Field measurements of aerodynamic pressures in tunnels induced by high speed trains

The passage of high speed trains causes aerodynamic effects in tunnels, and considerable pressure transients are generated because of the restricted airspace within the tunnel. This leads to passenger discomfort, noise surrounding the tunnel, resistance to train movement, and possible damage to the train body and tunnel facilities. For the real assessment of the aerodynamic pressures in the tunnel induced by the passing trains of the high speed rail in Taiwan, a series of field measurements were performed near the portal and the shaft or the adit of the tunnel during normal operation. The measurements were conducted for several train speeds, including the maximum operation speed of the high speed rail in Taiwan, which is 300 km/h. Pressure sensors were deployed along the tunnel to investigate the propagation of pressure waves. The results show that the train nose entry/exit generated a compression wave propagating throughout the tunnel, resulting in a sharp increase in pressure. Conversely, the train tail entry/exit generated an expansion wave causing a pressure drop. The successive reflections of these pressure waves between both ends of the tunnel were observed. The pass-by of a train inside the tunnel also induced an immediate local pressure drop due to aerodynamic drag. Based on the measurement results, the spatial variation of the train-induced pressure peaks inside the tunnel is discussed. Furthermore, the relationship between the pressure peaks and the train speed is established, and the influence of the cross-sectional area of the tunnel is also presented.     

Geographical and annual variation in lipophilic shellfish toxins from oysters and mussels along the south coast of Korea

To better understand critical aspects of diarrhetic shellfish poisoning (DSP) occurrence in a chief producing region of bivalves in Korea, the geographical and annual variation of DSP toxins and other lipophilic toxins in mussels (Mytilus galloprovincialis) and oysters (Crassostrea gigas) were investigated by liquid chromatography-tandem mass spectrometry in an area on the south coast of Korea from 2007 to 2009. The total lipophilic shellfish toxin (LST) levels in bivalves showed geographical and annual variations. LSTs were detected mostly in the hepatopancreas of mussels from Jinhae Bay throughout the entire year, except in November and December of 2007, but were almost undetectable in all samples during the entire year in 2009. The peak DSP toxin (okadaic acid plus dinophysistoxin 1) levels in the hepatopancreas of mussels from Jinhae Bay and the Tongyeong region were 945.3 and 37.6 ng/g, respectively. The DSP toxin content was about 10 times higher in mussels than in oysters collected from the same region. The major toxins in bivalves were okadaic acid and dinophysistoxin 1; however, pectenotoxin 2 or yessotoxin was occasionally detected as a major component. The results of a quantitative analysis of phytoplankton showed that Dinophysis acuminata was the most probable source of the LSTs, with the exception of yessotoxin. When the highest DSP toxin level was measured (945.3 ng/g in the hepatopancreas of mussels from Jinhae Bay), the toxin concentration in whole mussel tissue was calculated to be 114.0 ng/g. The calculated highest DSP toxin level in whole oyster tissue from both regions was 15.0 ng/g. The calculated maximum toxicities in whole mussel and oyster tissues were lower than the regulatory limit (160 to 200 ng/g) in Korea, the European Union, and the United States. Korean oysters (242 samples) and mussels (214 samples) were thus deemed safe for consumption. But because such variation was detected in a relatively small area of the coast, it is possible that at some locations or during a specific period LST levels could exceed the standard and a few consumers could be at risk of experiencing DSP.     

Optimal pairing computation over families of pairing-friendly elliptic curves

Vercauteren introduced the concept of optimal pairing, which by definition can be computed by using at most (log₂ r)/φ(k) + log₂ k basic Miller iterations, where r is the order of the groups involved and k is the embedding degree Vercauteren (IEEE Trans Inf Theory 56(1):455–461, 2010). Freeman et al. summarized and proposed all of the new constructions of pairing-friendly elliptic curves that currently exist Freeman et al. (J Cryptol 23(2):224–280, 2010). In this paper, we give an optimal pairing for each family of pairing-friendly curves in Freeman et al. (J Cryptol 23(2):224–280, 2010) by taking the Ate or R-ate pairing approach.