Numerical Simulation of Air Flow Properties around High Speed Train in Very Long Tunnel
Numerical simulation of air flow disturbed around a train body with different angle of train nose and different velocity of high speed train in a very long tunnel have been made. Three-dimensional flow theory is capable of modeling the effects of interest in the tunnel environment. The scale of train is 2500mm×320mm×427mm length×width×heigh, and the scale of tunnel is 150m×10.4m×8.2m length×width×heigh. Train speed is 432km/h, 500km/h and 600km/h respectively. The distributions of pressure, velocities streamline and second flow around high speed train in a very long tunnel space can be obtained by simulating. Results show that the train nose angles and train speed affects the air flow around the train strongly. The pressure drag increases with rising of the nose angles and train speed, and it reaches to the highest value of 23073 Pa when the angle is 60 0 and 32466Pa as the velocity is 600km/h. The air velocity in the annular space is quite enormous and the maximize value is 178m/s with train nose 60 0 and 247m/s with train speed 600km/h. The simulation results can be taken to help us for study the high-speed train energy-consuming, maximum velocity, safety and stabilization when it running in a very long tunnel.
Place of birth
The management of childbirth is continuously evolving, reflecting changes in clinical, psychological, and social factors. In the past 50 years there have been dramatic falls in perinatal and maternal mortality, a steady increase in the amount of technological intervention in the management of labour, and a change in the roles of members of the maternity care team.



Percentage of women giving birth in United Kingdom in 1890–1990 who gave birth in hospital



Over the past 60 years the proportion of births at home has fallen markedly from 80% in 1930 to 1% in 1990, but in the past eight years the proportion has begun to rise again. Some studies suggest that 10–14% of women would choose this option if given the opportunity. A similar trend has been seen in all Western countries except the Netherlands, where, in 1995, 32% of births still occurred in the home.



Percentage of women giving birth in England and Wales in 1980–94 who gave birth at home



When considering how a birth is to be conducted, attention must be given to both risks and benefits. The debate over the place of birth raises many fundamental questions about the general management of labour, patients‘ satisfaction, and women's rights to choose their form of care. Much professional and lay discussion has taken place on many aspects of pregnancy care, brought into focus by the Department of Health's 1993 report Changing Childbirth , which indicated the way the maternity services may develop. Safety is the foundation of good maternity care but this must take into account the emotional as well as the physical wellbeing of mother and baby.

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The home is the place for the practice of midwifery, not obstetrics, and the principal provider of care will be the midwife. The home is therefore appropriate for mothers with …
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.