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Thermal comfort has been the main target of the ventilation in subway systems. However, pollutant concentration and aerosol dispersion could be the leading health issues in underground metro stations. This study numerically simulated a train movement inside a subway system using the Dynamic Mesh Technique for a 3-D computational domain consisting of four stations and connecting tunnels. The effects of both the ventilation system and the train-induced fluid flow inside the subway system were investigated. Then, the particle generation and dispersion due to train braking are considered, and the impact of the ventilation system on reducing the particle concentration inside the station was investigated. It is shown that the airflow inside the subway system is entirely affected by the piston effect. The airflow generated by the train movement is much higher than that generated by the operation of the ventilation system when only one train passes through the tunnel. The results show that the ventilation system, consisting of the supply and exhaust fans inside the tunnel and supply grilles inside the platform, can reduce the particle concentration by half, except for the platform beside the stopped train when the train enters the station and during half of the train stop time. The other design concept demonstrates that the under-platform exhaust system considerably reduces the concentration of the particles released by the train braking system on the trackside platform.

A pin-on-disc tribometer situated in a sealed cylindrical chamber was redesigned and used to find out the correlation between pellets properties and generated particles. To understand the results, it is important to understand the dust particle transport behavior inside the chamber. This could be achieved by using a simulation method. With the simulation, it is also possible to determine the operational parameters which in turn could be used to obtain good experimental results. Therefore, a model was built based on the same geometry as the particle measurement system. The flow field was firstly solved with the renormalized group (RNG) k-e turbulence model. Thereafter, a simplified drift-flux method was applied to simulate the particle transport inside the test chamber. Two important characteristics, gravitational separation and diffusion are considered in the modelling. Three groups of particles with different diameters (1nm, 1μm and 10μm) were released at the contact area between the pellets. The simulation results show that the influence of gravitational setting on particle transport is noticeable for 10μm particles, while the influence can be neglected for 1nm and 1μm. On the other hand, the diffusion has a lesser effect on particle dispersion for 1nm, 1μm and 10μm particles. Moreover, the particle loss rate was estimated by the ratio between the amount of released and escaped particles in elapsed time. The results show that the measurable portion of large micro-particles can be increased by increasing the inlet air velocity., QC 20161122

The study compared the effects of Acceptance and Commitment Therapy (ACT) with Tinnitus Retraining Therapy (TRT) on tinnitus impact in a randomised controlled trial. Sixty-four normal hearing subjects with tinnitus were randomised to one of the active treatments or a wait-list control (WLC). The ACT treatment consisted of 10 weekly 60 min sessions. The TRT treatment consisted of one 150 min session, one 30 min follow-up and continued daily use of wearable sound generators for a recommended period of at least 8 h/day for 18 months. Assessments were made at baseline, 10 weeks, 6 months and 18 months. At 10 weeks, results showed a superior effect of ACT in comparison with the WLC regarding tinnitus impact (Cohen's d = 1.04), problems with sleep and anxiety. The results were mediated by tinnitus acceptance. A comparison between the active treatments, including all assessment points, revealed significant differences in favour of ACT regarding tinnitus impact (Cohen's d = 0.75) and problems with sleep. At 6 months, reliable improvement on the main outcome measure was found for 54.5% in the ACT condition and 20% in the TRT condition. The results suggest that ACT can reduce tinnitus distress and impact in a group of normal hearing tinnitus patients.

QC 20120206

Most modern passenger cars have disc brakes on the front wheels. Unlike drum brakes, disc brakes are not sealed off from the ambient air. During braking, both the rotor and the pads wear, and this wear process generates particles that may become airborne. In field tests it is difficult to distinguish these particles from others in the environment. It is thus preferable to conduct tests using laboratory test stands where the cleanness of the surrounding air can he controlled. However, the validity of results from these test stands Should be verified by comparison with field tests. This article presents a comparison of the number and Volume distributions of airborne wear particles as measured online in field tests, in a disc brake assembly test stand, and in a pin-on-disc machine. In all cases, grey cast iron rotors and low metallic pads were tested. A promising correlation between the three different test methods is shown. The number- and volume-weighted mean particle diameter for all test methods is about 0.4 and 2-3 mu m, respectively., authorCount :5