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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Environment & Safety
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Journal DOI :
The Korean Society of Marine Environment and safety
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Volume & Issues
Volume 3, Issue 2 - Jul 1997
Volume 3, Issue S1 - May 1997
Volume 3, Issue 1 - Jan 1997
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On the Visual Scene Validity of the Microcomputer Aided Port Design Simulator
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 1~12
One of the main uses for ship simulators is in the field of port design, and an increasing number of simulators, of varying degrees of fidelity, are being used for this purpose. An essential feature of all such simulators is their visual scene, which must be of sufficent fidelity to convey the key visual cues adequately. This paper examines the ability of a number of experienced mariners to perceive speeds and distances correctly using Computer Generated Imagery visual scenes of different fidelity, compared with their performance at sea. From the results, it was found that the microcomputer based simulator might be considered, as far as its visual scene representation is concerned, to be as valid as the full mission ship simulator for the port design task.
Effect of Laser Pulse Shaping on Reduction in Defects of Stainless Steel Sport Weld Metals
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 13~21
This paper describes the effectiveness of laser pulse shaping in eliminating weld defects such as porosity, cracks and undercuts in pulsed Nd:YAG Laser welding. A large porosity was formed in a keyhole mode of deep penetration weld metal of any stainless steel. Solidification cracks were present in Type 303 with about 0.3%s. The conditions for the formation of porosity were determined in further detail in Type 316. With the objectives of obtaining a fundamental knowledge of formation and prevention of weld defects, the fusion and solidification behavior of a molten puddle was observed during laser spot welding of Type 310S. through high speed video photographing technique. It was deduced that cellular dendrite tips grew rapidly from the bottom to the surface, and consequently residual liquid remained at the grain boundaries in wide regions and enhanced the solidification cracking susceptibility. Several laser pulse shapes were investigated and optimum pulse shapes were proposed for the reduction and prevention of porosity and solidification cracking.
Dynamic Bechavior of the keyhole in Laser Processing
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 23~31
The results of high speed photography, acoustic emission detection and plasma UV radiation intensity measurement during CO2 laser welding of stainless steel 304 are presented. Video images with high spatial and temporal resolution allowed to observe the melt dynamics and keyhole evolution. The existence of a high speed melt flow which originated from the part of weld pool and flowed along the sides wall of keyhole was confirmed by the slag motion on the weld pool. the characteristic frequencies of flow instability and keyhole fluctuations at different welding speed were measured and compared with the results of Fourier analyses of temporal acoustic emission (AE) and light emission (LE) spectra. The experimental results were compared with the newly developed numerical model of keyhole dynamics. (The model is based on the assumption that the propagation of front part of keyhole into material is due to the melt ejection driven by laser induced surface evaporation.) The calculations predict that a high speed melt flow is induced at the front part of keyhole when the sample travel speed exceeds several 10mm/s. The numerical analysis also shows the hump formation on the front keyhole wall surface. Experimentally observed melt behavior and transformation of the AE and LE spectra with variation of welding speed are qualitatively in good agreement with the model predictions.
A Study on Real Time Simulation of Harbour Manoeuvre and Its Application to Pusan Harbour
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 33~49
This paper deals with desktop simulator which can be utilized for total assessment of safety in harbour manoeuvre on a personal computer. Current, wind and tug forces are treated as well as precise mathematical model of a ship for low advance speed including stopping behaviour with effect of water depth. By using the desktop simulator, the real time simulation of berthing and unberthing manoeuvres was applied to Pusan harbour as an example. It is concluded that the above simulation technique will be beneficial to assessment of ship's safety under the environmental conditions is harbour area.
The Characteristics of Water Quality in Mokpo Harbour(II) -Centering on eutrophication in summer-
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 51~61
The in situ observations and the seawater analyses were conducted in July and Auguse, 1996 for the purpose of evaluating the characteristics of seawater quality centered about eutrophication in Mokpo harbour. By applying the OECD standards of trophic classification to the parameters such as secchi depth, total inorganic nitrogen, phosphate phosphorus and chlorophyll-a, the trophic level of seawater in Mokpo harbour was evaluated to be in eutrophic state in summer. The estimation of pollution index by eutrophication showed the seawater quality of Mokpo harbour to deteriorate and fall under the regular grades. The results of eutrophic index estimation showed the high otentiality of red tide occurrence in Mokpo harbour.
A study on the spreading of an oil slick under the influence of gravitational and viscous forces
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 63~67
In this study, some approximate theoretical solutions about oil spreading under the influence of gravitational and viscous forces have been derived from the viewpoint of energy conservation. The theoretical model which derived newly is in agreement with Toi's one derived from a different hypothesis, and shown to predict well the spreading distance of oil front at an initial step of outflow, but further study is necessary to evaluate the spreading distance after longer time
An Electrolytic Treatment of Shipboard Sewage by Using DSA Electrode (I) -Batch Electrolytic Treatment-
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 69~76
Each factor for the most effective electrolytic reaction in treating shipboard sewage was enhanced by means of batch electrolyitc reactor using DSA electrode. The effective clearance was 6mm and pH was 5-6. In such case, more than 20% of sea water concentration was needed to attain 90% of COD removal rate. The suspended solids was effectively removed by electro-floatation in proportion as charged current density. The nitrogen and posporous were effectively removed in the electrolytic device when mixed seawater.
An Electrolytic Treatment of Shipboard Sewage by Using DSA Electrode(II) -Continuous Electrolytic Treatment-
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 77~84
For the effective treatment of shipboard sewage continuously, a non-diaphragm electrolytic treatment device using DSA type insoluble electrode, Ti/IrO2, anode and H-C metal cathode, was studied. The most effective electrolytic conditions were obtained when cell clearance, 6mm, pH 5-6 and the concentration of seawater, more than 20% as batch test results. The COD removal rate was varied in logarithmic function, showed as C=Coe-KE and the required current was E = A/QCo [A.min/mgCOD]. When the COD removal effeciency was more than 90%, the electrolytic reaction constant was 0.02.
A stability analysis of oil film on an adhesion-type oil skimmer
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 85~92
To determine an operational condition of an adhesion-type oil skimmer, it is important to estimate the withdrawal rate for a given driving velocity of the skimmer and material properties of the oil. As a theoretical model for this problem the formation of an oil film on a vertically driven flat plate is investigated. The previous steady-state analysis made in the field of coating industry are reviewed. These studies have been made under the assumptions of small Reynolds and capillary number, which is adequate for coating process but not for oil skimming. An alternative analysis based on the linear stability theory is made. Comparisons with the experimental results reveal that the stability analysis gives a correct estimation of the withdrawal rate for high capillary number at which the previous theory losses its validity.
Optimal Designs for the Experiments related with Marine Environment
Journal of the Korean Society of Marine Environment & Safety, volume 3, issue 2, 1997, Pages 93~103
This paper develops a new heuristic, the Excursion Algorithm(EA), for constructing optimal designs for the experiments related with marine environment. The proposed EA consists of three parts: 1) construction of an initial feasible solution, 2) excursions over a bounded region, and 3) stopping rules. It is the second part that distinguishes the EA from the other existing heuristic methods. It turns out that excursions over a bounded feasible and/or infeasible region is effective in alleviating the risks of being trapped at a local optimum. Since this problem is formulated for the first time thesis, other heuristic algorithms do not exist. Therefore, global optimal solutions are obtained by complete enumeration for some cases, and the performance of the EA is evaluated in terms of solution quality. Computational results show that the proposed EA is effective in finding good(or, in many cases, global) solutions to the constrained optimal experimental design problems.