The optimal design of risers for castings has been the subject of numerous investigations and this paper determines the optimal dimensions when Chvorinov’s rule for solidification is obeyed by both the riser and casting and solidification time is the only constraint involved .This problem can be formulated to minimize the riser volume subject to the constraint that the riser solidification time...

The problem of suppressing the slugging phenomenon is investigated. Industrial oil facilities such as gas-lifted wells and offshore production oil-risers are examples of systems where occurs such phenomenon. To study this problem, we consider that these systems are written as a set of 3 × 3 hyperbolic partial differential equations of balance laws, where the control variable appears at the boun...

We have studied the temperature dependence of the integer quantum Hall transitions in the molecular crystal (TMTSF)2PF6. We find that the transition width between the quantum Hall plateaus does not exhibit the universal power-law scaling behavior of the integer quantum Hall effect observed in semiconducting devices. Instead, the slope of the ρxy risers, dρxy/dB, and the (inverse) width of the ρ...

Vortex induced vibrations (VIV) of long flexible risers subjected to ocean currents exhibit a strongly nonlinear phenomenon. Although significant efforts have been done for the frequency or time-frequency analysis of this complicated phenomenon, an effective method is still lacking. The objective of this paper is to provide a new method — a Prony-based method — for analyzing the time-varying fr...

The Oil and gas exploration is one of the most strategic industrial sectors in Brazilian economy. discovery deep water reserves adds more difficulty to already problematic use materials equipment extremely corrosive environments. With objective increasing service life equipment, consequently reducing cost maintenance preventing against environmental catastrophes, it common CRA claddings via wel...

The expansion of a deepwater brownfield may become necessary to increase the production hydrocarbons. Such often requires installation additional risers existing floating platform. However, seabed footprint facilities be congested with subsea pipelines and structures. Tying back such as steel catenary riser (SCR) platform becomes challenging. Floating (FCR) is novel solution bends or ‘waves’ cl...

Abstract Gas-solid riser flow exhibits strong heterogeneous structure in both axial direction and radial directions. Recent experimental studies reveal that the general radial solids concentration profiles present a double ring structure and the formation of a solid core region which have a relative higher concentration than the annulus region. This paper is focused on a comprehensive modeling ...

BACKGROUND A low level of physical activity impacts mental as well as physical health. This study investigated the daily lifestyle habits that affect physical activity in young children. METHODS The relationship between physical activity, assessed by means of a Mini-Mitter Actiwatch device, and observed daily lifestyle habits was analyzed for 204 children, aged 12 to 40 months (average: 22.6 ...