[1] Subsurface flow within a single riffle of a low-gradient gravel bed stream was modeled in three dimensions using MODFLOW, a finite difference groundwater flow model. Model simulations showed that exchange flows can only occur in this low-gradient, gaining stream because of a zone of alluvial sediment around the stream that has much higher permeability than the surrounding catchment (K = 10 ...

In this paper, the empirical equations that estimate hydraulic parameters for non-linear flow through coarse porous media are evaluated using a series of independent data collected in the laboratory. In this regard, three different relatively uniform soils ranging in size from 8.5 to 27.6 mm have been selected and three random samples drawn from each material. The physical characteristics such ...

Polycyclic aromatic hydrocarbon (PAH) contamination exists at numerous sites and poses a substantial risk to public health and the environment. Electrokinetic remediation technology has the potential to treat PAH-contaminated soils, but the effect of soil heterogeneities such as layers, lenses, and mixtures of different soils on the electrokinetic process has not been adequately studied. This s...

We studied relationships among branch hydraulic conductivity, xylem embolism, stomatal conductance (gs), foliar nitrogen (N) concentration and specific leaf area (SLA) of seven tree species growing at four temperate woodland sites spanning a 464-1350 mm rainfall gradient. Specifically, we examined the question: are gs and foliar N concentration coordinated with branch hydraulic conductivity and...

The relationships between hydraulic and photosynthetic properties in plants have been widely studied, but much less is known about how these properties are linked to water-source partitioning, the spatial and temporal separation of water sources in ecosystems. Plant water-source partitioning is often influenced by the proximity of groundwater from the natural surface. We studied the water acqui...

We discuss open loop control development and simulation results for a semiactive above-knee prosthesis. The control signal consists of two hydraulic valve settings. These valves control a rotary actuator that provides torque to the prosthetic knee. We develop open loop control using biogeography-based optimization (BBO), which is a recently developed evolutionary algorithm, and gradient descent...

The main purpose of this article is to study fabrication methods and applications of aligned carbon nanotube (CNT) membranes as a hydraulic microstructure in treatment processes. This paper emphasizes the use of CNTs as membrane in separation processes like water and wastewater treatment because of their exclusive advantages. Their most important characteristics are high mechanical strength aga...

where P represents the pressure gradient between the pulmonary artery and the pulmonary vein, F, the blood flow per unit time, and R. the vascular resistance. For a given pressure gradient and flow rate, R will be determined, among other things, by the physical dimensions of the chaniiels that the blood traverses. In a rigid hydraulic system this formula applies over a wide range of flow and pr...