Bottom-Pressure Development Due to an Abrupt Slope Reduction at Stepped Spillways

Fluctuating bottom-pressures on stepped chutes are relevant for the spillway design. An abrupt slope reduction causes a local alteration of the bottom-pressure development. Little information is available regarding the air–water flow properties near an abrupt slope reduction on stepped chutes, particularly on the local pressure evolution. Nevertheless, the option of providing a chute slope reduction may be of interest in spillway layout. The experiments presented herein include pressure distributions on both vertical and horizontal step faces, subsequent to an abrupt slope reduction on stepped chutes. A relatively large-scale physical model including abrupt slope reductions from 50° to 18.6° and from 50° to 30° was used, operated with skimming flow. The data indicate a substantial influence of the tested slope reductions on the bottom-pressure development. In the vicinity of the slope reduction, the mean pressure head near the edge of the horizontal step face reached 0.4 to 0.6 times the velocity head upstream of the slope reduction, for critical flow depths normalized by the step height ranging between 2.6 and 4.6.

Three-Dimensional Turbulence Numerical Simulation of Flow in a Stepped Dropshaft

The dropshaft structure is usually applied in an urban drainage system to connect the shallow pipe network and the deep tunnel. By using the renormalization group (RNG) k~ε turbulence model with a volume of fluid method, the flow pattern and the maximum relative water depth over a stepped dropshaft with a different central angle of step were numerically investigated. The calculated results suggested that the flow in the stepped dropshaft was highly turbulent and characterized by deflection during the jet caused by the curvature of the sidewall. According to the pressure distribution on the horizontal step and the flow pattern above the step, the flow field was partitioned into the recirculating region, the wall-impinging region and the mixing region. In addition, with the increase in the central angle of step, the scope of the wall-impinging region and the mixing region increased and the scope of the recirculating region remained nearly unchanged. The maximum water depth increased with the increase in discharge. In the present work we have shown that, as the value of the central angle of step increased, the maximum water depth decreased initially and increased subsequently.

A unified lattice path approach to distributions related to Markov dependent trials

For fixed integers n(= 0) and μ, the number of ways in which a moving particle taking a horizontal step with probability p and a vertical step with probability q, touches the line Y = n+μX for the first time, have been counted. The concept has been applied to obtain various probability distributions in independent and Markov dependent trials.

Numerical Investigation on the Hydraulic Properties of the Skimming Flow over Pooled Stepped Spillway

Pooled stepped spillway is known for high aeration efficiency and energy dissipation, but the understanding for the effects of pool weir configuration on the flow properties and energy loss is relatively limited, so RNG k − ε εturbulence model with VOF method was employed to simulate the hydraulic characteristics of the stepped spillways with four types of pool weirs. The calculated results suggested the flow in the stepped spillway with staggered configuration of` two-sided pooled and central pooled steps (TP-CP) was highly three dimensional and created more flow instabilities and vortex structures, leading to 1.5 times higher energy dissipation rate than the fully pooled configuration (FP-FP). In FP-FP configuration, the stepped spillway with fully pooled and two-sided pooled steps (FP-TP) and the spillway with fully pooled and central pooled steps (FP-CP), the pressure on the horizontal step surfaces presented U-shaped variation, and TP-CP showed the greatest pressure fluctuation. For FP-TP and FP-CP, the vortex development in the transverse direction presented the opposite phenomenon, and the maximum vortex intensity in TP-CP occurred at Z/W = 0.25, while FP-FP illustrated no significant change in the transverse direction. The overlaying flow velocity distribution in the spanwise direction demonstrated no obvious difference among FP-FP, FP-TP, and FP-CP, while the velocity in TP-CP increased from the axial plane to the sidewalls, but the maximum velocity for all cases were approximately the same.

VO2max Testing in Trail Runners: Is There a Specific Exercise Test Protocol?

Trail running places specific physiological demands on the human body due to its uphill and downhill running sections. We developed and investigated a more sport-specific trail exercise test protocol (inclination and speed incremental protocol), and compared it to two standard exercise test protocols (horizontal step and ramp protocol) in thirteen highly trained trail runners (age 31±6 years, height 179±6.4 cm, weight 69.2±7.9 kg, BMI 21.6±2.1 kg/m2). The maximum oxygen uptake (VO2max) measured during the trail test (62.5±5.9 ml·kg−1·min−1, [95% CI: 59.0-66.1]) was significantly higher compared to both the step test (60.1±5.3 ml·kg−1·min−1, [95% CI: 56.8-63.3], p=0.024) and the ramp test (59.7±5.5 ml·kg−1·min−1, [95% CI: 56.4-63.0], p=0.028). Time to task failure was significantly shorter in the trail test (557±73 s, [95% CI: 512-601]) compared to both the step test (1378±152 s, [95% CI: 1286-1470], p<0.001) and the ramp test (605±95, [95% CI: 547-662], p<0.001). Other physiological measurements obtained were similar. The trail test was the preferred choice in our group of trail runners. This study supports the implementation of the trail test in practice, and recommends that its validity be evaluated further.

Design of Automated Moving Stage with Adaptive Focus System to Support Microscopy Image Stitching

Image stitching is a method to obtain high-resolution images through compositing several image elements using invariant pattern recognizing and matching between each image elements involved. This method can remove resolution restriction in digital microscopy imaging. This study aims to design automated stitching with adaptive focus mechanism to achieve high-quality final stitched image. We attach three-axis microscopic actuator into Olympus CX-21 light microscope. The actuator has been programmed to support image elements capture with adaptive focus ability to compensate focus plane changes due to unevenness object surface, inhomogeneous slide thickness and imperfection of preparation holder. Testing results show automated moving stage has horizontal step resolution 0.198±0.001 μm/step with hysteresis 5.99±1.09 μm and vertical step resolution 0.197±0.004 μm/step with hysteresis 2.36±1.28 μm at maximum speed 3,675μm/sec in 16 sub-division microstep setting value. Automated moving stage has also linear response with R2=0.999. Adaptive focus testing show satisfied optimum objective height locking stability using identical factor ε=95% for every objective application below 100x. Adaptive focus success stabilizes Zopt for every image element to generate final stitched image with homogenous focus value.