Multiphase (more than three phases) drives possess interesting advantages over conventional three-phase drives. Over the last years, various topics related to the extension of the classical control schemes to these specifics drives have been covered in depth in literature, such as vector control of a six-phase induction machine with two sets of three-phase stator windings spatially shifted by 30 electrical degrees (also called asymmetrical dual three-phase ac machine). In this paper, a model-based predictive control (MBPC) for the current regulation of asymmetrical dual three-phase AC machines is analyzed. MBPC overcomes the difficulties of multiphase current control, avoiding complex controllers and modulation techniques, but at the expense of an increased computational cost. Simulation results are provided to examine the potential of the control method. The influence of the number of voltage vectors considered to evaluate the predictive model is studied, and different cost functions are analyzed. The computation time needed for the implementation of the control method is discussed to prove its real-time feasibility. Finally, experimental results are given to illustrate the capability of the control method.

Purpose: This paper aims to explore the image of travel destinations after the visit by analysing sentiment orientation of the online reviews, and how this orientation, as well as other electronic word of mouth (eWOM)’s credibility sources, can affect the perceived helpfulness of shared opinions measured through the helpfulness score. Design/methodology/approach: Tourist destinations are increasingly affected by travel-related information shared through the Web. More and more people first check the previous travel experiences of other people to build their own destination image and to help them in their choice of destination. This paper analyses the shared opinions related to the city of Barcelona in a well-known eWOM website. The reviewers’ opinion and the credibility sources of eWOM are extracted from the web using a webscraper, while the sentiment score to analyse the discourse orientation (positive vs negative) is calculated using computer-based sentiment analysis techniques. Findings: Online reviews’ users are reluctant to provide extreme polar opinions (very negative, very positive) to any travel subcategory (hotel, restaurant, attractions and night-life) of a tourist destination. The results obtained also reveal that eWOM’s perceived helpfulness grows with the expertise of the reviewer. However, the helpfulness score given to the reviews posted is not influenced by the sentiment orientation of the author’s opinion. Research limitations/implications: This research is limited to the case study of Ciao, which is a well-known consumer platform, and the city of Barcelona, which is a top touristic destination. However, the approach proposed can be easily extended to other similar consumer platforms and cities using the same methodology. Practical implications: Understanding the information posted in the media environment is a major concern in the field of marketing destination planning. Positive and negative eWOM offers potential consumers a clear picture on the tourist destination, and this information can be used by Destination Marketing Organisations to meet customers’ needs and expectations. The perceived helpfulness of reviews analysed in this paper can also help practitioners and scholars to understand those factors that make reviews more trustable. Originality/value: From a methodological point of view, the main contribution of this research is the utilisation of an unstructured approach to the measurement of the destination image based on the sentiment analysis of shared opinions. From a theoretical point of view, the study relates the post-visit destination image with the pre-visit image formation process, using the sentiment orientation of the former and the perceived helpfulness of the latter.

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and a reduction in the total power per phase are required. Strategies derived from the conventional field-oriented control have been traditionally used in high-performance speed-control applications of multiphase drives. The well-known direct torque control (DTC) technique has been also applied in the multiphase case, but the achieved performance with a hysteresis-control-based approach is far from that obtainable with the three-phase drive, although the control structure is actually more complex. In this paper, a predictive-torque-control method is introduced as an alternative to the DTC technique for the high-performance variable-speed operation of multiphase drives. Simulation and experimental results are provided to illustrate the properties of the developed method.

The application of scientific tools to analyse the use of Internet-based e-learning tools in academic settings is in general an ignored area. E-learning tools are actually an emergent topic as a result of the new ideas introduced by the European Higher Education Area. Lifelong learning, or the promotion of student initiative, is the new paradigm of a learner-centred education. In this context, e-learning tools can represent an effective way of supporting this new trend in education. Assuming the premise that successful use of these web-based tools depends primarily on a user's behaviour, the objective of this research is to examine the technology acceptance model (TAM) of web-based e-learning tools used in practical and laboratory teaching. The research hypotheses derived from this model have empirically been validated using the responses to a survey on e-learning usage among 220 users. These responses have been examined through partial least square. The obtained results strongly support the extended TAM in predicting a student's intention to use e-learning and define a set of external variables with a significant influence in the original TAM variables. Surprisingly, perceived ease of use did not posit a significant impact on student attitude or intention towards e-learning tool usage. Therefore, early evaluation of e-learning material is considered essential to providing a framework for further improvements of the tool.

The interest in predictive control approach and multiphase drives has been steadily growing during the last decade. Predictive control techniques have been recently introduced as a viable alternative to conventional PI controllers with carrier-based or space vector PWM techniques in the current regulation of multiphase power converters and drives. The developed schemes have demonstrated a good performance at the expense of a high computational cost, an unknown switching frequency, and the appearance of large undesirable stator current harmonic components. In this paper, an enhanced predictive current control technique with fixed switching frequency is introduced for an asymmetrical dual three-phase ac drive. Fast torque and current responses are achieved while favoring stator current harmonic suppression. The experimental results are provided to verify the benefits of the proposed control method when compared to the other existing predictive control methods.