• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.3
• /
• pp.409-420
• /
• 2021

The decrease in under keel clearance (UKC) due to the increase of draft that occurs during advancing and turning of very large vessels of different types was analyzed based on computational fluid dynamics (CFD). The trim change in the Duisburg test case (DTC) container ship was much smaller than that of the KRISO very large crude oil carrier 2 (KVLCC2). The sinkage of both ships increased gradually as the water depth became shallower. The amount of sinkage change in DTC was greater than that in KVLCC2. The maximum heel angle was much larger for DTC than for KVLCC2. Both ships showed outward heel angles up to medium-deep water. However, when the water depth became shallow, an inward heel was generated by the shallow water effect. The inward heel increased rapidly in very shallow water. For DTC, the reduction ratio was very large at very shallow water. DTC appeared to be larger than KVLCC2 in terms of the decreased UKC because of shallow water in advancing and turning. In this study, a new result was derived showing that a ship turning in a steady state due to the influence of shallow water can incline inward, which is the turning direction.

• Journal of the Society of Naval Architects of Korea
• /
• v.49 no.1
• /
• pp.14-25
• /
• 2012

Recently, the application and installation of the pod propeller to the cruise ship is dramatically increased. It is because pod propulsion system allows a lot of flexibility in design of the internal arrangement of a ship. To reflect this trend, many researches have conducted to use the pod propeller for the roll stabilization of a ship. In the paper, a roll stabilization controller is designed by using fins and pod propellers as the control actuators for cruise ships. Two kinds of control algorithms are adopted for the roll control system; LQR (Linear Quadratic Regulator) algorithm and frequency-weighted LQR algorithm. Through the numerical simulation, the effect of the turning rate of the pod propeller on the roll control system is analyzed. Analysis of the simulation results indicated that the turning rate of the pod propellers is one of the important parameters which give the significant effects on the roll stabilization.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.3 no.2
• /
• pp.25-31
• /
• 2004

Machinability in metal cutting processes depends on cutting input conditions such as cutting velocity, feed rate, depth of cut, types of work material and tool shape factors. In this study, to assess chip breaking characteristics of a turning process, an equivalent oblique cutting system to this has been established. And the equivalent effective rake angle was determined using side rake angle, back rake angle and side cutting edge angle of the tool. A non-dimensional parameter, Chip breaking index(CB), was used to assess Chip breaking characteristics of chip in conjunction with the equivalent effective rake angle. In case of positive rake angles of the equivalent effective rake, the back rake angle has little effect on the chip breaking characteristics however, in case of negative ones, the side rake angle has some effect on Chip breaking characteristics.

• The KSFM Journal of Fluid Machinery
• /
• v.7 no.5 s.26
• /
• pp.36-42
• /
• 2004

The effect of tip clearance height on the three-dimensional flow and aerodynamic loss in the wake region of a high-turning turbine rotor cascade has been investigated with a miniature cone-type five-hole probe. Distributions of velocity magnitude, secondary velocity vectors, and total-pressure loss coefficient are presented for three tip gap-to-span ratios of h/s = 0.0, 0.5 and 1.0 percent. The result shows that with the increment of h/s, tip leakage vortex tends to be intensified and aerodynamic loss due to the leakage vortex is increased as well. In the case of h/s = 1.0 percent, aerodynamic loss in the tip-leakage flow region is found dominant in comparison with that in the passage vortex region. With increasing h/s, mass-averaged secondary loss coefficient has a greater portion in the mass-averaged total-pressure loss coefficient.

• Cartoon and Animation Studies
• /
• s.41
• /
• pp.357-378
• /
• 2015

The recent domestic toy market is filled with the fever of 'Turning Mecard' produced as a character product of units showing in . The toy market of the domestic character licensing industry has shown such rapidly changing trends during the period of broadcasting contents like animation or special films targeting children. Through these contents, the characters are cognized, and also the immersion and loyalty can be increased depending on the progress of the story, on top of marketing effect while the animation is broadcasted. This effect is called gamification meaning that consumers voluntarily participate in the contents after receiving fun. Through the purchase of character products, the immersion and loyalty participate in the animation. Thus, this study analyzed the gamification elements by examining the animation and toy products of currently gaining popularity in the toy market. In the results of the study, the story structure of has the sustainment just like game, which is connected to its character product. Therefore, the users who have watched build up the relationship with each other, and the competition and reward can be done through the game using the character products, which is connected to such high immersion and loyalty.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.22 no.2
• /
• pp.22-30
• /
• 1986

It is very important for a navigator on bridge to know the maneuverability of his ship sufficiently at sea. Generally, the data of a turning circle test have long been used to study and evaluate the maneuverability of a ship. But referring only the data of the turning circle test method, he can not evaluate his ship's maneuvering characteristics sufficiently. So nowaday the test method added Z test to turning circle test for more detail references is considered to be desirable. In this paper, the authors performed PAL test and Z test together in order to study the maneuverability of M. S.Pusan 403, training ship of the National Fisheries University of Pusan. According to the results of PAL test, the rudder effect in port rudder angle of the M. S. Pusan 403 was found to be more effective than that in starboard one, because her changing amounts of angular velocity, turning radius and tangent speed in port rudder angles were found to be larger than those of them in starboard rudder one in unsymmetry. The relation between her drift angle(.8) and rudder angle (0) was found to be changing with .8=0.640 in direct proportion. As it appeared that her calculated K'-values were smaller than the standard K'-values of different kinds of ships in accordance with her Z test, her turning ability was found to be lower. The running distance of a turn in her 10$^{\circ}$ Z test was about 8.3 times her own length and was found not to be exceeded the standard maneuvering distance, therefore she was considered to have good maneuverabilities synthetically.

