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The Hurst Exponent as an Indicator of the behaviour of a Model Monopile in an Ocean Wave Testing Basin

Journal of Physics: conference Series 2015年第1期628卷

作者： Vikram Pakrashi Richard O'Shea Vesna Jaksic Jimmy Murphy Dynamical Systems and Risk Laboratory Civil and Environmental Engineering School of Engineering University College Cork Ireland Beaufort Environmental Research Institute University College Cork Ireland

With the importance of renewable energy well-established worldwide, and targets of such energy quantified in many cases, there exists a considerable interest in the assessment of wind and wave devices. While the individual components of these devices are often relatively well understood and the aspects of energy generation well researched, there seems to be a gap in the understanding of these devices as a whole and especially in the field of their dynamic responses under operational conditions. The mathematical modelling and estimation of their dynamic responses are more evolved but research directed towards testing of these devices still requires significant attention. Model-free indicators of the dynamic responses of these devices are important since it reflects the as-deployed behaviour of the devices when the exposure conditions are scaled reasonably correctly, along with the structural dimensions. This paper demonstrates how the Hurst exponent of the dynamic responses of a monopile exposed to different exposure conditions in an ocean wave basin can be used as a model-free indicator of various responses. The scaled model is exposed to Froude scaled waves and tested under different exposure conditions. The analysis and interpretation is carried out in a model-free and output-only environment, with only some preliminary ideas regarding the input of the system. The analysis indicates how the Hurst exponent can be an interesting descriptor to compare and contrast various scenarios of dynamic response conditions.

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Safety properties modelling

Safety properties modelling

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conference on human System Interactions, HSI

作者： Tullio J. Tanzi Raoul Textoris Ludovic Apvrille TELECOM ParisTech Paris ÃŽle-de-France FR L'Oréal Clichy Paris - France

In critical applications regarding safety, a solution must be validated before it is applied on the field. It is forbidden to test solutions directly on the real system for safety reasons. Any attempt of modification or introduction of a safety system must be approached with the utmost care. The proposed solutions must be validated, and, if possible, formally validated. It is the case of prevention systems for accidents, installed on highways. They also are in charge of gathering information in the case of an accident actually occurring. In this context, we aim to provide an approach to validate the behaviour of a critical system before its effective realisation. The system is modelled by a combination of agents spread around the world and working together in real-time. The agents' behaviour is modelled via an UML SysML model. Thanks to the tools available in the TTool environment and the ones developed only for this purpose, we can animate those agents and confirm, or not, their behaviour on various test situations (applications' rapid prototyping). Since the tests are not covering all the possibilities, we move to, then, verify formally the critical properties. This formal analysis is made possible by the mathematical grounds of the tool we use. The analysed properties are mainly safety properties; results regarding performance results are available as well.

关键词： Unified modeling language Safety Avatars Security Reliability Microwave ovens

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A new method for studying activity and reaction kinetics of photocatalytic water oxidation systems using a bubbling reactor

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CHEMICAL engineering JOURNAL 2014年 238卷 17-26页

作者： Hernandez, Simelys Bensaid, Samir Armandi, Marco Sacco, Adriano Chiodoni, Angelica Bonelli, Barbara Garrone, Edoardo Pirri, C. Fabrizio Saracco, Guido Ist Italiano Tecnol Ctr Space Human Robot POLITO I-10129 Turin Italy Politecn Torino Appl Sci & Technol Dept I-10129 Turin Italy

A novel method is proposed for studying kinetics and overall activity of water oxidation (WO) catalysts using a bubbling reactor, where oxygen concentration is measured simultaneously in the liquid and in the gaseous phase. Total oxygen evolution is obtained from direct integration. The actual rate of oxygen formation as a function of time, R-o2 (t) not accessible to direct measurement with batch reactors, is calculated from raw data through a simple but comprehensive mathematical model, taking into account mass transfer phenomena occurring in the system. Data concerning the activity of a nanostructured Co3O4 catalyst dispersed on a mesoporous silica (MSU-H), in the presence of tris(2,2'-bipyridyl)Ruthenium [Ru(bpy)(3)](2-) as sensitizer and Na2S2O8 as sacrificial reactant, are used to illustrate data processing. behaviour of the system is complicated by the occurrence, besides WO reaction, of the degradation of the sensitizer. Increase of sweeping gas flow increases R-o2 (t), by decreasing diffusional limitations to the reactions in the system: conditions for minimizing those were established. Data reported show that the assumption generally made of equilibrium between gaseous and liquid phase through Henry's law is incorrect, the more so the smaller the apparent mass transfer coefficient, k(L)a. An additional reason for removing oxygen from the liquid phase through bubbling is the occurrence of a parasitic reaction of molecular oxygen with the sensitizer. The method seems to yield reliable values of both IcLa and the set of R-o2 (t) values: the former scales with the flow of sweeping gas, as expected;R-o2 (t) curves are in qualitative agreement with accepted reaction mechanisms. Results concerning R-o2 (t) lend support to our previous kinetic studies (M. Armandi et al., ACS Catal, 2013, 3, 1272) where the reaction rate was assumed as constant for the first similar to 15 min. Availability of R-o2 (t) data not too biased by diffusional limitations opens the way to r

关键词： Artificial photosynthesis Water oxidation Bubbling reactor Photocatalysis Kinetic study

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Physical and numerical modelling of wire drawing process of Mg alloys in heated dies accounting for recrystallization 15

Physical and numerical modelling of wire drawing process of ...

