Stein Haugen

Surveillance and outcome of fetuses with gastroschisis

Infants with gastroschisis have a high survival rate. However, the rate (10–15%) of intrauterine fetal death (IUFD) is considerable, and the association with fetal distress is well known. The aim of this study was to describe the outcome of fetuses with a prenatal diagnosis of gastroschisis. The impact of correct prenatal diagnosis, surveillance and signs of complicating risk factors were evaluated.

Characteristics and outcome of 90 cases of fetal omphalocele

The aim of this study was to describe the outcome of a case series of fetuses with omphalocele.

Esophageal obstruction-prenatal detection rate and outcome.

Prenatal diagnosis of esophageal obstruction is believed to improve the outcome for the affected newborn. However, the prenatal detection rate is only 10–40%, the diagnosis is usually not made before the third trimester and the false‐positive rate has been high. This study investigated the prenatal detection rate and time of prenatal diagnosis at our center and its influence on outcome. In addition, incidence, detection rate and accuracy of the diagnosis in a large non‐selected population were determined.

Imperforate anus: a relatively common anomaly rarely diagnosed prenatally

Despite the relatively common occurrence of imperforate anus, prenatal diagnosis is rarely reported. In this study, we investigated the presence and diagnosis of imperforate anus along with strategies for improving prenatal diagnosis of the condition.

Perspectives on risk and the unforeseen

Black swans have been discussed lately. Some recent contributions to the understanding of black swans have been provided by Aven [1] and Aven and Krohn [3]. It is important to be aware of events which may come as complete surprise, which creates uncertainty in the risk assessment. This is consistent with the proposed revision of the definition of risk by Petroleum Safety Authority (PSA) [Norway]. But we should at the same time also try to look beyond this and see how we can use this concept to avoid serious accidents or at least reduce the consequences should accidents occur. In this paper we proposed to restrict the black swan concept to unknown unknowns. Cases illustrate how the wider definition may lead to misleading and unfortunate effects that will not lead to good risk management practices. The wider definitions proposed by Aven & Krohn are proposed to be counterproductive if seen in a risk management context.

Generalized methodology for operational risk analysis of offshore installations

The barrier and operational risk analysis (BORA) project has developed a model for risk analysis based on the use of event trees, fault trees, influence diagrams, and risk influencing factors (RIFs). The model has been applied in some case studies in the project. The experience from these case studies has been used to develop a generalized methodology for analysis of operational barriers that are intended to prevent hydrocarbon leaks. A stepwise description of this generalized methodology is presented and discussed in the paper.

Complex accident scenarios modelled and analysed by Stochastic Petri Nets

Abstract This paper is focused on the usage of Petri nets for an effective modelling and simulation of complicated accident scenarios, where an order of events can vary and some events may occur anywhere in an event chain. These cases are hardly manageable by traditional methods as event trees – e.g. one pivotal event must be often inserted several times into one branch of the tree. Our approach is based on Stochastic Petri Nets with Predicates and Assertions and on an idea, which comes from the area of Programmable Logic Controllers: an accidental scenario is described as a net of interconnected blocks, which represent parts of the scenario. So the scenario is firstly divided into parts, which are then modelled by Petri nets. Every block can be easily interconnected with other blocks by input/output variables to create complex ones. In the presented approach, every event or a part of a scenario is modelled only once, independently on a number of its occurrences in the scenario. The final model is much more transparent then the corresponding event tree. The method is shown in two case studies, where the advanced one contains a dynamic behavior.

Analysis of Barriers in Marine Operations on Offshore Oil Installations

The project Risk Modeling – Integration of Organizational, Human and Technical factors is developing a model for quantifying barrier performance related to major risk hazards (OMT-model). The model combines knowledge relating to organizational, human and technical aspects, and is developed in close relationship between research centers, universities and offshore operators. The OMT-model has been tested for process leakages on onshore plants with good results. The same methodology has been used to identify the risk influence factors (RIF) — or Performance Shaping Factors — related to marine operations. One of the main risk contributors in a quantified risk analysis (QRA) is collision between FPSO and shuttle tanker and the method is used on this case. QRAs together with data from the yearly project “Trends in Risk Level” performed by the Petroleum Safety Authority in Norway, incident and accident investigations, operating procedures and expert judgment form the basis for identifying the RIFs and the results are summarized in this paper. By controlling the RIFs and accompanying identified root causes the probability and consequences of a hazard or accident will be largely reduced compared with the present situation.Copyright

Reliability analysis of the IMO regulation – safe return to port

The Safe Return to Port (SRtP) regulation requires physically separated redundancy for passenger ships to ensure the safe return of the ship after a casualty. Although complying with this regulation significantly increases shipbuilding time and cost, the quantitative effect of this regulation on system reliability is not well known. The main objective of this article is to investigate the SRtP regulation by reliability analysis methods and show the effect of this regulation through case studies. This article suggests reliability analysis methods for two different modes of ship system operation; continuous mode of operation and low-demand mode of operation. Location fault tree and a Markov model are suggested, respectively. Two case studies focusing on fire and flooding for each mode of operation demonstrate that applying the SRtP regulation increases the system reliability substantially.

Ship Trajectory Control Optimization in Anti-collision Maneuvering

A lot of attention is being paid to ship’s intelligent anti-collision by researchers. Several solutions have been introduced to find an optimum trajectory for ships, such as Game Theory, Genetic or Evolutionary Algorithms and so on. However, ship’s maneuverability should be taken into consideration before their real applications. This paper focuses on ship’s trajectory control problem in anti-collision maneuvering. At first, a simple linear ship maneuverability model is introduced to simulate its movement under different speed and rudder angle. After that, the ship’s trajectory control is studied by considering the duration of rudder, operation distance to turning points, and maximum angular velocity. The details for algorithm design are also introduced. By giving some restrictions according to the requirements from COLREGs, the intervals for rudder angle in different circumstances can be determined by the curves. The results can give very meaningful guidance for seafarers when making decisions.