Stochastic Analysis of a Single-Degree-of-Freedom Nonlinear Experimental Moored System Using an Independent-Flow-Field Model

Stochastic characteristics of the surge response of a nonlinear single-degree-of-freedom moored structure subjected to random wave excitations are examined in this paper. Sources of nonlinearity of the system include a complex geometric configuration and wave-induced quadratic drag. A Morison-type model with an independent-flow-field formulation and a three-term-polynomial approximation of the nonlinear restoring force is employed for its proven excellent prediction capability for the experimental results investigated. Wave excitations considered in this study include nearly periodic waves, which take into account the presence of tank noise, noisy periodic waves that have predominant periodic components with designed additive random perturbations, and narrow-band random waves. A unified wave excitation model is used to describe all the wave conditions. A modulating factor governing the degree of randomness in the wave excitations is introduced. The corresponding Fokker–Planck formulation is applied and numerically solved for the response probability density functions (PDFs). Experimental results and simulations are compared in detail via the PDFs in phase space. The PDFs portray coexisting multiple response attractors and indicate their relative strengths, and experimental response behaviors, including transitions and interactions, are accordingly interpreted from the ensemble perspective. Using time-averaged probability density functions as an invariant measure, probability distributions of large excursions in experimental and simulated responses to various random wave excitations are demonstrated and compared. Asymptotic long-term behaviors of the experimental responses are then inferred.     

Hydriding properties of Mg–xNi alloys with different microstructures

The hydriding properties of Mg–xNi (x = 13.5, 23.5 and 33.5 wt%) alloys with different microstructures produced by various processing routes were evaluated in this study. The hydrogen storage capacity and kinetics of hydriding of Mg–xNi alloys were strongly dependent on their microstructures. The capacity and kinetics of hydriding were larger and faster when the average size of the hydriding phase was smaller and the volume fraction of the phase boundary was larger.     

A secure framework of the surveillance video network integrating heterogeneous video formats and protocols

Recently, IT technologies are becoming focused on different traditional industries. The large scaled intelligent video surveillance system is one of them and it integrates a large number of digitalized CCTV [1] devices through the Web. However, existing video devices have been deployed for many years by different vendors as different models with different specifications. To integrate these heterogeneous devices, the centralized management server (CMS) and its clients need a specialized architecture to deal with different types of media encodings and connection protocols etc. In particular, well-defined access control mechanism is required for a large scaled surveillance video network. In this paper, we designed and implemented a server that incorporates the architecture integrating and delivering multiple video streams from different types of video devices to multiple clients and securing the access to the video streams.     

Hierarchical Binary Search Tree for Packet Classification

In order to provide value-added services such as policy-based routing and the quality of services in next generation network, the Internet routers need to classify packets into flows for different treatments. Since packet classification should be performed in wire-speed for every packet incoming in several hundred gigabits per second, it becomes a major challenge in the Internet routers. In this letter, we propose a new packet classification scheme based on hierarchical binary search tree. The proposed scheme hierarchically connects binary search trees without empty internal nodes, and hence the proposed architecture significantly improves the search performance as well as greatly reduces the memory requirement compared with trie-based schemes.     

Prediction and experimental verification of damping in 3-D braided textile structural composites

The material damping characteristics of 3-D braided textile structural composites were investigated in this paper. A model for predicting damping in these materials was developed based upon the classical laminated plate theory. The model modified the existing models for predicting the static moduli of 3-D textile structural composites by using the elastic-viscoelastic correspondence principle. The basic engineering constants were replaced with their corresponding complex forms by applying the elastic-viscoelastic correspondence principle to them. In this study, the basic damping loss factors (i.e. η_L, η_T, η_LT and η_vLT) were obtaiend by a modified Hashin's theory, Rule-of-Mixture Laws, and an indirect method on the basis of empirical works. From complex numerical results, we concluded that axial damping, flexural damping, coupling damping, and in-plane shear damping coefficients were all functions of the yarn orientation angle and fiber volume fraction in 3-D braided textile structural composites. Experimental data supported theoretically predicted results.     

Performance and durability of sulfonated poly(arylene ether sulfone) membrane-based membrane electrode assemblies fabricated by decal method for polymer electrolyte fuel cells

The combination of Nafion-based electrode and hydrocarbon-based membrane is an ideal choice for researcher in making membrane electrode assemblies (MEAs) containing alternative membranes replacing Nafion for polymer electrolyte fuel cells (PEFCs) due to their intrinsic properties. This advantage, however, is limited by the incompatibility between the membrane and the electrode, which results in MEA performance decay and low durability. In this study, we propose fabrication of MEA made of sulfonated poly(aryl ether sulfone) (SPES) membrane and Nafion-based electrode using the decal process. The decal process was found to be very effective in forming good interface between SPES and the electrode, although hot pressing temperature was relatively low (140 °C). The SPES-MEA revealed comparable performance to conventional Nafion-MEA at high humidity, indicating negligible contact resistance in the SPES–electrode interface. Open circuit voltage (OCV) drop of SPES-MEA during OCV holding at 40% RH for 200 h was from 0.975 V to 0.8 V, implying slight chemical degradation of SPES leading to increased hydrogen crossover in the membrane. However, it seems that the interfacial damage between the SPES and Nafion electrode in the SPES-MEA is negligible during the OCV test. Nonetheless, further investigation is necessary to confirm the long-term stability of the SPES-MEA fabricated by the decal process under harsher conditions such as dry/wet and freeze/thaw cycling.     

A cell culture system for study of the development of Toxoplasma gondii bradyzoites

Toxoplasma gondii is a ubiquitous apicomplexan parasite and a major opportunistic pathogen under AIDS-induced conditions, where it causes encephalitis when the bradyzoite (cyst) stage is reactivated. A bradyzoite-specific Mab, 74.1.8, reacting with a 28 kDa antigen, was used to study bradyzoite development in vitro by immuno-electron microscopy and immunofluorescence in human fibroblasts infected with ME49 strain T. gondii. Bradyzoites were detected in tissue culture within 3 days of infection. Free floating cyst-like structures were also identified. Western blotting demonstrated the expression of bradyzoite antigens in these free-floating cysts as well as in the monolayer. Bradyzoite development was increased by using media adjusted to pH 6.8 or 8.2. The addition of gamma-interferon at day 3 of culture while decreasing the total number of cysts formed prevented tachyzoite overgrowth and enabled study of in vitro bradyzoites for up to 25 days. The addition of IL-6 increased the number of cysts released into the medium and increased the number of cysts formed at pH 7.2. Confirmation of bradyzoite development in vitro was provided by electron microscopy. It is possible that the induction of an acute phase response in the host cell may be important for bradyzoite differentiation. This system should allow further studies on the effect of various agents on the development of bradyzoites.