Stability limits for tokamak plasma with negative triangularity
Negative triangularity tokamak plasmas are subject of an increased interest both in existing experiments and in studies of core physics as well as power handling relevant to the fusion demonstration power reactor. The ideal MHD stability calculations for the negative triangularity plasma extend the investigation of the TCV tokamak beta limits and edge stability to double null shapes, lower aspect ratio and negative shear. In case of the negative triangularity, the 2nd stability access is closed for ballooning modes and a well defined limiting pressure gradient profile exists in the positive shear region. The external kink mode stability limit can be obtained by rescaling the limiting profiles. H-mode discharges with upper negative triangularity in TCV demonstrate significant mitigation of type I ELM peak power losses. This is consistent with lower edge stability limits for the pedestal. For double null negative triangularity configurations higher pedestals can be stable due to higher shear at low pedestal current density. At the same time a destabilization of a whole range of fixed boundary modes takes place, once the Mercier criterion for localized modes is violated, implying possible changes in the ELM characteristics. In particular, the diamagnetic stabilization on the edge stability is much less effective than in a standard case when peeling-ballooning modes set pedestal height limit.
Stability of snowflake Diverted and Negative Triangularity Plasmas in the TCV Tokamak
Reference EPFL-CONF-148359 URL: http://epsppd.epfl.ch/ URL: http://crpplocal.epfl.ch/pinboard/papers/095003103.pdf Record created on 2010-04-15, modified on 2017-05-12
Automatic classification of TV news articles based on telop character recognition
The purpose of this study is to develop a multimedia database system for TV news video data. TV news video data consist of speech, characters and images. In this study, telop characters are recognized and given to the news articles as indices for classification. At first, telop frames which include telop characters are detected and then the telop characters are extracted and recognized. Through morphological analysis of the recognized telop characters, keywords are extracted which consist of more than two characters. Their keywords are used as indices to classify the TV news articles. We carried out experiments for 30 days of NHK 5 minutes news and obtained 95.4% telop character extraction rate, 81.4% character recognition rate and 83.8% article classification rate. We improved the article classification rate by 43.4% through character recognition improvement from 44.1% to 81.4%.