Epitaxial LiNbO_(3)(LNO)films are grown on n−type GaN semiconductor substrates,forming LNO/GaN p-n junctions.The current-voltage(I–V)and capacitance−voltage(C–V)characteristics of the junctions are studied.The I–V ...Epitaxial LiNbO_(3)(LNO)films are grown on n−type GaN semiconductor substrates,forming LNO/GaN p-n junctions.The current-voltage(I–V)and capacitance−voltage(C–V)characteristics of the junctions are studied.The I–V curve shows a clear rectifying property with a turn−on voltage of 2.4 V.For the forward voltages,the conduction mechanism transits from Schottky thermionic emission for low voltages to space-charge-limited current for large voltages.Reverse C–V characteristics exhibit a linear 1/C2 versus V plot,from which a built-in potential of 0.34 V is deduced.These results are explained using the energy-band structure of the LNO/GaN junction.展开更多
Information-centric networking （ICN） proposes a content-centric paradigm which has some attractive advantages, such as network load reduction, low dissemination latency, and energy efficiency. In this paper, based o...Information-centric networking （ICN） proposes a content-centric paradigm which has some attractive advantages, such as network load reduction, low dissemination latency, and energy efficiency. In this paper, based on the analytical model of ICN with receiver-driven transport protocol employing least-recently used （LRU） replacement policy, we derive expressions to compute the average content delivery time of the requests＇ arrival sequence of a single cache, and then we extend the expressions to a cascade of caches＇ scenario. From the expressions, we know the quantitative relationship among the delivery time, cache size and bandwidth. Our results, analyzing the trade-offs between performance and resources in ICN, can be used as a guide to design ICN and to evaluation its performance.展开更多
A novel methodology for prediction of network traffic, WPANFIS, which relies on wavelet packet transform （WPT） for multi-resolution analysis and adaptive neuro-fuzzy inference system （ANFIS） is proposed in this ar...A novel methodology for prediction of network traffic, WPANFIS, which relies on wavelet packet transform （WPT） for multi-resolution analysis and adaptive neuro-fuzzy inference system （ANFIS） is proposed in this article. The widespread existence of self-similarity in network traffic has been demonstrated in earlier studies, which exhibits both long range dependence （LRD） and short range dependence （SRD）. Also, it has been shown that wavelet decomposition is an effective tool for LRD decorrelation. The new method uses WPT as extension of wavelet transform which can decoorrelate LRD and make more precisely partition in the high-frequency section of the original traffic. Then ANFIS which can extract useful information from the original traffic is implemented in this study for better prediction performance of each decomposed non-stationary wavelet coefficients. Simulation results show that the proposed WPANFIS can achieve high prediction accuracy in real network traffic environment.展开更多
Background The assembled data from a population could provide information on health trends within the population.The aim of this research was to extract and know basic health information from an urban professional pop...Background The assembled data from a population could provide information on health trends within the population.The aim of this research was to extract and know basic health information from an urban professional population in Beijing.Methods Data analysis was carried out in a population who underwent a routine medical check-up and aged 〉20 years,including 30 058 individuals.General information,data from physical examinations and blood samples were collected in the same method.The health status was separated into three groups by the criteria generated in this study,i.e.,people with common chronic diseases,people in a sub-clinic situation,and healthy people.The proportion of both common diseases suffered and health risk distribution of different age groups were also analyzed.Results The proportion of people with common chronic diseases,in the sub-clinic group and in the healthy group was 28.6%,67.8% and 3.6% respectively.There were significant differences in the health situation in different age groups.Hypertension was on the top of list of self-reported diseases.The proportion of chronic diseases increased significantly in people after 35 years of age.Meanwhile,the proportion of sub-clinic conditions was decreasing at the same rate.The complex risk factors to health in this population were metabolic disturbances （61.3%）,risk for tumor （2.7%）,abnormal results of morphological examination （8.2%） and abnormal results of lab tests of serum （27.8%）.Conclusions Health information could be extracted from a complex data set from the heath check-ups of the general population.The information should be applied to support prevention and control chronic diseases as well as for directing intervention for patients with risk factors for disease.展开更多
One of the key research fields of content-centric networking （CCN） is to develop more efficient cache replacement policies to improve the hit ratio of CCN in-network caching. However, most of existing cache strategi...One of the key research fields of content-centric networking （CCN） is to develop more efficient cache replacement policies to improve the hit ratio of CCN in-network caching. However, most of existing cache strategies designed mainly based on the time or frequency of content access, can not properly deal with the problem of the dynamicity of content popularity in the network. In this paper, we propose a fast convergence caching replacement algorithm based on dynamic classification method for CCN, named as FCDC. It develops a dynamic classification method to reduce the time complexity of cache inquiry, which achieves a higher caching hit rate in comparison to random classification method under dynamic change of content popularity. Meanwhile, in order to relieve the influence brought about by dynamic content popularity, it designs a weighting function to speed up cache hit rate convergence in the CCN router. Experimental results show that the proposed scheme outperforms the replacement policies related to least recently used （LRU） and recent usage frequency （RUF） in cache hit rate and resiliency when content popularity in the network varies.展开更多
