Application of artificial neural network on vibration test data for damage identification in bridge girder

Structures are exposed to damage during their service life which can severely affect their safety and functionality. Thus, it is important to monitor structures for the occurrence, location and extent of damage. Artificial neural networks (ANNs) as a numerical technique have been applied increasingly for damage identification with varied success. ANNs are inspired by human biological neurons and have been used to model some specific problems in many areas of engineering and science to achieve reasonable results. ANNs have the ability to learn from examples and then adapt to changing situations when sufficient input-output data are available. This paper presents the application of ANNs for detection of damage in a steel girder bridge using natural frequencies as dynamic parameters. Dynamic parameters are easy to implement for damage assessment and can be directly linked to the topology of structure. In this study, the required data for the ANNs in the form of natural frequencies will be obtained from experimental modal analysis. This paper also highlights the concept of ANNs followed by the detail presentation of the experimental modal analysis for natural frequencies extraction

Multi-phase-field analysis of short-range forces between diffuse interfaces

We characterize both analytically and numerically short-range forces between spatially diffuse interfaces in multi-phase-field models of polycrystalline materials. During late-stage solidification, crystal-melt interfaces may attract or repel each other depending on the degree of misorientation between impinging grains, temperature, composition, and stress. To characterize this interaction, we map the multi-phase-field equations for stationary interfaces to a multi-dimensional classical mechanical scattering problem. From the solution of this problem, we derive asymptotic forms for short-range forces between interfaces for distances larger than the interface thickness. The results show that forces are always attractive for traditional models where each phase-field represents the phase fraction of a given grain. Those predictions are validated by numerical computations of forces for all distances. Based on insights from the scattering problem, we propose a new multi-phase-field formulation that can describe both attractive and repulsive forces in real systems. This model is then used to investigate the influence of solute addition and a uniaxial stress perpendicular to the interface. Solute addition leads to bistability of different interfacial equilibrium states, with the temperature range of bistability increasing with strength of partitioning. Stress in turn, is shown to be equivalent to a temperature change through a standard Clausius-Clapeyron relation. The implications of those results for understanding grain boundary premelting are discussed.Comment: 24 pages, 28 figure

Exploiting the Synergy Between Gossiping and Structured Overlays

In this position paper we argue for exploiting the synergy between gossip-based algorithms and structured overlay networks (SON). These two strands of research have both aimed at building fault-tolerant, dynamic, self-managing, and large-scale distributed systems. Despite the common goals, the two areas have, however, been relatively isolated. We focus on three problem domains where there is an untapped potential of using gossiping combined with SONs. We argue for applying gossip-based membership for ring-based SONs---such as Chord and Bamboo---to make them handle partition mergers and loopy networks. We argue that small world SONs---such as Accordion and Mercury---are specifically well-suited for gossip-based membership management. The benefits would be better graph-theoretic properties. Finally, we argue that gossip-based algorithms could use the overlay constructed by SONs. For example, many unreliable broadcast algorithms for SONs could be augmented with anti-entropy protocols. Similarly, gossip-based aggregation could be used in SONs for network size estimation and load-balancing purposes

Nuclear Isospin Diffusivity

The isospin diffusion and other irreversible phenomena are discussed for a two-component nuclear Fermi system. The set of Boltzmann transport equations, such as employed for reactions, are linearized, for weak deviations of a system from uniformity, in order to arrive at nonreversible fluxes linear in the nonuniformities. Besides the diffusion driven by a concentration gradient, also the diffusion driven by temperature and pressure gradients is considered. Diffusivity, conductivity, heat conduction and shear viscosity coefficients are formally expressed in terms of the responses of distribution functions to the nonuniformities. The linearized Boltzmann-equation set is solved, under the approximation of constant form-factors in the distribution-function responses, to find concrete expressions for the transport coefficients in terms of weighted collision integrals. The coefficients are calculated numerically for nuclear matter, using experimental nucleon-nucleon cross sections. The isospin diffusivity is inversely proportional to the neutron-proton cross section and is also sensitive to the symmetry energy. At low temperatures in symmetric matter, the diffusivity is directly proportional to the symmetry energy.Comment: 35 pages, 1 table, 5 figures, accepted by PRC, (v3) changes in response to the referee's comments, discussion for isospin diffusion process in heavy-ion reactions, fig. 5 shows results from a two different isospin depndent uclear equation of state, and a new reference adde

A Review: Study on Spent Garnet as Construction Material

Numerous environmental problems are mitigated by natural resource depletion, with yearly global use of nearly 25 billion tonnes, including aggregates. Fast industrial growth has witnessed the ever-increasing exploitation of sand from rivers for various construction resolves, which caused an over-exploitation of rivers’ beds and disturbed the eco-system. This problem is also related to the amount of waste produced each year. The volume of waste is estimated to rise, reducing available space and causing pollution. Many studies have discovered inventions and ideas to deal with this situation. Some researchers use the spent garnet in a concrete mix as a partial fine aggregate replacement. The alternative in a concrete mix depends on the properties of the spent garnet that is used and its appropriateness. In this paper, a critical review of spent garnet were discussed in detail

A Review: Study on Spent Garnet as Construction Material

Numerous environmental problems are mitigated by natural resource depletion, with yearly global use of nearly 25 billion tonnes, including aggregates. Fast industrial growth has witnessed the ever-increasing exploitation of sand from rivers for various construction resolves, which caused an over-exploitation of rivers’ beds and disturbed the eco-system. This problem is also related to the amount of waste produced each year. The volume of waste is estimated to rise, reducing available space and causing pollution. Many studies have discovered inventions and ideas to deal with this situation. Some researchers use the spent garnet in a concrete mix as a partial fine aggregate replacement. The alternative in a concrete mix depends on the properties of the spent garnet that is used and its appropriateness. In this paper, a critical review of spent garnet were discussed in detail

Electromagnetic force density in dissipative isotropic media

We derive an expression for the macroscopic force density that a narrow-band electromagnetic field imposes on a dissipative isotropic medium. The result is obtained by averaging the microscopic form for Lorentz force density. The derived expression allows us to calculate realistic electromagnetic forces in a wide range of materials that are described by complex-valued electric permittivity and magnetic permeability. The three-dimensional energy-momentum tensor in our expression reduces for lossless media to the so-called Helmholtz tensor that has not been contradicted in any experiment so far. The momentum density of the field does not coincide with any well-known expression, but for non-magnetic materials it matches the Abraham expression

Acute myocardial infarction in Zimbabwe: the changing scene of coronary artery disease

From 1988 to 1993 (six years), 127 suspected cases of acute myocardial infarction (AMI) were admitted to the Parirenyatwa Hospital coronary care unit. AMI was confirmed in 76 cases, 37 were Black, 27 White, six Indian and six Coloured. For Blacks the male to female ratio was 5:1. The clinical and laboratory features and complications of AMI were similar in all ethnic groups. Compared to other groups, Blacks presented to hospital late, an observation which has important implications for thrombolytic therapy. With the increasing number of cases of AMI now being seen among Black Zimbabweans, the time has come for the evaluation of the changing risk factor profile and the initiation of education and intervention programmes which could contain this rise before it spirals into a major health problem