μΩunder the actual mounting height;for the brand-new contact strip,the maximum temperature difference is 2.984 K without other interference;and after 15 min,the maximum displacements of the upper and lower half-ring strips reached are 84.3 and 83.7μm,respectively,due to the thermal expansion.The study results offer a theoretical foundation for understanding the failure of elastic electrical connection components in the bushing on the valve side of the converter.展开更多
This research is a case study of Shandong Public library with the application of a grounded theory to identify the perceived dimensions and the theoretical framework of organizational culture in the view of librarians...This research is a case study of Shandong Public library with the application of a grounded theory to identify the perceived dimensions and the theoretical framework of organizational culture in the view of librarians.Research found two dimensions which were internal cultural perception and external cultural perception.In the internal cultural perception,there include two notion areas,which are career orientation and personal characteristics of the individual;in the external cultural perception,there include five notion areas,which are social environment,architecture,systems,tasks and leadership.The theoretical framework of mechanisms of public librarians’ perception of organizational cultures is constructed.The study found two mechanisms of the dynamic evolution of organizational culture of public libraries:the first is the mechanism of individual internalization of cultures,and the other is the mechanism of the person-culture fit.展开更多
文摘In wireless network simulation analysis, researchers tweak mobility metrics, such as the speed or the pause time of the nodes, to get different stability levels of the network. Meanwhile, in theoretical analysis, link failure rate is widely used to model the stability of a wireless network. This paper presents an analysis of a simplified mobility model and shows that the link failure rate is positively correlated with the average speed of nodes in this model. Though this result is based on a mobility model with many restrictions, a simulation evaluation suggests that the result still holds in the popular random waypoint model and random direction model. Based on this observation, this paper also encourages the use of link failure rate as mobility metric instead of the problematic pause time in future practice.
基金supported by the Equipment Pre-research Project of China (No. 41423010202)
文摘Location layout of aircraft assembly is an important factor affecting product quality.Most of the existing re-searches use the combination of finite element analysis and intelligent algorithm to optimize the location layout,which are limited by numerical simulation accuracy and the selection and improvement of intelligent algorithms.At present,the analysis and decision-making technology based on field data is gradually applied in aircraft manufacturing.Based on the perception data of intelligent assembly unit of aircraft parts,a regression model of multi-input and multioutput support vector machine with Gauss kernel function as radial basis function is established,and the hyperparameters of the model are optimized by hybrid particle swarm optimization genetic algorithm(PSO-GA).GA-MSVR,PSO-MSVR and PSOGA-MSVR model are constructed respectively,and their results show that PSOGA-MSVR model has the best performance.Finally,the design of the aircraft wing location layout is taken as an example to verify the effectiveness of the method.
文摘Distributed Hash Tables (DHTs) were originated from the design of structured peer-to-peer (P2P) systems. A DHT provides a key-based lookup service similar to a hash table. In this paper, we present the detailed design of a new DHT protocol, Tambour. The novelty of the protocol is that it uses parallel lookup to reduce retrive latency and bounds communication overhead to a dynamically adjusted routing table. Tambour estimates the probabilities of routing entries' liveness based on statistics of node lifetime history and evicts dead entries after lookup failures. When the network is unstable, more routing entries will be evicted in a given period of time, and the routing tables will be getting smaller which minimize the number of timeouts for later lookup requests. An experimental prototype of Tambour has been simulated and compared against two popular DHT protocols. Results show that Tambour outperforms the compared systems in terms of bandwith cost, lookup latency and the overall efficiency.
文摘A class of time-varying delay impulsive reaction-diffusion tree grass-water-nitrogen system driven by Levy jump process is considered.First,we prove the existence and uniqueness of the global positive solution of the model by constructing the Lyapunov function.Secondly,several sufficient conditions for finite-time stability are given by using comparison theorem and mean impulse interval method.Finally,numerical simulations are carried out to verify the effectiveness of the theoretical analysis.
基金Science and Technology Project of State Grid Corporation of China,Grant/Award Number:5500-202255128A-1-1-ZN。
文摘Ultra-high voltage direct current(UHVDC)transmission project in China is expanding,and the technology is increasingly maturing.The converter transformer is a crucial component in the UHVDC transmission projects,and its valve-side bushing plays a key role in ensuring the stable operation of the power system.This paper investigates the electrical-thermal-stress distribution characteristics of the contact strip in an eccentric state.The research focuses on a section of the contact strip in the plug oil at the tail end of the bushing on the valve side of the converter.A three-dimensional finite element simulation model is established,and the contact strip contact resistance is used to define the contact strip eccentricity.The temperature rise platform of the contact strip was constructed to verify the precision of the simulation outcomes.The study investigated the variations in electric,thermal,and stress of contact strips in various eccentric states,as well as transient development,and the four stages of contact strip deformation were summarised using calculation results,providing quantitative analysis criteria for assessing the degree of deterioration of contact strips under eccentric conditions.Through the test and calculation,it can be seen that the contact resistance of the normal contact strip changes with the height in the form of a typical first-order exponential function.The contact resistance value is between 200 and 400μΩunder the actual mounting height;for the brand-new contact strip,the maximum temperature difference is 2.984 K without other interference;and after 15 min,the maximum displacements of the upper and lower half-ring strips reached are 84.3 and 83.7μm,respectively,due to the thermal expansion.The study results offer a theoretical foundation for understanding the failure of elastic electrical connection components in the bushing on the valve side of the converter.
基金an outcome of the project "Organizational culture of libraries from the perspective of management communication"(No.13BTQ001) supported by National Social Science Foundation of China
文摘This research is a case study of Shandong Public library with the application of a grounded theory to identify the perceived dimensions and the theoretical framework of organizational culture in the view of librarians.Research found two dimensions which were internal cultural perception and external cultural perception.In the internal cultural perception,there include two notion areas,which are career orientation and personal characteristics of the individual;in the external cultural perception,there include five notion areas,which are social environment,architecture,systems,tasks and leadership.The theoretical framework of mechanisms of public librarians’ perception of organizational cultures is constructed.The study found two mechanisms of the dynamic evolution of organizational culture of public libraries:the first is the mechanism of individual internalization of cultures,and the other is the mechanism of the person-culture fit.