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15th International conference on Metal Forming 2014

作者： Milenin, Andrij Kustra, Piotr Pietrzyk, Maciej AGH University of Science and Technology Mickiewicza 30Av. Kraków30-059 Poland

ISBN: (纸本)9783038351931

Magnesium-calcium alloys with increased bio-compatibility are applied in medicine for sake of high compatibility and solubility in human body. Production of surgical threads to integration of tissue may be one of the applications of those types of alloys. A new manufacturing process of thin wires made of biocompatible Mg alloys, including drawing in heated dies, was developed in Authors previous works. Conducting drawing process in conditions, in which recrystallization occurs, is the basis of the process. This allows for multi-pass drawing without intermediate annealing. Control of recrystallization after every pass using experimental method is complex so numerical simulation seems to be a rational method to design the process parameters. The purpose of the paper is developing a mathematical model of recrystallization for MgCa08 alloy, its implementation into the finite element (FE) code that simulates wire drawing and experimental verification of the numerical calculations. The first part of work was focused on the development of mathematical model of wire drawing process of Mg alloys in heated die. Proposed model takes into account thermal phenomena in the wire and in the die, plastic flow of the material, stress-strain state and recrystallization. The fracture criterion was implemented into FE code to eliminate the possibility of damage. The second part of the work was focused on experiments including upsetting and tensile tests for calibration of recrystallization and fracture models. Recrystallization model was calibrated on the basis of flow curves only what is a limitation. Therefore, experimental wire drawing on drawing bench developed by the Authors was the final stage of the work performed to validate the model. Recrystallization during wire drawing was studied. The developed computer program enables prediction of the recrystallization kinetics during wire drawing in heated die for MgCa08 alloy. The model of static and dynamic recrystallization of this al

关键词： Magnesium alloys

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Unsupervised Trajectory modelling using Temporal Information via Minimal Paths

Unsupervised Trajectory Modelling using Temporal Information...

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IEEE conference on Computer Vision and Pattern Recognition

作者： B. Cancela A. Iglesias M. Ortega M. G. Penedo VARPA Group Universidade da Coruna

ISBN: (纸本)9781479951192

This paper presents a novel methodology for modelling pedestrian trajectories over a scene, based in the hypothesis that, when people try to reach a destination, they use the path that takes less time, taking into account environmental information like the type of terrain or what other people did before. Thus, a minimal path approach can be used to model human trajectory behaviour. We develop a modified Fast Marching Method that allows us to include both velocity and orientation in the Front Propagation Approach, without increasing its computational complexity. Combining all the information, we create a time surface that shows the time a target need to reach any given position in the scene. We also create different metrics in order to compare the time surface against the real behaviour. Experimental results over a public dataset prove the initial hypothesis' correctness.

关键词： Trajectory Computational modeling Measurement Equations mathematical model Density functional theory Computer vision

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modelling of lightning current in the case of striking to a tall structure

Modelling of lightning current in the case of striking to a ...

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International Power engineering and Optimization conference (PEOCO)

作者： N. Rameli M. Z. A AbKadir M. Izadi C. Gomes N. Azis N. Abd Rahim S. N. M Arshad Centre for Electromagnetic and Lightning Protection Research (CELP) Universiti Putra Malaysia Malaysia

Lightning current is an important parameter that has to be considered. The different behaviour of lightning current depends on the way the lightning strikes either as a direct or indirect lightning strike. In this paper the modelling of the current as a result of a direct strike of lightning on a tall structure is considered. A few of up-to-date on current models, current functions, reflection factors, the return stroke velocity (RSV), the general equation representation of this case are reviewed. Also, through MATLAB software, the results of a case study are generated. The results show a good agreement with the measured values. In addition, the behaviour of the lightning current is evaluated at different heights of the lightning channel with respect to the top and bottom of a tall structure. Also, the lightning current at the top and bottom of the tall structure are observed for different values of the reflection factor. The results show that the peak of the lightning current along different heights of the channel with respect to the top and bottom of a tall structure decreases with increasing height of the channel. Also there is a time delay during the initial time period. Furthermore, the lightning current at the bottom of a tall structure has a high value of peak current and has an attenuation wave shape of current that compares with the lightning current at the top of the tall structure. As a result, this paper may provide benefit in evaluating the electromagnetic (EM) field since the behaviour of the lightning current on a tall structure is known.

