Sensor development and integration for robotized laser welding

Laser welding requires fast and accurate positioning of the laser beam over the seam trajectory. The task of accurate positioning of the laser tools is performed by robotic systems. It is therefore necessary to teach the robot the path it has to follow. Seam teaching is implemented in several ways: Offline Programming, Manual Point-to-point, Sensor Guided. The first two processes are time consuming; the second requires constant human interaction, whereas the last one is fast and fully automated.\ud The most commonly used seam detection sensors are based on optical triangulation with a single structured light line. Such sensors impose restrictions on the laser tool orientation in relation to the seam trajectory. The shape of the seam trajectory in combination with the required speed, can force the robot into positioning errors due to robot dynamics. Furthermore, closed looped seam trajectories such as circles or rectangles are not possible to be taught with such sensors. \ud A solution to these problems is given by the seam detection sensor of the integrated laser welding head. The developed perimetric sensor allows the detection and following of seam trajectories without restrictions on the relative position of the welding head. This reduces positioning errors due robot dynamics and allows looped seam trajectories. \ud The developed integrated laser welding head fulfills two additional sensing functionalities: weld inspection and process monitor. The weld inspection sensor measures the weld surface properties and provides quality estimation according to ISO13919. The process monitor sensor allows the detection of the keyhole formation in full penetration welding. \ud The integration of these sensors into one compact laser welding head required the fusion of their optical paths. Automated calibration procedures have been developed for the system’s integration with robots. Finally, a user friendly sensor software application has been developed that allows access and overview of all the sensors’ processes and handles all required data communications

Sensor integration for robotic laser welding processes

The use of robotic laser welding is increasing among industrial applications, because of its ability to weld objects in three dimensions. Robotic laser welding involves three sub-processes: seam detection and tracking, welding process control, and weld seam inspection. Usually, for each sub-process, a separate sensory system is required. The use of separate sensory systems leads to heavy and bulky tools, in contrast to compact and light sensory systems that are needed to reach sufficient accuracy and accessibility. In the solution presented in this paper all three subprocesses are integrated in one compact multipurpose welding head. This multi-purpose tool is under development and consists of a laser welding head, with integrated sensors for seam detection and inspection, while also carrying interfaces for process control. It can provide the relative position of the tool and the work piece in three-dimensional space. Additionally, it can cope with the occurrence of sharp corners along a three-dimensional weld path, which are difficult to detect and weld with conventional equipment due to measurement errors and robot dynamics. In this paper the process of seam detection will be mainly elaborated

The impact of slow steaming on the carriers’ and shippers’ costs: The case of a global logistics network

We propose an analytical modeling methodology for quantifying the impact of slow steaming on the carrier's voyage cost and on the shipper's total landed logistics costs. The developed methodology can be employed by a carrier and a shipper in their contract negotiations, in order for the two parties to determine how they could divide between them the savings resulted from slow steaming. We demonstrate that the impact of slow steaming and speed adjustment policies on the shippers’ total landed logistics costs tend to increase as the vessel travels towards the end of its voyage

A real-time proximity querying algorithm for haptic-based molecular docking

Intermolecular binding underlies every metabolic and regulatory processes of the cell, and the therapeutic and pharmacological properties of drugs. Molecular docking systems model and simulate these interactions in silico and allow us to study the binding process. Haptic-based docking provides an immersive virtual docking environment where the user can interact with and guide the molecules to their binding pose. Moreover, it allows human perception, intuition and knowledge to assist and accelerate the docking process, and reduces incorrect binding poses. Crucial for interactive docking is the real-time calculation of interaction forces. For smooth and accurate haptic exploration and manipulation, force-feedback cues have to be updated at a rate of 1 kHz. Hence, force calculations must be performed within 1ms. To achieve this, modern haptic-based docking approaches often utilize pre-computed force grids and linear interpolation. However, such grids are time-consuming to pre-compute (especially for large molecules), memory hungry, can induce rough force transitions at cell boundaries and cannot be applied to flexible docking. Here we propose an efficient proximity querying method for computing intermolecular forces in real time. Our motivation is the eventual development of a haptic-based docking solution that can model molecular flexibility. Uniquely in a haptics application we use octrees to decompose the 3D search space in order to identify the set of interacting atoms within a cut-off distance. Force calculations are then performed on this set in real time. The implementation constructs the trees dynamically, and computes the interaction forces of large molecular structures (i.e. consisting of thousands of atoms) within haptic refresh rates. We have implemented this method in an immersive, haptic-based, rigid-body, molecular docking application called Haptimol_RD. The user can use the haptic device to orientate the molecules in space, sense the interaction forces on the device, and guide the molecules to their binding pose. Haptimol_RD is designed to run on consumer level hardware, i.e. there is no need for specialized/proprietary hardware

Response of Fresh Food Suppliers to Sustainable Supply Chain Management of Large European Retailers

This article analyses new supply chain management (SCM) strategies of the largest retail distribution chains in Europe within the context of differing sustainability concepts and approaches. An analysis is carried out of the strategic plans of such retailers, as well as recent developments in the sector. We begin by identifying the priority actions of retailers and then evaluating, by means of a survey, how small horticultural marketing firms (mainly cooperatives) in southeast Spain respond to the needs of these retailers. Subsequently, an analysis is carried out on these small marketing firm exporters to identify the relative weight which they assign to the variables assessed, while also considering the existing relationships between said weighted variables and business profits. Our results show that retailers tend to establish more simplified supply chains (that is, shorter and more vertical), essentially demonstrating their interpretation of a sustainable supply chain. In contrast, horticultural marketing firms have concentrated more on tactical and operational issues, thereby neglecting environmental, social and logistics management. Thus, their success rate in meeting the sustainability demands of their customers can be considered medium-low, requiring a more proactive attitude. Improved and collaborative relations, and the integration of sustainability concepts between suppliers (marketing firms) and their clients could contribute to successfully meeting sustainability demands. From the point of view of the consumer, close supplier–retail relationships have solved food safety issues, but the implementation of sustainability in other supply chain activities and processes is a pending issue. We propose strategic approximation and collaboration to bridge the gap between the varying sustainability demands in the supplier–retail relationship within perishable supply chains. Although this article specifically addresses fresh vegetable supply chains, the results may be extrapolated to other agri-food chains with a similar structure

