The Revisiting Problem in Simultaneous Localization and Mapping: A Survey on Visual Loop Closure Detection

Where am I? This is one of the most critical questions that any intelligent system should answer to decide whether it navigates to a previously visited area. This problem has long been acknowledged for its challenging nature in simultaneous localization and mapping (SLAM), wherein the robot needs to correctly associate the incoming sensory data to the database allowing consistent map generation. The significant advances in computer vision achieved over the last 20 years, the increased computational power, and the growing demand for long-term exploration contributed to efficiently performing such a complex task with inexpensive perception sensors. In this article, visual loop closure detection, which formulates a solution based solely on appearance input data, is surveyed. We start by briefly introducing place recognition and SLAM concepts in robotics. Then, we describe a loop closure detection system's structure, covering an extensive collection of topics, including the feature extraction, the environment representation, the decision-making step, and the evaluation process. We conclude by discussing open and new research challenges, particularly concerning the robustness in dynamic environments, the computational complexity, and scalability in long-term operations. The article aims to serve as a tutorial and a position paper for newcomers to visual loop closure detection.Comment: 25 pages, 15 figure

Defect detection using weakly supervised learning

In many real-world scenarios, obtaining large amounts of labeled data can be a daunting task. Weakly supervised learning techniques have gained significant attention in recent years as an alternative to traditional supervised learning, as they enable training models using only a limited amount of labeled data. In this paper, the performance of a weakly supervised classifier to its fully supervised counterpart is compared on the task of defect detection. Experiments are conducted on a dataset of images containing defects, and evaluate the two classifiers based on their accuracy, precision, and recall. Our results show that the weakly supervised classifier achieves comparable performance to the supervised classifier, while requiring significantly less labeled data

Confronting Pharmaceutical Products Selection Criteria: A comparative survey of consumers in Greece, France and Bulgaria

Purpose: The survey at hand explores the factors describing the consumers’ profile in the pharmaceutical markets of three European nations Design/methodology/approach: A primary research was carried out using questionnaires with a sample of citizens (pharmacy customers) in the capital of each nation and aiming to to determine the criteria motivating the customer/patient to purchase particular pharmaceutical preparations and the ultimate goal is to get an objective picture of the buying behavior of Greek, French and Bulgarian consumers Findings: Behavioral motives appear to be affected by health scientists, price, advertising, alternative available options and “public opinion”. Moreover, it appears that customers differ from one nation to the other but also between themselves, both with respect to their choices, as well as their special mode of action. Such individuality mainly results from the different levels of education and basic income of each pharmaceutical products consumer. Comparative study reveals that Frenchmen, Greeks and Bulgarians tend to agree in some common behavioral trends, yet substantially differ in issues of major importance. Research limitations/implications: Any research on the quantitative measurement of perceptions has inherent limitations as it rests on the subjective views and attitudes of the respondents. Additionally, some obstacles emerged in the course of the survey and in regard to the filling-out of the questionnaires in all three countries, thus account must be taken of the following limitations when interpreting the findings: (1) lack of detailed knowledge of the legislative framework for the supply of pharmaceutical products in Bulgaria and France; (2) rapid changes in external factors (legal-political-social) in the case of Greece; (3) inability of personal contact with every respondent in order to get a first-hand view of their “pharmaceutical behavior” and education, and (4) time and resources limitations dictated that the survey be carried out with respect to a very limited and small sample compared to the total population of Athens, Paris and Sofia. Originality/value: This research effort was motivated by former researches relating to the consumers of pharmaceutical products, the knowledge gap that was created with respect to this issue during the years of the financial and more general crisis and the continuous changes in the health system of Greece. The idea for a comparative survey then rested on the practical and substantial comparison of consumers from Greece and those from the two other nations. It was simultaneously reinforced by the fact that no other similar research effort (for Greece-France-Bulgaria) has been published in recent years