关键词： Lightning Poles and towers Reflection mathematical model Equations Current measurement conferences

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Characteristics of human Arm Impedances: A Study on Daily Movement

Characteristics of Human Arm Impedances: A Study on Daily Mo...

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International conference on Computer Modeling and Simulation, UKSIM

作者： Tasnuva Tabashhum Choudhury Md Mozasser Rahman Md Raisuddin Khan Dept. of Mechatronics Engineering IIUM Malaysia

This paper presents the impedance characteristics of human arm in daily spatial activity. human arm is considered as a mass-spring-damper system. The input data in the form of Cartesian position is measured to get dynamic impedance relationship by the motion equation for the mass-spring-damper system. Mappings are done by various combinations to observe the nature of the different impedance components during dynamic movement. The significant amount of variation in damping and inertia components are observed in every turning of the arm movement while the stiffness shows the changing behavior throughout the movement. From this study it is known that for this particular movement the arm follows a pattern and same behavior is followed for the repetitions of the movement. The obtained result could be beneficial for the study of upper extremity exoskeleton for human rehabilitation.

关键词： Impedance Impedance measurement mathematical model Dynamics Equations Damping Wrist

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Fabrication and modelling of segway

Fabrication and modelling of segway

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IEEE International conference on Mechatronics and Automation

作者： Muhammad Harris Khan Mehak Chaudhry Taimoor Tariq Qurat-ul-Ain Fatima Umer Izhar Department of Mechatronics Engineering National University of Science and Technology

The paper presents the design of a fully functional self balancing vehicle capable of bearing the human load using the principle of dynamic stability. Requirement of the venture includes designing and fabrication of Segway and BLDC motor controller, modeling of the system and implementation of control for stabilization. Indigenous electronic circuitry, accelerometer and BLDC motor controller are used in the system. 500 Watt power motor makes this Segway capable of bearing the human load. It includes static and dynamic analysis of Segway on ANSYS, designing of BLDC Motor controller, mathematical modeling of the system and designing of the PID controller using Root Locus Analysis and implementation on Segway.

关键词： Stress DC motors Transfer functions mathematical model Force Equations Vehicles

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Prediction of Jet Engine Parameters for Control Design Using Genetic Programming

Prediction of Jet Engine Parameters for Control Design Using...

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International conference on Computer Modeling and Simulation, UKSIM

作者： Giovanna Martínez Arellano Richard Cant Lars Nolle School of Science and Technology Nottingham Trent University Nottingham U.K. Department of Engineering Sciences Jade Hochschule/University of Applied Science Wilhelmshaven Germany

The simulation of a jet engine behavior is widely used in many different aspects of the engine development and maintenance. Achieving high quality jet engine control systems requires the iterative use of these simulations to virtually test the performance of the engine avoiding any possible damage on the real engine. Jet engine simulations involve the use of mathematical models which are complex and may not always be available. This paper introduces an approach based on Genetic Programming (GP) to model different parameters of a small engine for control design such as the Exhaust Gas Temperature (EGT). The GP approach has no knowledge of the characteristics of the engine. Instead, the model is found by the evolution of models based on past measurements of parameters such as the pump voltage. Once the model is obtained, it is used to predict the behaviour of the jet engine one step ahead. The proposed approach is successfully applied for the simulation of a Behotec j66 jet engine and the results are presented.

关键词： mathematical model Predictive models Jet engines Training Sociology Statistics

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Balancing Control of Robot Gymnast Based on Discrete-Time Linear Quadratic Regulator Technique

Balancing Control of Robot Gymnast Based on Discrete-Time Li...

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International conference on Artificial Intelligence, modelling and Simulation (AIMS)

作者： H.G. Kamil E.E. Eldukhri M.S. Packianather University of Karbala Karbala Iraq Institute of Mechanical and Manufacturing Engineering Cardiff University Cardiff UK

The most important purpose of this paper is to stablise and balance a robot gymnast (Robogymnast) upside down. The Robogymnast is a complex non-linear triple inverted pendulum system. Robogymnast attached to a freely rotating high bar mounted on ball bearings. It mimics the human acrobat, consists of three links and three joints, first joint is passive (unpowered joint) and the rest are active (powered joint). The passive join represents a great challenge to balancing the robot at the upright position. In order to achieve the required performance, the optimal control theory was used. The discrete-time linear quadratic regulator (DLQR) controller was carried out using the linearized mathematical model of the plant which was used to calculate the state feedback control law. Apart from this, the choice of weighting matrices of the DLQR was discussed. The results showed successful stablising and balancing of Robogymnast.

关键词： Joints mathematical model Robots Eigenvalues and eigenfunctions Regulators Optimal control

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