Cohesive fracture model for functionally graded fiber reinforced concrete

A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.     

A generic algorithm for optimization of CFSTRs in series with any biokinetic equation

A simple generic code for optimization of CFSTRs in series with any biokinetic equation (structured, unstructured, segregated or distributed) has been developed. The program accepts biokinetic equations without any preliminary mathematical manipulation, does necessary material balances, solves material balance equations and optimizes the system under a given objective function. The program was tested with four different optimization problems (different biokinetics of unstructured, segregated and a structured model) and the results were compared to published data. In all cases, good agreement was found. Finally, the model has been applied to multiple CFSTRs with a cybernetic biokinetic model, and the effect of model parameters on the optimum total residence time is demonstrated.     

Case Study of Urban Concrete Pavement Reconstruction on Interstate 10

Many urban concrete pavements in California need to be reconstructed, as they have exceeded their design lives and require frequent maintenance and repair. Information is needed to determine which methodologies for pavement design, materials selection, traffic management, and reconstruction strategies are most suitable to achieve the objectives of California Department of Transportation’s (Caltrans) long-life pavement rehabilitation strategies (LLPRS) program. To develop construction productivity information for several construction windows, a case study was performed on a Caltrans concrete rehabilitation demonstration project near Los Angeles on Interstate-10, where 20 lane-km was successfully rebuilt using fast setting hydraulic cement concrete (FSHCC) with one weekend closure for 2.8 lane-km and repeated 7- and 10-h nighttime closures for the remaining distance. The concrete delivery and discharge controlled the overall progress. In terms of the number of slabs replaced per hour, the 55-h weekend closure was 54% faster than the average nighttime closure. An excellent traffic management strategy helped to reduce the volume of traffic during the weekend closure and minimize the traffic delay through the construction zone.     

The effect of advice message location on user performance

In 1993, a study began with a large commercial oil and gas software interpretation system to determine the feasibility of a general taxonomy of on-line help content and a corresponding taxonomy of human interface access methods to this content. The preliminary findings from this work were encouraging and indicate that a taxonomic approach makes it easy both for help providers to understand what information they need to supply, and for help users to find the help they need quickly. Part of this taxonomy of help content includes application messaging. Existing studies of on-line help messaging indicate that both user-initiated or system-initiated advice messaging can improve user efficiency by prompting users with information about what something on the interface is, what it does, or what to do once it has been activated. This study examines the placement of on-line help messages in a multiwindow software application on user performance. Subjects were automatically timed as they performed two sets of tasks: one where help messages always appeared at the bottom of an application's main window and one where help messages appeared at the bottom of the current window in focus     

Modeling and simulation, and their validation of three-phasetransformers with three legs under DC bias

This paper proposes a new model for three-phase transformers with three legs with and without task under DC bias based on electric and magnetic circuit theory. For the calculation of the nonsinusoidal no-load currents, a combination of time and frequency domains is used. The analysis shows that (1) asymmetric three-phase transformers with three legs generate magnetizing currents with triplen harmonics not being of the zero-sequence type. (2) The wave shapes of the three magnetizing currents of (asymmetric) transformers are dependent on the phase sequence. (3) The magnetic history of transformer magnetization-due to residual magnetization and hysteresis of the tank-cannot be ignored if a DC bias is present and the magnetic influence of the tank is relatively strong, e.g., for oil-cooled transformers. (4) Symmetric three-phase transformers with three legs generate no-load currents without triplen harmonics. (5) The effects of DC bias currents (e.g., reactive power demand, harmonic distortion) can be suppressed employing symmetric three-phase transformers with three legs including tank. Measurements corroborate computational results; thus this nonlinear model is valid and accurate     

Physics of cosmic radiation fields.

This paper glances at the knowledge of composition and energy spectra of galactic cosmic rays and briefly discusses the mechanism of solar modulation and of shielding against these particles by the earth's magnetic field. A short review of the properties of solar particle events is given, in which particles emitted from the sun enter the atmosphere. Particle production in the earth's atmosphere in hadronic and electromagnetic cascades is described and the altitude variations of the different particle components are investigated. Typical energy spectra in the atmosphere are presented for some types of particles.     

Sensitivity of Electrical Appliances to Harmonics and Fractional Harmonics of the Power System's Voltage. Part II: Television Sets, Induction Watthour Meters and Universal Machines

The sensitivity of television sets, induction watthour meters and universal motors to harmonics and fractional harmonics, as they occur in home appliances, is derived analytically and experimentally. This study shows that television sets are very sensitive to fractional harmonics. Calculations and measurements performed with single-phase watthour meters show that the harmonic torques within the aluminum disk are always positive and accelerate the disk. Universal machines are not as sensitive to voltage harmonics as compared with induction machines. The work described has been supported by the U.S. Department of Energy.     

Benchmark studies of induced radioactivity produced in LHC materials, Part I: Specific activities

Samples of materials which will be used in the LHC machine for shielding and construction components were irradiated in the stray radiation field of the CERN-EU high-energy reference field facility. After irradiation, the specific activities induced in the various samples were analysed with a high-precision gamma spectrometer at various cooling times, allowing identification of isotopes with a wide range of half-lives. Furthermore, the irradiation experiment was simulated in detail with the FLUKA Monte Carlo code. A comparison of measured and calculated specific activities shows good agreement, supporting the use of FLUKA for estimating the level of induced activity in the LHC.