Deformation of a pipeline element under cyclic loading by internal pressure

An experimental study of the strain of a rectilinear segment of a pipeline Du 200 made of steel 20 under cyclic loading by internal pressure was carry out. The tests were performed on a pneumohydraulic stand under conditions of flat stress, normal temperatures, and load cycle asymmetry with registration of circular and axial elastic-plastic strain. The aim of the work was to test an experimental technique for studying the effect of ratcheting (unilateral accumulation of plastic deformations) on real structural elements when changing the modes of cyclic loading. According to the results of the study, curves of cyclic deformation (ratcheting) of the pipe in the circular and axial direction on the basis 100 cycles were obtained.

Structures based on elliptical arcs in the problems of designing trajectories and creating mechanical systems

An experimental study of the strain of a rectilinear segment of a pipeline Du 200 made of steel 20 under cyclic loading by internal pressure was carry out. The tests were performed on a pneumohydraulic stand under conditions of flat stress, normal temperatures, and load cycle asymmetry with registration of circular and axial elastic-plastic strain. The aim of the work was to test an experimental technique for studying the effect of ratcheting (unilateral accumulation of plastic deformations) on real structural elements when changing the modes of cyclic loading. According to the results of the study, curves of cyclic deformation (ratcheting) of the pipe in the circular and axial direction on the basis 100 cycles were obtained.

A Geometric Extension of Schwarz’s Lemma and Applications

Let f be a holomorphic function of the unit disc , preserving the origin. According to Schwarz’s Lemma, |f'(0)| ≤ 1, provided that . We prove that this bound still holds, assuming only that f() does not contain any closed rectilinear segment [0, eiϕ], ϕ ∊ [0, zπ], i.e., does not contain any entire radius of the closed unit disc. Furthermore, we apply this result to the hyperbolic density and give a covering theorem.

Talus fabric, clast morphology, and botanical Indicators of Slope Processes on the Chaos Crags (California Cascades), U.S.A.

The Chaos Crags, a group of dacite domes in the Cascades Mtns (California), were affected by volcanic debris avalanches ca. 1675 A.D.; these left a sizable deposit and a scar on the north mountain flank, now covered by talus. This report examines the fabric and morphology of talus debris, their spatial variation, and the geomorphic processes presently affecting the slope. The talus presents a bi-segmented profile with a steep upper rectilinear segment and a shorter concave, basal zone. Debris are sorted by size both along (larger clasts downslope) and across the talus (larger particles below the cliffs). Shape sorting is weaker, but clast sphericity increases, and elongation decreases, toward the footslope. Upper-talus fabrics (long axes parallel to talus plane and slope) show that clasts there move by sliding, while basal blocks are deposited by rockfall, which causes more iso- tropic fabrics. Field observations and botanical evidence indicate the overall significance of grain flows, which are prevalent duetoanabundantsupplyofrubbleonthe upper talus. Comparison with similar recent slopes and repeat photography suggest the Chaos talus formed swiftly following dome collapse, when much debris may have collected below the unstable rockwalls. The talus has experienced only modest sedimentation during the 20thcentury, and is currently affected by 'normal' mass-wasting processes, which also include snow avalanches and debris flows.

Dopamine, dobutamine, and phentolamine effects on pulmonary vascular mechanics

The pressure-flow (P-Q) relationship of the pulmonary vasculature, in an isolated canine lobe perfused under classical zone II conditions, can be characterized by a rectilinear segment at high flow, a curvilinear segment at low flow, and a pulmonary arterial pressure (Ppa) that exceeds alveolar pressure at zero flow. This demonstrates the presence of critical closure in the pulmonary vascular bed. Effects of drugs on pulmonary vascular resistance (PVR) must take the normal P-Q relationship into account. We examined the effect of dopamine (D) and dobutamine (DB), alone and in combination with phentolamine (P), on the slope of the rectilinear segment of the P-Q curve (equivalent to vascular conductance), the extrapolated Ppa intercept (Ppai), and the Ppa at zero flow (Ppaz). Low-dose D (0.4–0.8 mg) and DB (1.0–5.0 mg) did not significantly alter any parameter from control. Higher-dose D (1.2–6.8 mg) and DB (13–38 mg) decreased vascular conductance 32.3 +/- 12.1 (SE) to 50.45 +/- 5.6% (P less than 0.05), and P alone increased conductance 12.0 +/- 2.6% (P less than 0.01) from control with no significant effect on Ppai or Ppaz. The change in conductance with D and DB alone was abolished when either drug was given in combination with P. Ppaz and Ppai decreased significantly from control with DB in combination with P when no significant effect on vascular conductance was noted. The results suggest that lung vessels determining changes in flow resistance are pharmacologically distinct from those subserving critical closure in the pulmonary vascular bed.