A Real-Time and Ubiquitous Network Attack Detection Based on Deep Belief Network and Support Vector Machine

In recent years, network traffic data have become larger and more complex, leading to higher possibilities of network intrusion. Traditional intrusion detection methods face difficulty in processing high-speed network data and cannot detect currently unknown attacks. Therefore, this paper proposes a network attack detection method combining a flow calculation and deep learning. The method consists of two parts: a real-time detection algorithm based on flow calculations and frequent patterns and a classification algorithm based on the deep belief network and support vector machine(DBN-SVM). Sliding window(SW) stream data processing enables real-time detection, and the DBN-SVM algorithm can improve classification accuracy. Finally, to verify the proposed method, a system is implemented.Based on the CICIDS2017 open source data set, a series of comparative experiments are conducted. The method's real-time detection efficiency is higher than that of traditional machine learning algorithms. The attack classification accuracy is 0.7 percentage points higher than that of a DBN, which is 2 percentage points higher than that of the integrated algorithm boosting and bagging methods. Hence, it is suitable for the real-time detection of high-speed network intrusions.

A high H_2 evolution rate under visible light of a CdS/TiO_2@Ni S catalyst due to a directional electron transfer between the phases

The photocatalytic activity of CdS can be greatly improved by co-modification of NiS and TiO_2 materials; furthermore the order of connection affects much. A directional electron transfer route via CdS → TiO_2→ NiS is found crucial to the enhancement of ternary catalyst, where TiO_2 acts as an electron reservoir and Ni S works as an effective cocatalyst. Cd S/TiO_2@Ni S with Ni S loaded on TiO_2 has an activity of H_2 evolution 2.5 times higher than NiS@Cd S/TiO_2 with Ni S pre-loaded on Cd S. Faster e-/h+separation rates is obtained of Cd S/TiO_2@Ni S under visible light than under extra UV light irradiation, which in turn demonstrates the importance of directional electron transfer route.

Insight into SO_(2) poisoning and regeneration of one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO_(x) by NH_(3)

The effects of SO_(2) on an one-pot synthesized Cu-SSZ-13 catalyst for selective reduction of NO_(x) by NH_(3) were examined.The addition of SO_(2) inhibited NO_(x) conversion significantly below 300℃,while no effect on NO_(x) conversion was observed above 300℃.TGA,TPD,and XPS results showed that the deactivation was caused by the formation of(NH4)2SO_(4),SO_(2) chemisorption on the isolated Cu^(2+)ion sites,as well as the formation of CuSO_(4)-like species.Among them,the site-blocking effect of(NH_(4))_(2)SO_(4) on Cu^(2+)was the primary reason for deactivation.Fortunately,89%of deNO_(x) activity of the poisoned catalyst was recovered after thermal treatment at 500℃ in air,where(NH_(4))_(2)SO_(4) was completely decomposed.The activity was further recovered with regeneration temperature increasing to 600℃,removing the adsorbed SO_(2) on the Cu^(2+)sites.The regeneration at 600℃ could not recover the activity completely,because of the high stability of CuSO_(4)-like species.

A Study on the Effects of Carrier Gases on the Structure and Morphology of Carbon Nanotubes Prepared by Pyrolysis of Ferrocene and C_2H_2 Mixture

Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.

Sustainable H2 production from ethanol steam reforming over a macro-mesoporous Ni/Mg-Al-O catalytic monolith

A macro-meso-porous monolithic Ni-based catalyst was prepared via an impregnation route using polystyrene foam as the template and then used in the steam reforming of ethanol to produce a H2-rich gas. The Ni/Mg-A1 catalyst has a hierarchically macro-meso-porous structure as indicated by photographs and scanning electron microscopy （SEM）. The surface area of the catalyst was 230 m2＂ g 1 and the Ni dispersion was 5.62%. Compared to the pelletized sample that was prepared without a template, the macro-meso-porous Ni/Mg-A1 monolith exhibited superior reactivity in terms of H2 production and also had lower CH4 yields at 700~C and 800℃. Furthermore, the monolithic catalyst maintained excellent activity and H2 selectivity after 100-h on-stream at 700℃, as well as good resistance to coking and metal sintering.

CARBON NANOTUBES VIA METHANE DECOMPOSITION ON AN ALUMINA SUPPORTED COBALT AEROGEL CATALYST

An alumina-supported cobalt aerogel catalyst prepared from a sol-gel and a supercritical drying method was used in the catalytic decomposition of methane. The physical-chemical properties of the catalyst were characterized and its activity for methane decomposition was investigated. The effects of calcination and reaction temperatures on the activity of the catalyst and the morphology of the carbon nanotubes produced were discussed. A CoAl2O4 spinel structure formed in the calcined catalyst. The quantity of the nanotubes produced in the reaction increases with the amount of cobalt in the reduced catalyst. A higher reaction temperature leads to a higher reaction rate, though faster deactivation of the catalyst occurs with the change. The carbon nanotubes grown on the catalyst have smooth walls and uniform di-ameter distribution.