This paper analyses the capabilities of different techniques to build a semantic representation of educational digital resources. Educational digital resources are modeled using the Learning Object Metadata (LOM) standard, and these semantic representations can be obtained from different LOM fields, like the title, description, among others, in order to extract the features/characteristics from the digital resources. The feature extraction methods used in this paper are the Best Matching 25 (BM25), the Latent Semantic Analysis (LSA), Doc2Vec, and the Latent Dirichlet allocation (LDA). The utilization of the features/descriptors generated by them are tested in three types of educational digital resources (scientific publications, learning objects, patents), a paraphrase corpus and two use cases: in an information retrieval context and in an educational recommendation system. For this analysis are used unsupervised metrics to determine the feature quality proposed by each one, which are two similarity functions and the entropy. In addition, the paper presents tests of the techniques for the classification of paraphrases. The experiments show that according to the type of content and metric, the performance of the feature extraction methods is very different; in some cases are better than the others, and in other cases is the inverse.

In this work, the affective state of users in virtual learning environments is assessed/recognized in terms of continuous arousal and valence dimensions, making use of multimodal information (audio, text and video), whenever any of these modalities are available. In general, virtual learning environments where these three modalities are all the time, are not common; at some moments only the video modality is available, while in others only text or/and video and/or audio. Different approaches using feature-level fusion and decision-level fusion are proposed for multimodal recognition with missing data. Recognizing according to available modalities is studied following the ideas of dropout from neural networks and of variable input length from recurrent neural networks. This proposal is innovative because it represents emotions in the continuous space, which is not common in virtual education; and makes use of the available modalities in a virtual environment in a given moment, which is very common in virtual learning environments because the people are not speaking or writing all the time.

In this work, we aim to analyze the sentiments of learning resources from their textual contents. This work proposes a method for automatic assignment of emotional state to learning resources, based on their feature similarity with previously labeled learning resources. Then, various feature extraction strategies, which describe the relevant information in the texts, are compared for the task of sentiments analysis, considering the two main dimensions of emotions: arousal and valence. The results are very promising, showing a very high value in the performance metrics, like the $$R^2$$R 2 score.

Coffee Leaf Rust (CLR) is a fungal epidemic disease that has been affecting coffee trees around the world since the 1980s. The early diagnosis of CLR would contribute strategically to minimize the impact on the crops and, therefore, protect the farmers’ profitability. In this research, a cyber-physical data-collection system was developed, by integrating Remote Sensing and Wireless Sensor Networks, to gather data, during the development of the CLR, on a test bench coffee-crop. The system is capable of automatically collecting, structuring, and locally and remotely storing reliable multi-type data from different field sensors, Red-Green-Blue (RGB) and multi-spectral cameras (RE and RGN). In addition, a data-visualization dashboard was implemented to monitor the data-collection routines in real-time. The operation of the data collection system allowed to create a three-month size dataset that can be used to train CLR diagnosis machine learning models. This result validates that the designed system can collect, store, and transfer reliable data of a test bench coffee-crop towards CLR diagnosis.