1,720,954 research outputs found
Wear and Friction in a Controllable Pitch Propeller
No full textThe author is a naval architect and this book is his PhD thesis. In this research the author focuses on friction in a controllable pitch propeller (CPP), formation of wear in a CPP system, and their mutual dependence. Instead of going deeply only in tribology aspects, the author tries to get an overall description of the problem incorporating hydrodynamic and mechanical aspects of a CPP. By doing so, the author concludes that total wear is the result of several wear mechanisms but in the first place fretting and sliding wear. An attempt has been made to explain the existence of fretting as a consequence of too high oscillations in the wake speed when the ship is sailing in seaway. Wear experiments presented in this book show fretting wear to be more dangerous than other wear mechanisms in CPP. At the end, based on experiments and previous analysis, the author presents a total wear model for a CPP. This book is useful for marine engineers to better understand the properties and limits of a CPP in real service conditions. It further can be an example how to use a multi disciplinary approach in solving a specific problem. Also it can be useful for tribology experts to get an impression of the problems the marine people encounter and how these relate to their own expertise.Marine and Transport TechnologyMechanical, Maritime and Materials Engineerin
A battery’s heartbeat: How to estimate the state of health of an online battery by use of non-invasive measuring methods
No full textMechanical, Maritime and Materials EngineeringMarine and Transport Technolog
Sensor Fusion and Observer Design for Dynamic Positioning
No full textThe fusion of measurements from distributed sensors for dynamic positioning (DP) system based on state estimation algorithms is studied in this thesis in order to increase the accuracy and redundancy of the reference system in DP and a state observer is also designed to estimate of the low frequency vessel motion for the input of DP controller. Different filters such as lowpass filter, notch filter, Kalman filter (KF), extended Kalman filter (EKF), unscented Kalman filter (UKF) and square-root unscented Kalman filter (SRUKF) are introduced and discussed in this thesis. The square-root unscented Kalman filter is proposed for the fusion of measurements, wave filtering and state estimation based on kinematics while the Kalman filter is used as an observer for the estimation of the state vector of a vessel mathematical model for dynamic positioning operation. Thereafter a Matlab/Simulink based marine system simulator containing external environment, vessel model, reference sensors, sensor fusion system, observer and controller is built to test the algorithms of sensor fusion and observer designed in this thesis. The results of the simulation show that the errors of low frequency position and heading prediction are below 0.2m and 0.3 degree respectively which is accurate enough for DP operation. The dead reckoning starts automatically as soon as the reference system fails and the error of the dead reckoning increases gradually overtime. The position error in dead reckoning is about 5m after 1800s in simulation, which means the DP system is still able to estimate the position of the vessel without any position measurements in certain time, avoiding collision caused by the sudden position loss.Ship Design Production and OperationMaritime and Transport TechnologyMechanical, Maritime and Materials Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Ship diesel engine performance modelling with combined physical and machine learning approach
No full textCondition Based Maintenance on diesel engines can help to reduce maintenance load and better plan maintenance activities in order to support ships with reduced or no crew. Diesel engine performance models are required to predict engine performance parameters in order to identify emerging failures early on and to establish trends in performance reduction. In this paper, a novel approach is proposed to accurately predict engine temperatures during operational dynamic manoeuvring. In this hybrid modelling approach, the authors combine the mechanistic knowledge from physical diesel engine models with the statistic knowledge from engine measurements on a sound engine. This simulation study, using data collected from a Holland class patrol vessel, demonstrates that existing models cannot accurately predict measured temperatures during dynamic manoeuvring, and that the hybrid modelling approach outperforms a purely data driven approach by reducing the prediction error during a typical day of operation from 10% to 2%
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Two-part modelling format for modelling marine diesel engines in joules
No full textThe modelling approaches can go to two extremes: fully data-oriented and fully process oriented. Modelling for diesel engines is not excluded. Usually data-oriented is computational friendly and accurate and the latter is detail and flexible. A high-speed diesel engine model is missing in project JOULES. The objective of this work is to develop a generic diesel engine model and use it within JOULES so that it can fill in the vacancy of high speed diesel engine model as well as using for other engines. A two-part modelling format was proposed to provide flexibility and user-friendliness. Modifications including adding three sub-models, changing interface have been made to the DE A diesel model in order to satisfy the outputs requirement from JOULES, be converted into FMUs and fit into the two-part modelling format. A set of six versions of process part were achieved and the data part interface was determined. Sensitivity analysis was done to support the use of newly added sub-models. After validating all model versions, the mode was used in the case provided by Navantia. The results showed that the two-part modelling format is accurate enough for the work and extremely flexible. However, a long simulation time was recorded due to the use of FMUs.SDPOMarine & Transport TechnologyMechanical, Maritime and Materials Engineerin
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Improvements to the design process of the energy distribution system: A comparison between operational use of the energy distribution system of a naval ship and its expected use during the design phase
No full textAfter a ship is delivered from a shipyard to a customer, its operational use is not yet structurally compared to its expected use. This lack of structural comparison results in limited verification and self-evaluation of the design process. The objective of this research is therefore to develop a method to analyze operational data and apply this operational data analysis method to the Royal Netherlands Navy Holland class Oceangoing Patrol Vessels (OPVs). These vessels use Combined Diesel Electric or Diesel (CODELOD) propulsion. The data analysis focuses on the electrical energy distribution system, because this determines a large portion of the total fuel consumption of the ships. Operational data from these ships was collected from the Integrated Platform Management System, which is installed on the OPVs. By applying the operational data analysis on the Holland class OPVs, the generator plant setup is evaluated. Based on the results from this analysis, a father-son generator setup is proposed, consisting of two 835 ekW gensets and two 475 ekW gensets. This setup has better redundancy, less fuel consumption, and a lower total installed power, compared to the three currently installed 920 ekW generators. The proposed father-son altenative setup reduces the total installed electric power by 5.1%, and saves 0.4% to 2.4% fuel consumption for electricity generation. To obtain an accurate calculation of fuel consump tion for widely distributed power consumption profiles, a power consumption distribution must be used instead of an average value.Mechanical Engineering - Mechanical Systems and IntegrationSDOMechanical, Maritime and Materials Engineerin
- …
