Murat Ozkok

A fuzzy based assessment method for comparison of ship launching methods

In a shipyard production system, launching operation is vital process since launching stage is time consuming process as well as being high cost. Therefore, this is a significant issue for shipyards. Choosing the most appropriate one among launching methods gives an advantage to shipyards to obtain competitive power against their competitors. If this is done, shipyards can commit to delivery of more ships and make more profit. In this study, launching methods are evaluated in terms of various performance criteria by means of an integrated method including Analytic Hierarchy Process AHP, Fuzzy Information Axiom FIA, Technique for Order Performance by Similarity to Ideal Solution TOPSIS, and Strengths, Weaknesses, Opportunities, and Threats SWOT analyses. Then, the dry docking technique was determined as the most convenient launching method with respect to the conflicting criteria.

Evaluation of shipyard selection criteria for shipowners using a fuzzy technique

There are various stages to the process of acquiring a vessel. First, a decision must be made on what vessel is needed. Next, an appropriate shipyard is selected; this decision is very significant, as it will determine the workmanship quality and delivery date of the vessel to be manufactured. From the point of view of a shipowner, receiving the vessel on time and manufactured to specification is crucial. From the point of view of the shipyard, it is vital to take as many orders as possible; therefore, one of the highest priorities of shipyards is to be the first choice for as many shipowners as possible in order to increase their requirement for steel fabrication and consequently their profits. In this study, the shipyard selection criteria for shipowners are presented and the degree of importance of each criterion is determined using a fuzzy analytic hierarchy process (AHP) technique. The aim of the study is to provide shipyards with information about the perspective of shipowners with regard to the shipyard selection process, thus allowing shipyards to strengthen their weaknesses and increase the number of shipowners which choose them to manufacture their ships.

Prediction of main particulars of a chemical tanker at preliminary ship design using artificial neural network

ABSTRACT Preliminary ship design is an important part of the ship design and a reliable design tool is needed for this stage. The aim of this study was to develop an artificial neural network (ANN) model to predict main particulars of a chemical tanker at preliminary design stage. Deadweight and vessel speed were used as the input layer; and length overall, length between perpendiculars, breadth, draught and freeboard were used as the output layer. The back-propagation learning algorithm with two different variants was used in the network. After training the ANN, the average of mean absolute percentage error value was obtained 4.552%. It is also observed that the correlation coefficients obtained were 0.99921, 0.99775, 0.99537 and 0.9984 for training, validation, test and all data-sets, respectively. The results showed that initial main particulars of chemical tankers are determined within high accuracy levels as compared to the sample ship data.

Determination of the Effects of the Pre-Outfitting and Pre-Piping Assembly Operations on Shipyard Productivity

Abstract The process improvement operations are very significant in shipbuilding industry as the other industries. In recent years, the shipyards attempt to improve their processes by examining their current production system and to reduce the cycle time of the interim product so that they can keep their competitive power. If the cycle time of the interim products is decrease, that may cause to increase the annual production capacity and market share of the shipyard. In order to do this, the shipyards have to analyse their own production system and carry out some improvements on it. In this study, the effects of carrying out the outfitting and piping assembly operations in earlier work stations were investigated by using a methodology presented here. The steps in the methodology were applied to a double bottom block of a container ship. It was shown that if the outfitting and the piping assembly operations are carried out in earlier stations instead of the block assembly station, this may increase the throughput by 33%. The results of the study were discussed in the final section.

The effects of matrix module structure on shipyard panel line's throughput

ABSTRACT Over the last decades a really tough competitive environment has been observed in shipbuilding sector. Under these circumstances shipyards desire to reduce product cycle time in order to manufacture the product as soon as possible. For this reason it is required to make some alterations in shipyard production system in order to reduce cycle time. In this study a panel fabrication line used in a shipyard, has been considered. The workstations of the panel line have been modeled by using ARENA simulation software and the effects of matrix module assembly on panel line throughput, have been determined

A Fuzzy Multiphase and Multicriteria Decision-Making Method for Cutting Technologies Used in Shipyards

Cutting operation is one of the most significant processes in shipbuilding. In the shipyard industry, there are various cutting technologies and the selection of the appropriate cutting technology for the production process is a serious engineering problem. The main aim of this study is to find out the most appropriate cutting technique for shipyard industry by considering conflicting factors such as cost, risk, and performance. An integrated method including fuzzy, analytic hierarchy process, information axiom, and technique for order performance by similarity to ideal solution has been utilized for the evaluation procedure. Oxy-fuel technology is determined as the most appropriate cutting technology for shipyard industry.