This paper focuses on the intrusion classification of huge amounts of data in a network intrusion detection system. An intrusion detection model based on deep belief nets （DBN） is proposed to conduct intrusion detec...This paper focuses on the intrusion classification of huge amounts of data in a network intrusion detection system. An intrusion detection model based on deep belief nets （DBN） is proposed to conduct intrusion detection,and the principles regarding DBN are discussed.The DBN is composed of a multiple unsupervised restricted Boltzmann machine （RBM） and a supervised back propagation （BP）network.First,the DBN in the proposed model is pre-trained in a fast and greedy way,and each RBM is trained by the contrastive divergence algorithm.Secondly,the whole network is fine-tuned by the supervised BP algorithm,which is employed for classifying the low-dimensional features of the intrusion data generated by the last RBM layer simultaneously.The experimental results on the KDD CUP 1999 dataset demonstrate that the DBN using the RBM network with three or more layers outperforms the self-organizing maps （SOM）and neural network （NN）in intrusion classification.Therefore,the DBN is an efficient approach for intrusion detection in high-dimensional space.展开更多
Changes in soil chemistry after invasion by bracken(Pteridium aquilinum)have been studied in heathlands,but comparable studies in meadows are lacking.We investigated if bracken invasion into P-deficient meadows alters...Changes in soil chemistry after invasion by bracken(Pteridium aquilinum)have been studied in heathlands,but comparable studies in meadows are lacking.We investigated if bracken invasion into P-deficient meadows alters the soil nutrient-resource pool,as well as the mechanisms behind it linked to soil processes and bracken nutrition.Furthermore,we investigated how community composition responds to differences in soil chemistry before and after the invasion.Soil and plant material sampling,along with vegetation survey,were performed during bracken peak biomass.Data analyses included analysis of variance and canonical correspondence analysis(CCA).Bracken invasion increased soil P availability,soil organic C concentration,as well as C:N,C:S and N:S ratios,while decreasing Fe and Co concentrations.Bracken pinnae were rich in P,and its rhizomes were rich in K,whereas N:P of pinnae and rhizomes was low.CCA showed contrasting abundance patterns of frequent meadow species related to P and K availability.Holcus lanatus exhibited competitive advantage under extremely low P availability.Increase in P availability under bracken may have occurred through promoting the leaching of Fe and Al.By increasing P availability for its growth and increasing N limitation for other species,bracken can gain a competitive advantage from the soil resource-niche perspective.Its ability to increase soil P availability,along with the physiological mechanisms behind its high P acquisition efficiency,seem to differentiate bracken from other species of competitive ecological strategy,which are mainly confined to nutrient-rich environments.This enabled bracken to invade P-deficient meadows.展开更多
基金The National Key Technology R&D Program during the 12th Five-Year Plan Period(No.2013BAK01B02)the National Natural Science Foundation of China(No.61373176)the Scientific Research Projects of Shaanxi Educational Committee(No.14JK1693)
文摘This paper focuses on the intrusion classification of huge amounts of data in a network intrusion detection system. An intrusion detection model based on deep belief nets （DBN） is proposed to conduct intrusion detection,and the principles regarding DBN are discussed.The DBN is composed of a multiple unsupervised restricted Boltzmann machine （RBM） and a supervised back propagation （BP）network.First,the DBN in the proposed model is pre-trained in a fast and greedy way,and each RBM is trained by the contrastive divergence algorithm.Secondly,the whole network is fine-tuned by the supervised BP algorithm,which is employed for classifying the low-dimensional features of the intrusion data generated by the last RBM layer simultaneously.The experimental results on the KDD CUP 1999 dataset demonstrate that the DBN using the RBM network with three or more layers outperforms the self-organizing maps （SOM）and neural network （NN）in intrusion classification.Therefore,the DBN is an efficient approach for intrusion detection in high-dimensional space.
文摘Changes in soil chemistry after invasion by bracken(Pteridium aquilinum)have been studied in heathlands,but comparable studies in meadows are lacking.We investigated if bracken invasion into P-deficient meadows alters the soil nutrient-resource pool,as well as the mechanisms behind it linked to soil processes and bracken nutrition.Furthermore,we investigated how community composition responds to differences in soil chemistry before and after the invasion.Soil and plant material sampling,along with vegetation survey,were performed during bracken peak biomass.Data analyses included analysis of variance and canonical correspondence analysis(CCA).Bracken invasion increased soil P availability,soil organic C concentration,as well as C:N,C:S and N:S ratios,while decreasing Fe and Co concentrations.Bracken pinnae were rich in P,and its rhizomes were rich in K,whereas N:P of pinnae and rhizomes was low.CCA showed contrasting abundance patterns of frequent meadow species related to P and K availability.Holcus lanatus exhibited competitive advantage under extremely low P availability.Increase in P availability under bracken may have occurred through promoting the leaching of Fe and Al.By increasing P availability for its growth and increasing N limitation for other species,bracken can gain a competitive advantage from the soil resource-niche perspective.Its ability to increase soil P availability,along with the physiological mechanisms behind its high P acquisition efficiency,seem to differentiate bracken from other species of competitive ecological strategy,which are mainly confined to nutrient-rich environments.This enabled bracken to invade P-deficient meadows.
