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Real time data collection in traffic engineering is crucial for better traffic corridor control and management. In the literature, many data collection methods have been used such as; magnetic loops, road tube counters, piezo sensors, radars, Bluetooth etc. to estimate the link occupancy, average speed or density of a corridor. More recently, Floating Car Data (FCD) has become another important traffic data source and has an increasing usage due to its lower cost and higher coverage despite its reliability problems. FCD obtained from GPS equipped vehicles moving in the traffic can provide speed or travel speed data for many segments for even 1-min intervals in real-time. Though not totally diverse providing more than one of the traffic flow parameters, measuring the effectiveness of this extensive data source in detecting some critical urban traffic states is the ultimate goal of this study. As a case study, 1-min interval FCD for an urban arterial in Ankara has been collected during the morning peak hour for 2 months. Average speed values were transformed into a qualitative 4-scale state parameter based on the Level of Service (LOS) definitions for urban roads. Pattern searches over consecutive segment states using different search length (i.e. 2 segments, 3 segments, etc.) showed that FCD is capable to detect recurrent congestion or bottleneck locations, and even have an idea about the length of queue formed before the bottlenecks.

The Poisson–Boltzmann (PB) equation has been extensively used to analyze the energetics and structure of proteins and other significant biomolecules immersed in electrolyte media. A new highly efficient approach for solving PB‐type equations that allows for the modeling of many‐atoms structures such as encountered in cell biology, virology, and nanotechnology is presented. We accomplish these efficiencies by reformulating the elliptic PB equation as the long‐time solution of an advection‐diffusion equation. An efficient modified, memory optimized, alternating direction implicit scheme is used to integrate the reformulated PB equation. Our approach is demonstrated on protein composites (a polio viruscapsid protomer and a pentamer). The approach has great potential for the analysis of supramillion atoms immersed in a host electrolyte. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1068–1074, 2004

A study of body waves in fractured porous media saturated by two fluids is presented. We show the existence of four compressional and one rotational waves. The first and third compressional waves are analogous to the fast and slow compressional waves in Biot's theory. The second compressional wave arises because of fractures, whereas the fourth compressional wave is associated with the pressure difference between the fluid phases in the porous blocks. The effects of fractures on the phase velocity and attenuation coefficient of body waves are numerically investigated for a fractured sandstone saturated by air and water phases. All compressional waves except the first compressional wave are diffusive-type waves, i.e., highly attenuated and do not exist at low frequencies.

A theory of wave propagation in fractured porous media is presented based on the double-porosity concept. The macroscopic constitutive relations and mass and momentum balance equations are obtained by volume averaging the microscale balance and constitutive equations and assuming small deformations. In microscale, the grains are assumed to be linearly elastic and the fluids are Newtonian. Momentum transfer terms are expressed in terms of intrinsic and relative permeabilities assuming the validity of Darcy's law in fractured porous media. The macroscopic constitutive relations of elastic porous media saturated by one or two fluids and saturated fractured porous media can be obtained from the constitutive relations developed in the paper. In the simplest case, the final set of governing equations reduce to Biot's equations containing the same parameters as of Biot and Willis.

In one-dimensional (1D) early diagenetic models, bioirrigation is typically represented by a nonlocal mass transfer or bioirrigation coefficient, a. Usually, all pore water species are assigned the same a. Here, we show that this assumption can lead to significant errors in estimates of bioirrigation intensities. Using a simplified early diagenetic reaction network, we compute the 3D concentration fields of major pore water species around a vertical burrow, as well as the solute fluxes across the burrow wall. From these results, corresponding 1D vertical a profiles are derived. The a profiles show pronounced differences from one solute to another. Dissolved 02 systematically exhibits the highest a values, while fast oxygenation kinetics near the burrow wall result in near-zero a values for aqueous Fe2+ For nitrate, use of a species-avenged a profile may even lead to an erroneous prediction of the direction of the irrigation flux across the water-sediment interface. The large differences in a profiles reflect the variable effects of biogeochemical processes on pore water concentration fields of reactive solutes near the burrow wall. Even for inert solutes, however, determination of a can be ambiguous. Transient simulations mimicking the intrusion into the sediment of an inert tracer during an incubation experiment yield apparent mixing intensities that depend on the incubation time. [ABSTRACT FROM AUTHOR]