Network virtualization is a promising way to overcome the current ossification of the Intemet. It is essential challenge to find effective, efficient and robust embedding algorithms for recovering virtual network. The...Network virtualization is a promising way to overcome the current ossification of the Intemet. It is essential challenge to find effective, efficient and robust embedding algorithms for recovering virtual network. The virtual network mapping algorithm based on integer programming which was proposed months ago. But it did consider the faults of physical network resources, which is so called survivable virtual network embedding （VNE） problem. Previous strategies for enabling survivability in network virtualization focused on providing protection for the physical network or enhancing the virtual networks by providing backup physical resources in advance, and treated all the physical failures as link failures. In the article, a dynamic recovery method is proposed to solve the survivable virtual network embedding problem based on the integer programming VNE algorithm. The dynamic recovery method doesn＇t need to backup physical resources and it makes more substrate resources which can be used in the embedding. The dynamic recovery process will be activated only when physical failures occur. Different algorithms are used to recovery node and link failures. Simulations show that the method helps to recover almost all of physical failures by finding the substitute nodes and paths, and its performance is very close to that of pure VNE method without considering physical failures.展开更多
Echo state network （ESN） has become one of the most popular recurrent neural networks （RNN） for its good prediction performance of non-linear time series and simple training process. But several problems still pre...Echo state network （ESN） has become one of the most popular recurrent neural networks （RNN） for its good prediction performance of non-linear time series and simple training process. But several problems still prevent ESN from becoming a widely used tool. The most prominent problem is its high complexity with lots of random parameters. Aiming at this problem, a minimum complexity ESN model （MCESN） was proposed. In this paper, we proposed a new wavelet minimum complexity ESN model （WMCESN） to improve the prediction accuracy and increase the practical applicability. Our new model inherits the characters of minimum complexity ESN model using the fixed parameters and simple circle topology. We injected wavelet neurons to replace the original neurons in internal reservoir and designed a wavelet parameter matrix to reduce the computing time. By using different datasets, our new model performed better than the minimum complexity ESN model with normal neurons, but only utilized tiny time cost. We also used our own packets of transmission control protocol （TCP） and user datagram protocol （UDP） dataset to prove that our model can deal with the data packet bit prediction problem well.展开更多
The virtual network embedding/mapping problem is a core issue of the network virtualization. It＇s mainly concerned with how to map virtual network requests to the substrate network efficiently. Previous researches ma...The virtual network embedding/mapping problem is a core issue of the network virtualization. It＇s mainly concerned with how to map virtual network requests to the substrate network efficiently. Previous researches mainly focus on developing heuristic algorithms for general topology virtual network request. In this paper, we propose a new algorithm for the hub-and-spoke （HAS） topology virtual request. The characters of the HAS topology are exploited to develop the new algorithm. The simulation results show that the new algorithm greatly enhances the performance of revenue/cost （R/C） ratio while the HAS topology request arrives.展开更多
Because of its potential applications in agriculture, environment monitoring and so on, wireless underground sensor network（WUSN） has been researched more and more extensively in recent years. The main and most impo...Because of its potential applications in agriculture, environment monitoring and so on, wireless underground sensor network（WUSN） has been researched more and more extensively in recent years. The main and most important difference of WUSN to terrestrial wireless sensor network（WSN） is the channel characteristics, which determines the design methodology of it. In this paper, the propagation character of electromagnetic（EM） wave in the near surface WUSN is analyzed, as well as the path loss model of it is given. In addition, the influence of human＇s ankle to the channel characteristics of near surface WUSN is investigated by electromagnetic theory analysis, simulation and experiment. A novel path loss model of near surface WUSN which takes the interference of human＇s ankle into consideration is proposed. It is verified that the existing of human above the WUSN system may cause additional attenuation to the signal of near surface WUSN which propagates as lateral wave along the ground. Moreover, the relation of the attenuation and operating frequency is deduced, which gives a reference to extend the frequency band applied in WUSN.展开更多
基金Supported by the National Basic Research Development Program of China under Grant No.61363the National Science Foundation of China under Grant Nos.50932002 and 51102284the Shandong Provincial Natural Science Foundation under Grant No.ZR2010AQ017.
