Methodology for Definition of New Sectors for DP Assisted Offloading Operations in Spread Moored Platforms

2016 ◽  
Author(s):  
Ana Luisa de Barros Orsolini ◽  
Eduardo Aoun Tannuri ◽  
Felipe Santana Castelpoggi ◽  
Douglas Gustavo Takashi Yuba
Keyword(s):  
Risk Analysis ◽  
Static Analysis ◽  
Critical Conditions ◽  
Fast Time ◽  
Dynamic Simulations ◽  
Time Dynamic ◽  
Quantitative Analyses ◽  
Sector Angle ◽  
Definition Of ◽  
Real Time Simulations

This project defines a methodology for analyzing the proposition of expanding the operational sector of DP shuttle tankers in offloading operations in Spread Moored Platforms and still guaranteeing the operations’ safety. The methodology consists at first in an evaluation of the reduction of the operation’s downtime as a function of sector angle increase by performing static analysis. These simulations are calibrated and validated by performing fast time dynamic simulations. Then, a Preliminary Risk Analysis is made to assess the potential hazards associated with the operation on the new expanded sector and, if necessary, some quantitative analyses take place. Finally, the methodology proposes that real time simulations are performed so that most critical conditions are recreated in the presence of an experienced Captain so he can give his opinion on how safe the operation would be.

The Influence of Hold-Back Vessels on the Operation of a DP Drilling Rig: Control System and Stability Analysis

2017 ◽  
Author(s):  
Alex S. Huang ◽  
Eduardo Aoun Tannuri ◽  
Asdrubal N. Queiroz Filho ◽  
André S. S. Ianagui ◽  
Douglas G. T. Yuba ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Simplified Model ◽  
Fast Time ◽  
Dynamic Simulations ◽  
Positioning Systems ◽  
Time Dynamic ◽  
Drilling Rig ◽  
The Stability ◽  
Drilling Rigs

Certain maritime operations require the accurate positioning of the vessel, and in order to accomplish that DP (dynamic positioning) systems were developed. It combines the information obtained from sensors with the expected dynamic of the ship to better estimate its actual position and the external forces, and with those information the controller allocates the forces among the available actuators so the vessel keeps a desired position. In situations where drift of the vessel could cause great harm (human, material or environmental losses) it might be necessary to provide additional safeguards. One possible solution is to connect an AHTS (anchor handling tug supply) to the original DP vessel, in order to complement the forces generated by its thrusters. However as shown by Jensen (2008) and IMCA M 185 (2012), this connection could actually degrade the position keeping ability of the vessel, nullifying the purpose of improving the safety of the operation. The objective of the present paper is to confirm the hypothesis that the use of hold-back vessels to support DP drilling rigs may degrade the performance of the DP system, causing dynamic instability, and to determine the boundaries of operation under which this phenomenon occurs: sea state, parameters of the vessels and force transmitted by the hold-back vessel. Firstly, an analytical study of the system was done. It was considered a simplified model of two vessels connected by a cable with two degrees of freedom (one for each vessel), since the force applied by a cable is unidirectional. Using control theory, the limiting stiffness of the cable was determined by analyzing the poles of the system. Considering a catenary model for the connecting cable, it was possible to determine the maximum force that could be transmitted between the vessels without the system becoming unstable. The influence of the Kalman Filter in the stability of the system was also studied. Those results were then compared and confirmed with fast time dynamic simulations of the system, in which the influence of different environmental conditions were also added to the analysis. To complete the study, real time simulations were done on a full mission simulator, equipped with the original Kongsberg DP system for the drilling rig. The simplified model showed consistent results, validated by the simulations, demonstrating it can be a useful tool when analyzing the stability of two connected vessels.

scholarly journals Robust Output Synchronization of Arrays of Chaotic Sprott Circuits

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Ernesto V. Gonzalez Solis ◽  
David I. Rosas Almeida
Keyword(s):  
Parametric Uncertainties ◽  
Electronic Components ◽  
Closed Loop System ◽  
Pass Filter ◽  
Low Pass Filter ◽  
State Variable ◽  
Output Synchronization ◽  
Low Pass ◽  
Definition Of ◽  
Real Time Simulations

This article presents a technique for synchronizing arrays of a class of chaotic systems known as Sprott circuits. This technique can be applied to different topologies and is robust to parametric uncertainties caused by tolerances in the electronic components. The design of coupling signals is based on the definition of a set of functionals which depend on the errors between the outputs of the nodes and the errors between the output of a reference system and the outputs of the nodes. When there are no parametric uncertainties, we establish a criterion to design the coupling signals using only one state variable of each system. When the parametric uncertainties are present, we add a robust observer and a low pass filter to estimate the perturbation terms, which are subsequently compensated through the coupling signals, resulting in a robust closed loop system. The performance of the synchronization technique is illustrated by real-time simulations.

