Capture of suspended particles by cylindrical collectors is an important mechanism in many aquatic processes, such as larval settlement, suspension feeding, and vegetative filtration. In these processes, the collector Reynolds number (Re c ), based on the collector diameter, ranges from well below 1 to 1,000. No analytical solutions exist to describe capture over most of this range. Capture is typically described by the efficiency, , defined as the ratio of the upstream span of particles that are captured on the collector to the collector diameter. Here, laboratory experiments are used to measure capture efficiency of a single cylinder as a function of Re c and particle ratio, R, which is the ratio of particle diameter to collector diameter. Re c is varied from 50 to 500 and three values of R are used: 0.03, 0.015, and 0.008. The selected particles have a specific gravity of 1.03. For smooth cylinders, capture increases with both Re c and R but is more strongly dependent on R. This result indicates that, in aquatic systems, where flow velocity and suspended particle type and size are fixed, higher capture efficiency will occur on the smallest collectors (those with largest R). Furthermore, we examine a similar experiment in which particles are collected by branched structures. We show that capture to individual cylindrical branches within a compound structure can be predicted by single-cylinder efficiencies. Finally, capture was increased when roughness elements were added to the collectors.
Modules attached to circuit cards by peripheral J- and gullwing leads were studied for their behavior under flexure. Three aspects of mechanical behavior were focused upon: the stiffness of the system, the forces arising in the leads, and the fatigue strength of the latter. The effective stiffness of a module-reinforced circuit card was measured experimentally in several configurations (load on card and load-on-module, double-sided and stacked). The leaded attachments were in two parallel rows. Analytical modeling of these tests were performed considering the leads as a continuous elastic foundation connecting the module and the card; test results were corroborated. Experiments were also conducted to establish the elastic and elastoplastic range of lead stiffness in three perpendicular directions: in two shearing planes and axially. The latter was the stiffest and most significant direction, motivating much of the present analysis. For lead force, the analytical procedure yielded values which were confirmed by finite element computation methods described previously by Engel (1990). Fatigue tests were performed on both J- and gullwing leads. Solder joints failed in the former, while lead failures occurred in the latter.
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