文摘Epitaxial LiNbO_(3)(LNO)films are grown on n−type GaN semiconductor substrates,forming LNO/GaN p-n junctions.The current-voltage(I–V)and capacitance−voltage(C–V)characteristics of the junctions are studied.The I–V curve shows a clear rectifying property with a turn−on voltage of 2.4 V.For the forward voltages,the conduction mechanism transits from Schottky thermionic emission for low voltages to space-charge-limited current for large voltages.Reverse C–V characteristics exhibit a linear 1/C2 versus V plot,from which a built-in potential of 0.34 V is deduced.These results are explained using the energy-band structure of the LNO/GaN junction.
基金supported by the National Basic Research Program of China(2012CB315801,2011CB302901)the Fundamental Research Funds for the Central Universities(2011RC0118)
文摘Information-centric networking （ICN） proposes a content-centric paradigm which has some attractive advantages, such as network load reduction, low dissemination latency, and energy efficiency. In this paper, based on the analytical model of ICN with receiver-driven transport protocol employing least-recently used （LRU） replacement policy, we derive expressions to compute the average content delivery time of the requests＇ arrival sequence of a single cache, and then we extend the expressions to a cascade of caches＇ scenario. From the expressions, we know the quantitative relationship among the delivery time, cache size and bandwidth. Our results, analyzing the trade-offs between performance and resources in ICN, can be used as a guide to design ICN and to evaluation its performance.
基金supported by the National Basic Research Program of China (2007CB310701)Research Fund for University Doctor Subject (20070013013)Chinese Universities Scientific Fund (2009RC0124)
文摘A novel methodology for prediction of network traffic, WPANFIS, which relies on wavelet packet transform （WPT） for multi-resolution analysis and adaptive neuro-fuzzy inference system （ANFIS） is proposed in this article. The widespread existence of self-similarity in network traffic has been demonstrated in earlier studies, which exhibits both long range dependence （LRD） and short range dependence （SRD）. Also, it has been shown that wavelet decomposition is an effective tool for LRD decorrelation. The new method uses WPT as extension of wavelet transform which can decoorrelate LRD and make more precisely partition in the high-frequency section of the original traffic. Then ANFIS which can extract useful information from the original traffic is implemented in this study for better prediction performance of each decomposed non-stationary wavelet coefficients. Simulation results show that the proposed WPANFIS can achieve high prediction accuracy in real network traffic environment.
文摘Background The assembled data from a population could provide information on health trends within the population.The aim of this research was to extract and know basic health information from an urban professional population in Beijing.Methods Data analysis was carried out in a population who underwent a routine medical check-up and aged 〉20 years,including 30 058 individuals.General information,data from physical examinations and blood samples were collected in the same method.The health status was separated into three groups by the criteria generated in this study,i.e.,people with common chronic diseases,people in a sub-clinic situation,and healthy people.The proportion of both common diseases suffered and health risk distribution of different age groups were also analyzed.Results The proportion of people with common chronic diseases,in the sub-clinic group and in the healthy group was 28.6%,67.8% and 3.6% respectively.There were significant differences in the health situation in different age groups.Hypertension was on the top of list of self-reported diseases.The proportion of chronic diseases increased significantly in people after 35 years of age.Meanwhile,the proportion of sub-clinic conditions was decreasing at the same rate.The complex risk factors to health in this population were metabolic disturbances （61.3%）,risk for tumor （2.7%）,abnormal results of morphological examination （8.2%） and abnormal results of lab tests of serum （27.8%）.Conclusions Health information could be extracted from a complex data set from the heath check-ups of the general population.The information should be applied to support prevention and control chronic diseases as well as for directing intervention for patients with risk factors for disease.