RTCONTACT: An Efficient Wheel-Rail Contact Algorithm for Real-Time Dynamic Simulations

2012 ◽  
Author(s):  
N. Bosso ◽  
A. Gugliotta ◽  
N. Zampieri
Keyword(s):  
Real Time ◽  
Computational Efficiency ◽  
Simulation Models ◽  
Experimental Tests ◽  
Contact Forces ◽  
Dynamic Simulations ◽  
Time Dynamic ◽  
Contact Algorithm ◽  
Complex Simulation ◽  
Precise Representation

Determination of contact forces exchanged between wheel and rail is one of the most important topics in railway dynamics. Recent studies are oriented to improve the existing contact methods in terms of computational efficiency on one side and on the other side to develop more complex and precise representation of the contact problem. This work shows some new results of the contact code developed at Politecnico di Torino identified as RTCONTACT; this code, which is an improvement of the CONPOL algorithm, is the result of long term activities, early versions were used in conjunction with MBS codes or in Matlab® environment to simulate vehicle behaviour. The code has been improved also using experimental tests performed on a scaled roller-rig. More recently the contact model was improved in order to obtain a higher computational efficiency that is a required for the use inside of a Real Time process. Benefit of a Real Time contact algorithm is the possibility to use complex simulation models in diagnostic or control systems in order to improve their performances. This work shows several comparisons of the RTCONTACT contact code respect commercial codes, standards and benchmark results.

scholarly journals Adjustment of Maintenance Approach for Improved Operability and Safety of Ship Navigation

2012 ◽  
Vol 22 (2) ◽  
pp. 95-103
Author(s):  
Ante Bukša ◽  
Ivica Šegulja ◽  
Vinko Tomas
Keyword(s):  
Risk Analysis ◽  
Lower Risk ◽  
Risk Index ◽  
Exhaust Valve ◽  
Maintenance Policy ◽  
Proposed Model ◽  
Risk Criterion ◽  
Ship Navigation ◽  
Definition Of ◽  
Navigation Safety

By adjusting the maintenance approach towards the significant components of ship’s engines and equipment, through the use of operational data from the ship machinery’s daily reports, higher operability and navigation safety can be achieved. The proposed maintenance adjustment model consists of an operation data analysis and risk analysis. The risk analysis comprises the definition of the upper and the lower risk criterion, as well as the definition of a risk index. If the risk index is higher than the lower risk criterion, the component is significant, while it is not significant and has an acceptable risk index if the risk index is lower than the lower risk criterion. For each significant component with a risk index found to be “unacceptable” or “undesirable”, an efficient maintenance policy needs to be adopted. The assessment of the proposed model is based on data regarding the power engine original operation throughout a 13-year period. The results of engine failure examinations reveal that the exhaust valve is the most vulnerable component with the highest rate of failure. For this reason the proposed model of adjusting the maintenance approach has been tested on the exhaust valve sample. It is suggested that the efforts to achieve higher ship operability and navigation safety should go in the direction of periodical adjustments of the maintenance approach i.e. choosing an efficient maintenance policy by reducing the risk indices of the significant engine components. KEY WORDS: maintenance adjustment approach, risk analysis, risk index, lower risk criterion, upper risk criterion, significant components, ship navigation

Study of Air Inclusion in Lubrication System of CVT Gearbox Transmission With Biphasic CFD Simulation

2016 ◽  
Author(s):  
Cristian Ferrari ◽  
Pietro Marani
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Critical Conditions ◽  
Positive Pressure ◽  
Computational Domain ◽  
Lubrication System ◽  
Operation Condition ◽  
Dynamic Simulations ◽  
Lubrication Performance ◽  
Lumped Element Model

The focus of this paper is the biphasic phenomena that occurs in a lubrication system of a CVT gearbox transmission of an agricultural tractor, in particular a Method of Analysis is outlined with the aim of mapping and assessing the behavior of the lubrication circuit. The study of the lubrication in gearboxes is an important issue in the design of off-road machines because their reliability depends mostly on the lubrication performance, as well as the machine’s lifetime and overall energy efficiency of the transmission is strongly dependent on the lubrication system behavior. In fact the role of the lubrication system is twofold: firstly to remove the heat generated in the highly loaded rolling bearings and the gears found in the power and accessory gearboxes via heat exchangers; secondly to lubricate these parts. The trend in the development of gearbox transmissions has been towards lower consumption and higher power transmitted, consequently it is necessary to conceive more effective and efficient lubrication systems. Nonetheless the lubrication problem often relies on a trial and error approach and most available scientific literature is based on lumped element model dynamic simulation or one phase thermo-fluid dynamic simulations, overlooking the effects linked to cavitation and air inclusion. One important phenomenon in lubrication systems is that of air suction. This can be seen in particular at high rotational speeds of shafts when the centrifugal force causes a positive pressure drop between inner lubrication pipes and outer radial conduits. In this case the air occupies part of the lubrication conduits, and since the domain is shared by the outflowing liquid phase and the air included, the monophase CFD simulation fails to predict the correct lubrication flow. If this effect is not carefully considered it could cause a lubrication unbalance among the various parts of the gearbox, creating a risk of transmission damage. In this paper the methodology will be presented step by step until in final a complete map of operation condition is created. A preliminary analysis of the circuitry is an essential phase of the project since the tractor’s transmission is an extremely complex assembly composed by hundreds of components therefore the lubrication circuit appears as a large net of moving hydraulic connections and consumers. From this analysis a computational domain is obtained and appropriately meshed. After the pivotal choice of the proper turbulence model and boundary conditions, various runs at different rotating speeds corresponding to the different operating ranges will be performed. The result will be contextualized by commenting on the fluid dynamics phenomena involved and the influence parameters on flow rate distribution, finally evaluating the performances of the lubrication circuit, and in particular highlighting the most critical conditions in terms of speed condition and locating the most critical gearbox parts.

