A Study on the Temperature Distribution in the Shipping Cask of Spent Nuclear Fuels at LOCA

In this paper, the authors studied the temperature distribution in a shipping cask of spent nuclear fuels at LOCA (loss-of-coolant accident) after a failure of the cask. The calculation was made on a model of a uni-axial (in radial direction) thermal transfer. The result shows that the decay heat which cannot be cooled down will cause the temperature to go over 1000°C at the central part of the cask. A very dangerous accident will occur at such a high temperature ; i.e. , the vapor of cesium, a radioactive isotope, will flow out from the cask into air, and the water-metal reaction will produce a great deal of heat and hydrogen. Because of this, the nuclear fuels at the central part will collapse and melt down

A Study on the Failure of Partially Thinned Pipes under External Pressure

It is very important to prevent a buckling of thin pipes, such as are in the heat-exchanger system of PWR (pressurized water reactor), which occurs by external pressure. The design code in ASME Sec. Ill NB considers this point. However, the thickness of the pipe is partially thinned down by the steam-liquid flow in service. In the design step, no consideration has been paid to such a partially thinned down pipe, though much attenion should be given to this matter. In this paper, we discuss the pressure at the failure of the partially thinned pipe under external pressure. Experimental results show that the failure occurs at an unexpectedly small pressure, if the thinned part has some expansion, such as area. Also, the pressure at the failure does not follow the buckling equation given by the elasticity for a thin cylinder

Robust Pitch Detection by Narrow Band Spectrum Analysis

This paper proposes a new technique for detecting pitch patterns which is useful for automatic speech recognition, by using a narrow band spectrum analysis. The motivation of this approach is that humans perceive some kind of pitch in whispers where no fundamental frequencies can be observed, while most of the pitch determination algorithm (PDA) fails to detect such perceptual pitch. The narrow band spectrum analysis enable us to find pitch structure distributed locally in frequency domain. Incorporating this technique into PDA's is realized to applying the technique to the lag window based PDA. Experimental results show that pitch detection performance could be improved by 4% for voiced sounds and 8% for voiceless sounds

Accent Phrase Segmentation by Finding N-Best Sequences of Pitch Pattern Templates

This paper describes a prosodic method for segmenting continuous speech into accent phrases. Optimum sequences are obtained on the basis of least squared error criterion by using dynamic time warping between F0 contours of input speech and reference accent patterns called 'pitch pattern templates'. But the optimum sequence does not always give good agreement with phrase boundaries labeled by hand, while the second or the third optimum candidate sequence does well. Therefore, we expand our system to be able to find out multiple candidates by using N-best algorithm. Evaluation tests were carried out using the ATR continuous speech database of 10 speakers. The results showed about 97% of phrase boundaries were correctly detected when we took 30-best candidates, and this accuracy is 7.5% higher than the conventional method without using N-best search algorithm

The Use of F0 Reliability Function for Prosodic Command Analysis on F0 Contour Generation Model

This paper describes a method of utilizing an ``F0 Reliability Field'' (FRF), which we have proposed in our previous work, for estimating prosodic commands on F0 contour generation model. This FRF is the time-frequency representation of F0 likelihood, and an advantage of FRF is that it is not necessary to consider F0 errors that occur during an automatic F0 determination. Therefore, it is thought that FRF can be a more useful feature for automatic prosody analyses than F0 contour, and our previous paper has reported the validity of FRF on the analysis of detecting prosodic boundaries in Japanese continuous speech. Moreover, in this paper, we have examined the validity on the prosodic command estimation of superpositional model. Experimental results show that the accuracy of command estimation with FRF is well and it is close to the accuracy of command estimation with ideal F0 contour that has no F0 error