基金supported by the National Basic Research Program of China (2012CB315801, 2011CB302901)the Fundamental Research Funds for the Central Universities (2013RC0113)
文摘One of the key research fields of content-centric networking （CCN） is to develop more efficient cache replacement policies to improve the hit ratio of CCN in-network caching. However, most of existing cache strategies designed mainly based on the time or frequency of content access, can not properly deal with the problem of the dynamicity of content popularity in the network. In this paper, we propose a fast convergence caching replacement algorithm based on dynamic classification method for CCN, named as FCDC. It develops a dynamic classification method to reduce the time complexity of cache inquiry, which achieves a higher caching hit rate in comparison to random classification method under dynamic change of content popularity. Meanwhile, in order to relieve the influence brought about by dynamic content popularity, it designs a weighting function to speed up cache hit rate convergence in the CCN router. Experimental results show that the proposed scheme outperforms the replacement policies related to least recently used （LRU） and recent usage frequency （RUF） in cache hit rate and resiliency when content popularity in the network varies.
基金supported by the National Basic Research Programs of China(2012CB315801)
文摘Network virtualization is a promising way to overcome the current ossification of the Intemet. It is essential challenge to find effective, efficient and robust embedding algorithms for recovering virtual network. The virtual network mapping algorithm based on integer programming which was proposed months ago. But it did consider the faults of physical network resources, which is so called survivable virtual network embedding （VNE） problem. Previous strategies for enabling survivability in network virtualization focused on providing protection for the physical network or enhancing the virtual networks by providing backup physical resources in advance, and treated all the physical failures as link failures. In the article, a dynamic recovery method is proposed to solve the survivable virtual network embedding problem based on the integer programming VNE algorithm. The dynamic recovery method doesn＇t need to backup physical resources and it makes more substrate resources which can be used in the embedding. The dynamic recovery process will be activated only when physical failures occur. Different algorithms are used to recovery node and link failures. Simulations show that the method helps to recover almost all of physical failures by finding the substitute nodes and paths, and its performance is very close to that of pure VNE method without considering physical failures.
基金supported by the National Natural Science Foundation of China (61201153)the National Basic Research Program of China (2012CB315805)the National Key Science and Technology Projects (2010ZX03004-002-02)
文摘Echo state network （ESN） has become one of the most popular recurrent neural networks （RNN） for its good prediction performance of non-linear time series and simple training process. But several problems still prevent ESN from becoming a widely used tool. The most prominent problem is its high complexity with lots of random parameters. Aiming at this problem, a minimum complexity ESN model （MCESN） was proposed. In this paper, we proposed a new wavelet minimum complexity ESN model （WMCESN） to improve the prediction accuracy and increase the practical applicability. Our new model inherits the characters of minimum complexity ESN model using the fixed parameters and simple circle topology. We injected wavelet neurons to replace the original neurons in internal reservoir and designed a wavelet parameter matrix to reduce the computing time. By using different datasets, our new model performed better than the minimum complexity ESN model with normal neurons, but only utilized tiny time cost. We also used our own packets of transmission control protocol （TCP） and user datagram protocol （UDP） dataset to prove that our model can deal with the data packet bit prediction problem well.
基金supported by the National Basic Research Program of China (2011CB302901,2012CB315801)the Fundamental Research Funds for the Central Universities (2011RC0118)
文摘The virtual network embedding/mapping problem is a core issue of the network virtualization. It＇s mainly concerned with how to map virtual network requests to the substrate network efficiently. Previous researches mainly focus on developing heuristic algorithms for general topology virtual network request. In this paper, we propose a new algorithm for the hub-and-spoke （HAS） topology virtual request. The characters of the HAS topology are exploited to develop the new algorithm. The simulation results show that the new algorithm greatly enhances the performance of revenue/cost （R/C） ratio while the HAS topology request arrives.
基金supported by the National Natural Science Foundation of China(61001120)
文摘Because of its potential applications in agriculture, environment monitoring and so on, wireless underground sensor network（WUSN） has been researched more and more extensively in recent years. The main and most important difference of WUSN to terrestrial wireless sensor network（WSN） is the channel characteristics, which determines the design methodology of it. In this paper, the propagation character of electromagnetic（EM） wave in the near surface WUSN is analyzed, as well as the path loss model of it is given. In addition, the influence of human＇s ankle to the channel characteristics of near surface WUSN is investigated by electromagnetic theory analysis, simulation and experiment. A novel path loss model of near surface WUSN which takes the interference of human＇s ankle into consideration is proposed. It is verified that the existing of human above the WUSN system may cause additional attenuation to the signal of near surface WUSN which propagates as lateral wave along the ground. Moreover, the relation of the attenuation and operating frequency is deduced, which gives a reference to extend the frequency band applied in WUSN.
