A new security architecture for SIP based P2P computer networks

Many applications are transferred from C/S (Client/Server) mode to P2P (Peer-to-Peer) mode such as VoIP (Voice over IP). This paper presents a new security architecture, i.e. a trustworthy authentication algorithm of peers, for Session Initialize Protocol (SIP) based P2P computer networks. A mechanism for node authentication using a cryptographic primitive called one-way accumulator is proposed to secure the P2P SIP computer networks. It leverages the distributed nature of P2P to allow for distributed resource discovery and rendezvous in a SIP network, thus eliminating (or at least reducing) the need for centralized servers. The distributed node authentication algorithm is established for the P2P SIP computer networks. The corresponding protocol has been implemented in our P2P SIP experiment platform successfully. The performance study has verified the proposed distributed node authentication algorithm for SIP based P2P computer networks

Volcanic deformation and degassing:the role of volatile exsolution and magma compressibility

Integrating multi-parameter observations of volcanic processes is crucial for volcano monitoring. Qualitative models demonstrate that combining observations of volcanic deformation, gas emissions, and other parameters enhances the detection of volcanic unrest and provide insights into the magma plumbing system. Despite the progress made in this field, quantitative models that link these observations are still lacking. Thermodynamic models have been used to constrain the characteristics of magma properties and its plumbing system. In this thesis, I develop models based on melt inclusion data and thermodynamics to reconstruct magma properties such as compressibility, and investigate how magmatic volatile content and magma storage conditions influence observations of volcanic deformation and SO2 degassing.By comparing mafic systems in arc and ocean island settings, I provide evidence for the lack of deformation observed during water-rich arc eruptions. In contrast, despite having low magmatic volatile content, ocean island eruptions have high SO2 emissions due to their high diffusivity, which results in co-eruptive degassing. By comparing model predictions and observations, I show that all magmatic systems experience a certain degree of outgassing prior to an eruption, consistent with current conceptual models of transcrustal magmatic systems. Additionally, integrating time series of deformation, degassing, and extrusion flux can reveal the evolution of magma properties. Using this framework, I provide evidence for the increase in bulk magma compressibility following the removal of the degassed magma during the 2004 eruption of Mount St. Helens. This study contributes to the better understanding of the effects of magmatic volatile content and pre-eruptive gas segregation on the physicochemical properties of magma, and provides a framework for modelling magma properties that can be applied to global volcano monitoring.</div

Phase diagram of asymmetric Fermi gas across Feshbach resonance

We study the phase diagram of the dilute two-component Fermi gas at zero temperature as a function of the polarization and coupling strength. We map out the detailed phase separations between superfluid and normal states near the Feshbach resonance. We show that there are three different coexistence of superfluid and normal phases corresponding to phase separated states between: (I) the partially polarized superfluid and the fully polarized normal phases, (II) the unpolarized superfluid and the fully polarized normal phases and (III) the unpolarized superfluid and the partially polarized normal phases from strong-coupling BEC side to weak-coupling BCS side. For pairing between two species, we found this phase separation regime gets wider and moves toward the BEC side for the majority species are heavier but shifts to BCS side and becomes narrow if they are lighter.Comment: 4 pages, 3 figures. Submitted to LT25 on June 200

Further investigation of a finite difference procedure for analyzing the transonic flow about harmonically oscillating airfoils and wings

Analytical and empirical studies of a finite difference method for the solution of the transonic flow about harmonically oscillating wings and airfoils are presented. The procedure is based on separating the velocity potential into steady and unsteady parts and linearizing the resulting unsteady equations for small disturbances. The steady velocity potential is obtained first from the well-known nonlinear equation for steady transonic flow. The unsteady velocity potential is then obtained from a linear differential equation in complex form with spatially varying coefficients. Since sinusoidal motion is assumed, the unsteady equation is independent of time. An out-of-core direct solution procedure was developed and applied to two-dimensional sections. Results are presented for a section of vanishing thickness in subsonic flow and an NACA 64A006 airfoil in supersonic flow. Good correlation is obtained in the first case at values of Mach number and reduced frequency of direct interest in flutter analyses. Reasonable results are obtained in the second case. Comparisons of two-dimensional finite difference solutions with exact analytic solutions indicate that the accuracy of the difference solution is dependent on the boundary conditions used on the outer boundaries. Homogeneous boundary conditions on the mesh edges that yield complex eigenvalues give the most accurate finite difference solutions. The plane outgoing wave boundary conditions meet these requirements