• Journal of Mechanical Science and Technology
• /
• v.18 no.12
• /
• pp.2182-2189
• /
• 2004

In the recent years, environmentally conscious design and manufacturing technologies have attracted considerable attention. The coolants, lubricants, solvents, metallic chips and discarded tools from manufacturing operations will harm our environment and the earth's ecosystem. In the present work, the Tukey method of multiple comparisons is used to select the minimum level of coolant required in a turning process. The amount of coolant is varied in 270 designed experiments and the parameters cutting temperature, surface roughness, and specific cutting energy are carefully evaluated. The effects of coolant mix ratio as well as the amount of coolant on the turning process are studied in the present work. The cutting temperature and surface roughness for different quantity of coolant are investigated by analysis of variance (ANOVA) - test and a multiple comparison method. ANOVA-test results signify that the average tool temperature and surface roughness depend on the amount of coolant. Based on Tukey's Honestly Significant Difference (HSD) method, one of the multiple comparison methods, the minimum level of coolant is 1.0 L/min with 2% mix ratio in the aspect of controlling tool temperature. F-test concludes that the amount of coolant used does not have any significant effect on specific cutting energy. Finally, Tukey method ascertains that 0.5 L/min with 6% mix ratio is the minimum level of coolant required in turning process without any serious degradation of the surface finish. Considering all aspects of cutting, the minimum coolant required is 1.0 L/min with 6% mix ratio. It is merely half the coolant currently used i.e. 2.0 L/min with 10% mix ratio. Minimal use of coolant not only economically desirable for reducing manufacturing cost but also it imparts fewer hazards to human health. Also, sparing use of coolant will eventually transform the turning process into a more environment-conscious manufacturing process.

• Journal of the Korean Institute of Navigation
• /
• v.10 no.2
• /
• pp.83-96
• /
• 1986

In the restricted sea way such as fair way in harbor, narrow channel etc, the safe ship-handling is a very important problem, which is greatly related with turning ability of ships. It is of great importance that ship-handlers can grasp the position of pivoting point varying with time increase at any moment for relevant steering activities. Mean while, in advanced ship-building countries they study and investigated pivoting point related with turning characteristics, hut their main interest lies in ship design, not in safe ship controlling and maneuvering. In this regards it is the purpose of this paper to provide ship-handlers better under standing of pivoting point location together with turning characteristics and then to help them in safe ship-handling by presenting fact that pivoting points vary according to configuration of ships. The author calculated the variation of pivoting point as per time increase for various type of vessels, based on the hydrodynamic derivatives obtained at test of Davidson Laboratory of Stevens Institutes of Technology , New Jersey, U.S.A. The results were classified and investigated according to the magnitude of block coefficient , length-beam ratio, length-draft ratio, rudder area ratio ete, and undermentioned results were obtained. (1) The trajectory of pivoting point due to variation of rudder angle are all the same at any time, though the magenitude of turning circle are changed variously. (2) The moving of pivoting point is affected by the magnitude of block coefficient, length-beam ratio, length-draft ratio, however the effect by rudder area ratio might be disregarded. (3) In controlling and maneuvering of vessels in harbor, ship-handlers might regard that the pivoting point would be placed on 0.2~0.3L forward from center of gravity at initial stage. (4) The pivoting point of VLCC or container feeder vessels which have block coefficient more than 0.8 and length-beam ratio less than 6.5 are located on or over bow in the steady turning. (5) When a vessel intends to avoid some floating obstruction such as buoy forward around her eourse, the ship-handler might consider that the pivoting point would be close by bow in ballast condition and cloase by center of gravity in full-loaded condition.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.13 no.5
• /
• pp.64-69
• /
• 2014

This article presents machining experiments to assess the relationship between the profile accuracy and the workpiece hardness using a natural diamond tool on an ultra-precision diamond turning machine. The study is intended to secure a corner cube prism pattern for reflective film capable of high-quality outcomes. The optical performance levels and edge images of corner cubes having various hardness levels of the copper-coated layer on a carbon steel plate are analyzed. The hardness of the workpiece has a considerable effect on the profile accuracy. The higher the hardness of the workpiece, the better the profile accuracy and the worse the edge wear of the diamond tool.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.8
• /
• pp.27-33
• /
• 2004

The ultra-precision cutting is a key technique for the manufacture of optical components such as aluminium mirrors, electroless nickel mirror, plastic mirror in a variety of advanced science and technology applications. The paper presents experimental results of ultra-precision diamond fuming of electroless nickel materials. In general, the cutting condition such as feed rate and depth of rut, have effect on the surface roughness in ultra-precision diamond turning. To obtain an optimal cutting condition, we studied the effect of the cutting speed. the tool length, the tool nose radius, the feed rate and depth of cut on the surface roughness. So, the relationship of the surface roughness and cutting condition has been clarified. From the experimental results, the machined surface roughnesses were obtained less than 1nm rms.