Browsing by Author "Wu, Jun"

Now showing 1 - 5 of 5
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    Machine learning and multi-dimension features based adaptive intrusion detection in ICN
    (IEEE, 2020-07-27) Li, Zhihao; Wu, Jun; Mumtaz, Shahid; Taha, A-E M.; Al-Rubaye, Saba; Tsourdos, Antonios
    As a new network architecture, Information-Centric Networks (ICN) has great advantages in content distribution and can better meet our needs. But it faced with many threats unavoidably. There are four types of attack in ICN: naming related attacks, routing related attacks, caching related attacks and miscellaneous attacks. These attacks will undermine the availability of ICN, the confidentiality and privacy of data. In addition, routers store a large amount of content for the users' request, and it is necessary to protect these intermediate nodes. Since the styles of content stored in nodes are not the same, using a unified set of intrusion detection rules simply will cause a large number of false positives and false negatives. Therefore, every node should perform intrusion detection according to its own characteristics. In this paper, we propose an intrusion detection mechanism to alert for abnormal packets. We introduce a extensive solution using machine learning for attacks in ICN. Moreover, the nodes in this scheme can adapt to the external environment and intelligently detect packets. Simulation on the machine learning algorithm involved prove that the algorithm is effective and suitable for network packets.
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    Nutrient metabolism, mass balance, and microbial structure community in a novel denitrifying phosphorus removal system based on the utilizing rules of acetate and propionate
    (Elsevier, 2020-05-18) Zhang, Miao; Zhu, Chenjie; Pan, Ting; Fan, Yajun; Soares, Ana; Wu, Jun; He, Chengda
    The effect of acetate (HAc) and propionate (HPr) on denitrifying phosphorus removal (DPR) was evaluated in a novel two-sludge A2/O - MBBR (anaerobic/anoxic/oxic - moving bed biofilm reactor) system. Results showed that it was the carbon source transformation and utilization especially the composition of poly-β-hydroxyalkanoates (PHA) (mainly poly-β-hydroxybutyrate (PHB) and poly-bhydroxyvalerate (PHV)) decided DPR performance, where the co-exist of HAc and HPr promoted the optimal nitrogen (85.77%) and phosphorus (91.37%) removals. It facilitated the balance of PHB and PHV and removing 1 mg NO3− (PO43−) consumed 3.04–4.25 (6.84–9.82) mgPHA, where approximately 40–45% carbon source was saved. Mass balance revealed the main metabolic pathways of carbon (MAn,C (consumed amount in anaerobic stage) and MA-O,C (consumed amount in anoxic and oxic stages): 66.38–76.19%), nitrogen (MDPR,N (consumed amount in DPR): 57.01–65.75%), and phosphorus (MWS,P (discharged amount in waste sludge): 81.05–85.82%). Furthermore, the relative abundance and microbial distribution were assessed to elucidate DPR mechanism (e.g. Accumulibacter, Acinetobacter, Dechloromonas, Competibacter, and Defluviicoccus) in the A2/O reactor and nitrification performance (e.g. Nitrosomonas, Nitrosomonadaceae and Nitrospira) in the MBBR. Carbon source was demonstrated as the key point to stimulate the biodiversity and bioactivity related to DPR potential, and the operational strategy of carbon source addition was proposed based on the utilizing rules of HAc and HPr.
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    Optimal Controller and Filter Realisations using Finite-precision, Floating- point Arithmetic.
    (Taylor & Francis, 2005-06-01T00:00:00Z) Whidborne, James F.; Gu, Da-Wei; Wu, Jun; Chen, Sheng
    The problem of reducing the fragility of digital controllers and filters implemented using finite-precision, floating-point arithmetic is considered. Floating-point arithmetic parameter uncertainty is multiplicative, unlike parameter uncertainty resulting from fixed-point arithmetic. Based on first- order eigenvalue sensitivity analysis, an upper bound on the eigenvalue perturbations is derived. Consequently, open-loop and closed-loop eigenvalue sensitivity measures are proposed. These measures are dependent upon the filter/ controller realization. Problems of obtaining the optimal realization with respect to both the open-loop and the closed-loop eigenvalue sensitivity measures are posed. The problem for the open-loop case is completely solved. Solutions for the closed-loop case are obtained using non-linear programming. The problems are illustrated with a numerical example.
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    Roles of nitrate recycling ratio in the A2/O-MBBR denitrifying phosphorus removal system for high-efficient wastewater treatment: Performance comparison, nutrient mechanism and potential evaluation
    (Elsevier, 2020-06-06) Zhang, Miao; Song, Tianxin; Zhu, Chenjie; Fan, Yajun; Soares, Ana; Gu, Xiaodan; Wu, Jun
    The long-term effect of nitrate recycling ratios (R = 100%–500%) on the denitrifying phosphorus removal (DPR) characteristics was studied in a novel two-sludge system, which coupled Anaerobic Anoxic Oxic (A2/O) with Moving Bed Biofilm Reactor (MBBR) for simultaneous nitrogen (N) and phosphorus (P) removals. During the 220 days’ operation, effluent COD (30.87–45.15 mg/L) can meet the discharge standard completely, but N and P removals were significantly affected by the R-value, including CODintra removal efficiency (CODintra-Re: 56.09–85.98%), TN removal (TN-Re: 52.06–80.50%), anaerobic PO43− release (PO43--An: 10.66–29.02 mg/L) and oxic PO43− absorption (PO43--O: 2.22–6.26 mg/L). Meanwhile, N and P displayed close correlation with the ΔPO43−/ΔNO3- ratio of 4.20–4.41 at R = 300%–400%, resulting in the high-efficient anoxic poly-β-hydroxyalkanoates (PHA) utilization (ΔPHAA: 64.88 mgCOD/gVSS). Based on the stoichiometry methodology, at R of 300%–400%, the percentages of phosphorus accumulation organisms (PAOs) and glycogen accumulating organisms (GAOs) contributed to ΔPHAAn (ΔGlyAn) were 71.7%, 28.3% (61.3%, 38.7%) in the anaerobic stage, respectively, while N denitrification rate (NDRA: 3.91–3.93 mg N/(gVSS·h)) and P uptake rate (PURA: 3.76–3.90 mg P/(gVSS·h)) reached the peak, suggesting superior DPR performance with higher contribution of denitrifying PAOs (DPAOs) (70%) than denitrifying GAOs (DGAOs) (30%) in the anoxic stage. Microbial community analysis showed that Accumulibacter (27.66–30.01%) was more enriched than Competibacter (13.41–14.34%) and was responsible for the improved C, N, P removals and DPR characteristics. For optimizing operation, the combined effect of nitrate recycling ratio with other process parameters especially economic evaluation should be considered
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    A Unified Closed-Loop Stability Measure for Finite-Precision Digital Controller Realizations Implemented in Different Representation Schemes.
    (IEEE Institute of Electrical and Electronics, 2003-05-01T00:00:00Z) Wu, Jun; Chen, Sheng; Whidborne, James F.; Chu, Jian
    A computationally tractable unified finite word length closed-loop stability measure is derived which is applicable to fixed-point, floating-point and block- floating-point representation schemes. Both the dynamic range and precision of an arithmetic scheme are considered in this new unified measure. For each arithmetic scheme, the optimal controller realization problem is defined and a numerical optimization approach is adopted to solve it. Numerical examples are used to illustrate the design procedure and to compare the optimal controller realizations in different representation schemes.