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Reliable tracking of moving boundaries is important for the simulation of compressible fluid flows, and there are a lot of contributions in literature. We recognize from the classical piston problem, a typical moving boundary problem in gas dynamics, that acceleration is a key element in the description of the motion and should be incorporated into the design of a moving boundary tracking method. Technically, the resolution of the accelerated piston problem boils down to a one-sided generalized Riemann problem solver, which is taken as the building block for constructing schemes with high order accuracy in both space and time. In this paper we take this into account, together with the cell-merging approach, to propose a new family of high order accurate moving boundary tracking methods and verify its performance through one- and two-dimensional test problems, along with accuracy analysis. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the accuracy rate of bronchopulmonary dysplasia (BPD) diagnosis and risk factors of short-term poor prognosis for premature infants. This study analyzed the clinical data of 81 premature infants (<32 weeks gestational age) with BPD, who were on oxygen therapy >28 days, and survived >36 weeks (corrected age). Outcome measures included treatments, conditions on the 28th day after birth, oxygen therapy conditions at the 36th week, occurrence of any serious complications during hospital stay. The major risk factors affecting prognosis were ventilation duration, duration of oxygen therapy, application of steroids, hypothyroidism and severity of BPD (all P<0.05). Interventions for complications (n=53) resulted in ceased inhalation of oxygen in 12 infants, improvement of symptoms in 26 infants, and were ineffective in 15 infants. BPD prognosis can be improved by shortening the duration of invasive ventilation and correcting thyroid function. [ABSTRACT FROM AUTHOR]

In this paper we develop a novel two-stage fourth order time-accurate discretization for time-dependent flow problems, particularly for hyperbolic conservation laws. Different from the classical Runge-Kutta (R-K) temporal discretization for first order Riemann solvers as building blocks, the current approach is solely associated with Lax-Wendroff (L-W) type schemes as the building blocks. As a result, a two-stage procedure can be constructed to achieve a fourth order temporal accuracy, rather than using the well-developed four-stage procedure for R-K methods. The generalized Riemann problem (GRP) solver is taken as a representative of L-W type schemes for the construction of a two-stage fourth order scheme. [ABSTRACT FROM AUTHOR]