The force transmissibility of a floating slab track
The force transmissibility of a track isolation system is the ratio of the force transmitted to the track bed over the force applied at the railheads. This paper focuses on the force transmissibility of a double-tie or ‘mini-slab’ floating slab track installation. The power spectral densities of the forces transferred to ground due to ‘white noise’ force sources at the rail heads are calculated. Analytical models and the Finite Element (FE) method are used to analyse a floating slab track supported on a rigid foundation. The effect of rail fastener stiffness is discussed. The influence of the flexibility of the floating slabs and the effects of a non-rigid foundation on the force transmissibility is investigated within the framework of the FE method.
Structure-Borne Noise and Vibration Control for Chatswood Interchange
The Chatswood Interchange project is a transit-oriented development combining multi-family residential and commercial development with a commuter rail station in Chatswood, NSW, Australia. The train station and garage structure would directly support 40-storey residential condominium towers and commercial spaces without benefit of structural breaks or building isolation. The vibration control provisions incorporated into the design include floating slab track, a massive and thick concrete deck, and large cross-section columns. Structure-borne noise and vibration levels were predicted with a finite element model, using an enforced relative displacement between wheel and rail. The predicted structure-borne vibration levels were compared with vibration levels measured at the top of the station structure during partial completion and found to be in reasonable agreement with prediction.
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.