Benchmark Evaluation of HOG Descriptors as Features for Classification of Traffic Signs

The purpose of this paper is to analyze the performance of the Histograms of Oriented Gradients (HOG) as descriptors for traffic signs recognition. The test dataset consists of speed limit traffic signs because of their high inter-class similarities.   HOG features of speed limit signs, which were extracted from different traffic scenes, were computed and a Gentle AdaBoost classifier was invoked to evaluate the different features. The performance of HOG was tested with a dataset consisting of 1727 Swedish speed signs images. Different numbers of HOG features per descriptor, ranging from 36 features up 396 features, were computed for each traffic sign in the benchmark testing. The results show that HOG features perform high classification rate as the Gentle AdaBoost classification rate was 99.42%, and they are suitable to real time traffic sign recognition. However, it is found that changing the number of orientation bins has insignificant effect on the classification rate. In addition to this, HOG descriptors are not robust with respect to sign orientation.

Democracy lessons in market-oriented schools : The case of Swedish upper secondary education

Based on recent ethnographic research, this article explores young people’s opportunities of formal and informal democracy learning and expressions of such learning in the highly market-influenced Swedish upper secondary education. With its ambitious democracy-fostering goals and far-reaching marketisation, Swedish education constitutes an interesting case in this respect. The analysis indicates that ‘voting with the feet’ emerges as an important way of exerting student influence. At the same time, young people’s voice is surprisingly neglected in classroom practice. Increased focus on performance and goal attainment tends to overshadow less ‘rewarding’ aspects of the curriculum, such as democracy teaching and learning, both from the side of teachers and students. Students are also increasingly expected to act as school representatives and to avoid giving negative impressions of their school.