Impact Dynamics of Single-Layered Graphene Sheets in Multibody Framework Using Nonlocal-Based-ANCF Modeling

2019 ◽  
Vol 19 (09) ◽  
pp. 1950099
Author(s):  
Qingtao Wang ◽  
Yang Zhang ◽  
Qixin Zhu ◽  
Zhaojun Pang
Keyword(s):  
Pair Potential ◽  
Gold Atom ◽  
Nonlocal Elasticity Theory ◽  
Nonlocal Theory ◽  
Impact Dynamics ◽  
Graphene Sheets ◽  
Dynamic Simulations ◽  
Definition Of ◽  
Vdw Force ◽  
The Impact

A new nonlinear model based on the absolute nodal coordinate formulation (ANCF) and the nonlocal elasticity theory is proposed to investigate the single-layered graphene sheets (SLGSs) impacted by nanoparticles. The geometrical definition of SLGSs is described by using the ANCF thin plate element, and the strain energy is expressed by using the nonlocal theory. The Lennard–Jones pair potential is adopted to model the van der Waals (vdW) force between SLGSs and nanoparticles. The impact dynamics of the system is simulated in multibody framework by using the generalized-alpha numerical integration method. The impact response of the gold atom–SLGSs system is simulated to validate the performance of the proposed model. Three impact dynamic simulations are conducted to investigate the influence of nanoparticles on the impact dynamics of SLGSs. The results show that the coupling of SLGSs vibration and vdW force led to the amplitude inconsistence of [Formula: see text]-position for nanoparticles.

A new definition of complexity in a risk analysis setting

2018 ◽  
Vol 171 ◽  
pp. 169-173 ◽  
Author(s):  
Anders Jensen ◽  
Terje Aven
Keyword(s):  
Risk Analysis ◽  
Definition Of

Technique of Code Obfuscation Based on Class Splitting

2012 ◽  
Vol 271-272 ◽  
pp. 636-640
Author(s):  
Yong Yong Sun ◽  
Guang Qiu Huang
Keyword(s):  
Reverse Engineering ◽  
Static Analysis ◽  
Object Oriented ◽  
Class Structure ◽  
Software Protection ◽  
Sensitive Data ◽  
Code Obfuscation ◽  
Engineering Software ◽  
Definition Of

The security of software is threatened by piracy, tampering and reverse engineering. Attackers attempt to get important algorithms and sensitive data of software by static analysis or reverse engineering. Software protection becomes an important problem. The algorithm of code obfuscation based on class splitting is proposed that uses of obfuscation technology. The definition of class splitting and realization on algorithm are described. At the same time, the performance on algorithm is analyzed. The obfuscation method enhances the degree of complication about program and static analysis becomes more difficult. The algorithm is applicable to object-oriented program with class structure.

scholarly journals FROM ADAM SMITH TO AMARTYA SEN: GLOBAL MARKET AS A POSSIBLE INSTRUMENT TO PROMOTE SOCIO-ECONOMIC DEVELOPMENT

2013 ◽  
Vol 70 (278) ◽  
Author(s):  
Carmen Pagliari ◽  
Edgardo Bucciarelli ◽  
Michele Alessi
Keyword(s):  
Economic Development ◽  
Adam Smith ◽  
Division Of Labour ◽  
Global Market ◽  
Moral Thought ◽  
Common Ethic ◽  
Socio Economic Development ◽  
Quantitative Analyses ◽  
International Laws ◽  
Definition Of

The present paper is aimed both at analyzing how Amartya Sen’s economic and moral thought is influenced by Adam Smith’s works and at offering a perspective on global market which could be investigated through quantitative analyses. In order to achievethis purpose, the authors provide a potential definition of globalization which arises not from empirical evidences but from the analysis of the links existing betwee Adam Smith’s thought and Amartya Sen’s one. Globalization is here considered firstas a global division of labour, second as a global market where the products generated by the division of labour are exchanged, and third as a complex socio-economic phenomenon which generates positive outcomes under two conditions: on one hand, every agent has to respect the rules coming from a common ethic, and, on the otherhand, countries and International Organizations have to guarantee that every agent respects national and international laws. Therefore, the perspective on globalization here presented shows how global market could be a potential instrument to promote socio-economic development.

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