1,720,997 research outputs found
Colonic locomotion
No full textThe most effective screening method for colonic cancer is colonoscopy. However, colonoscopy cannot be easily embraced by the population because of the related pain intensity. Robotic devices that pull themselves forward through the colon are a possible alternative. The main challenge for such devices is their locomotion method along the slippery colon. This study focuses on devices which regularly switch between high friction to grip and low friction to slide and introduces a new method to manipulate friction by means of mucoadhesives. Mucoadhesives are polymers adhering to the mucus that covers the intestinal surface. We showed experimentally that mucoadhesive films can generate high static friction with the colon. In contrast with Coulomb friction, the static friction increases with the film area. The film geometry is of influence as well. Strikingly, when reducing the area by opening holes within the film structure, static friction can be considerably increased. A theoretical model was developed to express the frictional behaviour of mucoadhesive films. The role of geometry in the static friction offers new outlets to friction manipulation and provides new options for the design of the device. It seems also feasible to expand and apply the idea of increasing and manipulating friction by means of adhesive forces when gripping or handling soft, sensitive, or vulnerable objects. The artifice is to increase the adhesive forces up to a level that friction starts being controlled by adhesion, but without exceeding a ceiling of forces beyond which the adhesive falls into the area of permanent joints.Mechanical Maritime and Materials Engineerin
Expecting the unexpected: A study of interactive driving behaviour at intersections
No full textGiven the high number of encounters in traffic and the low number of accidents in which these result, it can be concluded that road users are quite good at interacting safely. To achieve a better understanding of this interactive behaviour, this thesis focused on road users' expectancies. In an explorative study, the aspects road users mention in their expectancies of interaction situations in traffic were studied. The mentioned aspects were distinguished into three categories: references to 1) right of way, 2) other road users and 3) the location of other road users (past, present and future). Subsequently, two experiments were conducted using linked driving simulators, which allowed for the study of interaction behaviour between two real people, rather than between a real and a pre-programmed road user. In the experiments, participants were confronted with expected and unexpected behaviour of a road user coming from an intersecting road. Additionally. in the second experiment, the interaction space was increased (by adjusting the infrastructure and providing information). The results showed that participants tended to take right of way when they were entitled to it, but also when they were confronted with another road user slowing down. Unexpected behaviour does not necessarily lead to a critically unsafe situation. The available interaction space is initially used to safely settle the interaction situation; additional interaction space is used to increase efficiency. It can be concluded that car drivers are quite capable of dealing with situations in which the behaviour of other car drivers is in conflict with the priority regulation if the interaction space allows for it.Trai
Development of Vessel Connectors for Coronary Bypass Surgery
No full textMechanical Maritime and Materials Engineerin
Advancing simulation-based driver training
No full textBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
A possible VTS-Operator Support System based on vessel traffic simulation
No full textIn this paper a possible Operator Support System (OSS) for vessel traffic management on the basis of vessel traffic simulation is presented. A proposal is made for a tool to give the Vessel Traffic Service (VTS) operator a better understanding in the development of vessel traffic situations and in advance identification of unsafe situations. An indication is given for the safety margins of the ships, indicating the reserves in control and space to cope with unexpected and unsafe situations. This information should enable the VTS-operator to manage and optimise the safety and efficiency of the future vessel traffic situations, without jeopardising the safety in the port of Rotterdam.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
Methods to improve situation awareness of an operator
No full textThis paper describes a new method to identify information overload problems in an alarm system. This method can also be used to become aware of the performance of an alarm system and to present the effectiveness of alarm rationalisation. Furthermore we show that pattern detection can be used to find meaningful patterns. Furthermore this paper describes the degree to which fault trees and pattem detection can contribute to a better situation awareness of an operator. It appears that fault trees are useful to improve the diagnosing capabilities of an operator.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
Model voor het genereren van realistische sleepbootassistentie
No full textThis report summarizes the result of a graduation project on the behaviour of a harbour tugmaster and his tug. First, research is described which has been conducted into the behaviour of a tugmaster. Based on this study a model has been developped to generate realistic tracks of a tugboat. This can be used to generate automatic tugboat assistence of a vessel simulated on a "Full Mission Bridge Simulator". The model is described in detail and simulation results are discussed. The results have been validated by expert judgement of tugmasters. It is concluded that the model generates realistic manoeuvres. It is capable of avoiding collisions with objects in its environment.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