Simulating molecular docking with haptics

Intermolecular binding underlies various metabolic and regulatory processes of the cell, and the therapeutic and pharmacological properties of drugs. Molecular docking systems model and simulate these interactions in silico and allow the study of the binding process. In molecular docking, haptics enables the user to sense the interaction forces and intervene cognitively in the docking process. Haptics-assisted docking systems provide an immersive virtual docking environment where the user can interact with the molecules, feel the interaction forces using their sense of touch, identify visually the binding site, and guide the molecules to their binding pose. Despite a forty-year research e�ort however, the docking community has been slow to adopt this technology. Proprietary, unreleased software, expensive haptic hardware and limits on processing power are the main reasons for this. Another signi�cant factor is the size of the molecules simulated, limited to small molecules. The focus of the research described in this thesis is the development of an interactive haptics-assisted docking application that addresses the above issues, and enables the rigid docking of very large biomolecules and the study of the underlying interactions. Novel methods for computing the interaction forces of binding on the CPU and GPU, in real-time, have been developed. The force calculation methods proposed here overcome several computational limitations of previous approaches, such as precomputed force grids, and could potentially be used to model molecular exibility at haptic refresh rates. Methods for force scaling, multipoint collision response, and haptic navigation are also reported that address newfound issues, particular to the interactive docking of large systems, e.g. force stability at molecular collision. The i ii result is a haptics-assisted docking application, Haptimol RD, that runs on relatively inexpensive consumer level hardware, (i.e. there is no need for specialized/proprietary hardware)

Classroom observation in second language classrooms : bridging the gap between theory and practice for pre-service and in-service teachers of Greek as an L2

This paper is a qualitative study in the framework of a broader project (LETEGR2) that aims to shed light on the way classroom-based observation might contribute to bridging the gap between teaching theory and practice and assisting teacher education. It draws on data derived from pre-service (n=15) and in-service teachers (n=6) who applied the LETEGR2 Classroom Observation protocol in second language classrooms in Greece. Both groups of data are presented according to the observation stages (pre- and post-) in which they have been collected. They are discussed as pre- and in-service teachers' "voices" in terms of the main issues they bring to the fore in relation to L2 learners' profiles, the teaching process and teachers' practices. An attempt is made to link both group of participants' observed behaviours and events to underlying theoretical concepts for second language learning and teaching.La investigació següent és un estudi qualitatiu que forma part d'un projecte més ampli anomenat LETEGR2. L'objectiu d'aquesta investigació és explicar com l'observació a l'aula pot contribuir a disminuir la bretxa entre els coneixements teòrics, la pràctica docent i la formació del professorat. Està basada en dades recollides de professors en pràctiques (n=15) i de professors en actiu (n=6) que van seguir el protocol d'Observació d'Aula del LETEGR2 en aules on s'ensenya grec com a segona llengua estrangera a Grècia. Totes les dades recollides es presenten seguint les diferents etapes d'observació en les quals han estat recollides (pre- i post-). La discussió de les dades es presenta a través de les veus dels dos grups de participants en relació als perfils dels alumnes d'una L2, el procés d'ensenyament i les pràctiques dels docents. S'intenta establir un vincle entre els comportaments i accions observades a cada grup de participants i els conceptes teòrics subjacents en el camp de l'ensenyament i aprenentatge d'una segona llengua.La presente investigación es un estudio cualitativo que forma parte de un proyecto más amplio llamado LETEGR2. El objetivo de esta investigación es elucidar cómo la observación en el aula puede contribuir a disminuir la brecha entre los conocimientos teóricos, la práctica docente y la formación del profesorado. Está basada en datos obtenidos de profesores en prácticas (n=15) y profesores en activo (n=6) que siguieron el protocolo de Observación de Aula del LETEGR2 en aulas de enseñanza de griego como segunda lengua en Grecia. Todos los datos generados se presentan teniendo en cuenta las diferentes etapas de observación en las que se han recogido (pre- y post-). La discusión de los datos se presenta a través de las voces de los dos grupos de participantes en referencia a los perfiles de los alumnos de una L2, el proceso de enseñanza y las prácticas de los docentes. Se intenta establecer un vínculo entre los comportamientos y las acciones observadas en ambos grupos de participantes y los conceptos teóricos subyacentes en el campo de la enseñanza y aprendizaje de una segunda lengua

The main features of issue and circulation of exchange bonds in the Russian Federation

The main features of stock exchange bonds were considered in the article, as well as the difference between stock exchange bonds and classical bonds. Two new types which appeared in the Russian federation in 2015-2016, such as single-day stock exchange bonds, and bonds issued within programs of exchange bonds. As the result, a conclusion was drawn on the future development of stock exchange bonds in Russian financial markets

Combined Approaches in Sialolithiasis of Major Salivary Glands

Combined (endoscopic-transcutaneous) techniques are an effective treatment for large and/or impacted stones of the major salivary glands. This approach results in high rates of symptom improvement and gland preservation. The complication rates are relatively low, further supporting the use of these techniques as an additional tool between the classic sialendoscopy and the external classic procedures of gland removal. In this chapter, we describe the combined approach for the parotid gland and the submandibular gland and finally, the retrograde sialendoscopy through the surgical field of an open approach