Judging From Experience: Experienced Sequences are Predicted Better than Described Sequences

When attempting to predict future events, people commonly rely on historical data. Events in a time series can be experienced sequentially (dynamic mode), as in learning about decisions from experience (e.g., Kusev et al., in press, JEP:HPP), or, as with learning about decisions from descriptions, they can also be retrospectively viewed holistically (static mode) – not experienced individually in real time. In one experiment, we studied the influence of presentation mode (dynamic and static) on three sorts of judgments: (i) predictions of the next event (forecast), (ii) estimation of the average value of all the events in the presented series (average) and (iii) judged satisfaction of workers given that the series represented their monthly income (satisfaction). Relative to the static mode participants‘ responses in dynamic mode were anchored on more recent events for all three types of judgments but with different consequences – hence dynamic presentation improved prediction accuracy, but not estimation

An optimization model for the planning of offshore plug and abandonment campaigns

Plug and abandonment (P&A) operations can be time-consuming and thus very costly, especially for subsea fields. P&A of subsea wells require dedicated vessels such as high cost semi-submersible drilling rigs or lower cost Riserless Light Well Intervention vessels. This paper describes an optimization model that can be used to plan multi-well P&A campaigns by finding cost-efficient vessel routes and allocation of P&A operations to different rigs and vessels. The model's functionality is demonstrated on ten different synthetic cases, generated from realistic data. Results show that significant cost savings can be made by adapting the optimal solutions from this model compared to planning strategies that are currently used by operators, as well as by cooperating across fields and licenses in a large campaign.publishedVersio

Survey design and analysis procedures: a comprehensive review of good practice

This paper provides a major review of acoustic survey and-data analysis procedures, it has been prepared as a result of discussions in the FAST working group of ICES. A review of published literature is combined with an assessment of methodology. A consideration of information available a priori and its impact on the choice of survey area and survey design is presented. The subject of predetermined survey tracks using both systematic and random strategies is addressed, indicating the assumptions implied by these choices. Adaptive strategies that might be required for mobile or less predictable spatia1 distributions are discussed along with the advantages and the costs of an adaptive approach. The methods of determining of stock species composition are examined. The methods for assessing the degree of homogeneity species size and proportion are presented. The important choice of averaging method i.e. how the samples provide information on the true density within an area is examined. Sources of error within the estimate are discussed. Firstly, methods for computing the spatial sampling error are examined, and secondly, a summary of other sources of error is presented. A appraisal of these errors is presented and provides an intrinsic error analysis. Finally a brief comparison of the results of acoustic surveys with the results of other techniques is presented. Throughout the paper the assumptions implicit in each choice are discussed, and appropriate selections of survey design and analysis methods are presented in tabular form. The paper concludes with a summary of recommended procedures

APPLICATION OF A SPEED EXCLUSION ZONE ALGORITHM ON A LARGE 10MW OFFSHORE WIND TURBINE

ABSTRACT To optimize tower design it is desirable to relax the constraint of having to place natural frequencies outside the rotor and blade passing frequency-bands. A speed exclusion zone algorithm is tested to assess its effectiveness on preventing tower resonance caused by 3p thrust oscillations. The effect of the speed exclusion zone algorithm on power output is also considered. A simulation model adequate for qualitative testing of the algorithm is developed and implemented in the simulation tool Simulink by MathWorks. The model is based on a 10MW offshore wind turbine and includes a simplified representation of rotor aerodynamics, drive-train and generator dynamics and a twodimesional finite element representation of the tower and support structure. To support simulations a rotor speed controller is implemented together with wind models accounting for wind shear, tower shadow, turbulence and rotational sampling. A significant reduction in tower vibration is seen with a ±10% speed exclusion zone. A exclusion zone width of ±5% is shown to increase tower vibrations in some cases. The speed exclusion zone algorithm will lead to a reduction in power output for a ±10% and ±15% speed exclusion zone. For the ±5% speed exclusion zone no significant change in power output is observed

Modelling and analysis of offshore energy hubs

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OMAE2007-29172 DEEP WATER RISER COLLISION AVOIDANCE BY TOP TENSION CONTROL

ABSTRACT For tensioned riser arrays in deep waters interference between individual risers in strong ocean current is a key design and operational concern. The lateral deflections are likely to be large, and the risers may experience collision with fatigue or surface damage as a consequence. In this paper a system consisting of a tension leg platform (TLP), a pair of risers, environmental forces and hydrodynamic interaction is presented. The control system is described, and a set of control objectives with corresponding control strategies are suggested. The collision avoidance effects of the different control objectives are shown through simulations

Online wave estimation using vessel motion measurements

In this paper, a computationally efficient online sea state estimation algorithm is proposed for estimation of the onsite sea state. The algorithm finds the wave spectrum estimate from motion measurements in heave, roll and pitch by iteratively solving a set of linear equations. The main vessel parameters and motion transfer functions are required as input. Apart from this the method is signal-based, with no assumptions on the wave spectrum shape, and as a result it is computationally efficient. The algorithm is implemented in a dynamic positioning (DP) control system, and tested through simulations in different sea states, with heading changes. Discrete stability analysis is performed to find iteration gains in the algorithm