Modeling Human Decision Making: A Cost-Benefit Interpretation for the Deviation of Safety Procedures
No full textHuman operators tend to make trade-offs when they are controlling complex systems. When an operator has the perception that a large increase in productivity can be obtained by safely getting round a safety provision, he is likely to do so. These so-called violations have led to several accidents in the last decades. The goals of this research are: (1) To identify the trade-offs made by operators, (2) to predict decisions based on these trade-offs and (3) to identify human characteristics which influence the individual decision making.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
CAB-SIM: A cause based operator model for use in dynamic Probabilistic Safety Assessments for nuclear power plants
No full textToday's technology enables people to build complex systems, such as nuclear power plants, that carry big hazards in them. Consequences of accidents that involve such plants can be severe. Hence, safety is an important issue in design and operation. The attention that has been given to system safety has resulted in an increase of component reliability. An accompanying effect is that in relatively more cases, the human operators contribute to accidental situations. Because of that, the study of the impact of operator behavior on system safety has received more attention during the last decade. One of the achievements that was made, is the development of the CAUse based Behavioral model (CAB model), as a part of the Human Interaction TimeLINE (HITLINE) methodology, which studies the impact of intentional operator behavior on system safety. The CAB model was designed to be used in Probabilistic Safety Assessments (PSAs). It uses knowledge about operating procedures, plant configuration and process behavior to perform a simplified simulation of cognitive processes, and to generate a set of possible operator actions with associated probabilities. To make the CAB model available for use in dynartiic PSA techniques, which include the systematic simulation of a large number of accident sequences, a computerized version of the CAB model, called CAuse based Behavioral SIMulator (CAB-SIM) was developed. The CAB model's mechanisms were translated into computer algorithms. Additionally, some improvements to the model were made. As a case study, the HITLINE methodology was applied to a hypothetical two tank system, using CAB-SIM. CAB-SIM was linked with HITline-SIMulator (HIT-SIM), a model for dynamic PSA, that was developed for this case study. The results of the simulations were incorporated in a simple PSA model of the system, that was developed for the purpose of demonstration. Additionally, CAB-SIM was incorporated in Accident Dynamic Simulator (ADS), an existing simulation model for dynamic PSA. The incorporation process included the coding of proper communication channels between CAB-SIM and ADS, modifying ADS simulation driving mechanism and its existing operator model, and the development of application-specific data, i.e. a system representation for use CAB-SIM. Some elementary results were generated. It is concluded that CAB-SIM is a model that seems to be able to improve the modeling of plant-operator interaction in dynamic PSA techniques, by analyzing the impact of intentional operator behavior on system safety. However, parts of the cognitive process simulation need further investigation; further, to make CAB-SIM applicable for real nuclear power plant PSAs, the quantification of operator errors, which currently contains many subjective elements, needs to be improved.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
Evaluatie van criteria voor het beoordelen van simulatieruns
No full textHet doel van deze afstudeeropdracht was om de in theoretische voorstudies voorgestelde veiligheidsindicatoren voor het beoordelen van simulatieruns te valideren met behulp van expertmeningen. Na observatie van simulatieruns en interviews met experts is gekozen om de Closest point of Approach (CPA) indicator en de Reserved Control Indicator (RCI) te valideren. Deze validatie is uitgevoerd door, voor een groot aantal runs, het verloop van de indicatorwaarden tijdens een run te vergelijken met een meting van de Mental Load met behulp van de Rating Scale Mental Effort enquête van Zijlstra. Uit de validatie van de indicatoren is gebleken dat, op basis van de gebruikte methode, geen duidelijke correlatie lijkt te bestaan tussen de expertbeoordeling (uitkomst RSME enquête) en de simulatordata (verloop indicator). Het verschillende stuurgedrag van de loodsen had invloed op het verloop van de indicatoren tijdens een run. Bovendien bleken de te beoordelen situaties te complex te zijn om door de indicatoren alleen te kunnen worden beoordeeld. In plaats van het beoordelen van een gehele run is daarom getracht een analyse uit te voeren van onderdelen van de run. Hiertoe is het intermitterende stuur-/ordergedrag van twee verschillende loodsen onderzocht. Op basis van het verloop van de versnelling van het schip bleek een gegeven order in te delen in een van de volgende drie controlmodes: orders voor koerscorrectie, orders voor windcorrectie en onduidelijke orders. Tevens leken de twee loodsen verschillende strategieën te hanteren bij het manoeuvreren van het schip. Als er in vervolgonderzoek beter inzicht verkregen kan worden in de frequentie, volgorde, aard en grootte van de orders, zou er een oordeel gevormd kunnen worden over het verloop van een simulatierun.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
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