844 research outputs found
Improved Bounds for Randomly Colouring Simple Hypergraphs
Full text linkWe study the problem of sampling almost uniform proper q-colourings in k-uniform simple hypergraphs with maximum degree Δ. For any δ > 0, if k ≥ 20(1+δ)/δ and q ≥ 100Δ^({2+δ}/{k-4/δ-4}), the running time of our algorithm is Õ(poly(Δ k)⋅ n^1.01), where n is the number of vertices. Our result requires fewer colours than previous results for general hypergraphs (Jain, Pham, and Vuong, 2021; He, Sun, and Wu, 2021), and does not require Ω(log n) colours unlike the work of Frieze and Anastos (2017)
Reclamation of tidal flats within tidal basins alters centennial morphodynamic adaptation to sea‐level rise
No full textReclamation of low-lying tidal flats and floodplains adjacent to present shorelines has been implemented worldwide for both coastal defense and development. While it is technically feasible to monitor the short-term impact of tidal flat embankments, it is challenging to identify long-term and cumulative morphodynamic impact, particularly considering centennial sea-level rise (SLR). In this study, we construct a process-based hydro-morphodynamic model for a schematized tidal basin and examine its morphodynamic evolution under the combined influence of SLR and tidal flat embankments. We see that rising sea levels lead to inundation of low-lying floodplains just above high water, creating new intertidal flats that mitigate the drowning impact of SLR. This mitigation effect is lost if the low-lying floodplains and tidal flats are reclaimed, preventing any shoreline migration under SLR. Removing a large portion of intertidal flats within the tidal basin induces significant changes in basin hypsometry and potentially, a reversal of flood/ebb dominance. The resulting hydro-morphodynamic impact of large-scale tidal flat embankment is more significant than SLR at a centennial time scale. This suggests a need for much greater management awareness regarding the cumulative impact of human activities. These findings imply that allowing lateral shoreline migration under SLR sustains tidal basin's inherent morphodynamic buffering capacity, whereas reclaiming tidal flats significantly alters hydro-morphodynamic adaptation at the decadal to centennial time scales. It highlights the importance of conserving low-lying floodplains and tidal flats in tide-dominated systems to counteract the drowning impact of SLR.</p
AN E-BROKERAGE APPROACH BASED ON MULTI-AGENT TECHNOLOGY
Full text linkIn this paper the author shows the importance of multi-agent system in the e-commerce domain, specially for brokerage. He also propose an agent-based architecture for brokerage and a structure for the intelligent broker. The structure may be seen like a multi-agent system, having intelligent agents that are doing specific tasks for brokerage activity. In the end, conclusions reveal some aspects that may be start points for future researches.E-commerce, intelligent agent, brokerage, multi-agent systems.
Distributed Detection of Network Intrusions Based on a Parametric Model
No full textWith the increasing requirements of fast response and privacy protection, how to detect network intrusions in a distributed architecture becomes a hot research area in the development of modern information security systems. However, it is a challenge to build such a system, given the difficulties brought by the mixed-attribute property of network connection data and the constraints on network communication. In this paper, we present a framework for distributed detection of network intrusions based on a parametric model. The parametric model can explicitly reflect the distributions of different intrusion types and handle the mixed-attribute data naturally. Based on the model, we can generate an accurate global intrusion detector with a very low cost of communication among the distributed detection sites, and no sharing of original network data is needed. Experimental results demonstrate the advantages of the proposed framework in the distributed intrusion detection application.Yan-guo Wang, Xi Li, and Weiming Huhttp://smc.elite.sg/2008
Study on route division for ship energy efficiency optimization based on big environment data
No full textIn the case of the global energy crisis and the higher sound of energy saving and emission reduction, how to take effective management measures of ship energy efficiency to achieve the goal of energy saving and emission reduction, put forward a new challenge for the development of shipping technology. The application of big data technology provides a new idea for the research of ship energy efficiency optimization management. The energy efficiency management level of the operating ship can be improved by the analysis and mining of the big data. In this paper, a big data analysis platform for ship energy efficiency management based on the widely used Hadoop platform architecture is designed. Afterward, due to the huge amount of involved data on the energy efficiency management which has exceeded the processing ability of traditional solutions, the big data analysis method is used to achieve the route division according to environmental factors, thus to lay the foundation for speed optimization in different segments of a route. Finally, a simple decision-making method of optimal engine speed based on the result of route division is proposed, which could improve ship energy efficiency and hence reduce CO2 emission.Accepted Author ManuscriptTransport Engineering and Logistic
Rapid Mixing of the Flip Chain over Non-Crossing Spanning Trees
Full text linkWe show that the flip chain for non-crossing spanning trees of n+1 points in convex position mixes in time O(n⁸log n). We use connections between Fuss-Catalan structures to construct a comparison argument with a chain similar to Wilson’s lattice path chain (Wilson 2004)
Template-assembled peptide models of the N-peptide helix bundle from HIV-1 Gp41
No full textThe HIV-1 pandemic is one of the most serious health problems facing the world today. Infection of target cells by HIV-1 is initiated by fusion of viral and cell membranes, which is mediated by the viral glycoproteins, gp120 and gp41. After initial cell binding by gp120, the folding of gp41 to form a stable six-helix bundle structure is directly associated with membrane fusion. This helix bundle is composed of an α-helical trimer of gp41 N-helices, with three copies of the α-helical gp41 C-peptides folded onto it in an antiparallel orientation. Peptides that interfere with the formation of this six-helix bundle structure by targeting either the N-helix or the C-helix are believed to be able to block the cell fusion process and therefore prevent HIV-1 infection.
In this study, we successfully synthesized three-helix peptide structures of gp41 as models of the internal N-helix bundle, by assembling three copies of N-peptides onto three-fold symmetric templates. The templates were derived from cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid (Kemp's Triacid, KTA) or tris(2-aminoethyl)amine (TREN), which represent choices of rigid and flexible molecules, respectively, for organization of the folding of the N-peptide three-helix bundle.
Biophysical analysis of the four synthetic model structures, KTA-3N29, TREN-3N29, KTA-3N29b and TREN-3K-N29b, demonstrated that, at neutral pH, they all exist as monomers with high helix contents. Binding isotherms, measured by circular dichroism spectropolarimetry in the presence of physiological salt, indicated that KTA-3N29b binds three copies of the C-peptide native sequence, with a KD of about 260 nM, while TREN-3K-N29b binds to C-peptide with a KD in the low-micromolar range. Within the scope of this investigation, KTA-Br, the relatively more rigid template derived from KTA, was the best design for a template for the N-peptide bundle, since it generated the most helical, and most stable three-helix bundle structure with the highest binding affinity for C-peptides. These features of KTA-3N29b demonstrate that this templated three-helix bundle serves as a functional model for the native N-peptide structure that will allow detailed studies of the folding and thermodynamic stability of the gp41 six-helix bundle, and may aid the future development of potent HIV-1 fusion inhibitors and immunogens.Ph.D.Includes bibliographical references
- …
