• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.423-428
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• 2014

Ice loads may be conveniently categorized as local ice loads and global ice loads. Local ice loads are often defined as ice pressures acting on local areas of shell plates and stiffeners. Therefore, local ice loads are defined in all ice class rules. However, directly measuring the local ice pressure using the actual ice class vessel is a very difficult task because appropriate instruments for direct measurement must be installed on the outer hull, and they are easily damaged by direct ice contacts/impacts. This paper focuses on the estimation of the local ice pressure using the data obtained from icebreaking tests in the Arctic sea in 2010 using the Korean icebreaking research vessel (IBRV) ARAON. When she contacted the sea ice, the local deformation of the side shell was measured by the strain gauges attached to the inside of the shell. Simultaneously, the contact area between the side shell and sea ice is investigated by analyzing the distribution of the measured strain data. Finally, the ice pressures for different contact areas are estimated by performing a structural analysis.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.41-46
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• 2008

It is a recent trend for advanced ships and submarines to incorporate composite structures with viscoelastically damping material. Much research has been done on curve-fitting techniquesto identify vibration characteristic parameters such as natural frequencies, modal damping ratios, and mode shapes of the composite structure. In this study, an advanced technique for accurately determining vibration characteristic of a circular cylindrical shell-attached viscoelastically damping material is used, based on a multi-degree of freedom (MDOF) curve-fitting method. First, an initial value is obtained by using a linear least square method. Next, using the initial value, the exact modal parameters of the composite circular cylindrical shell are obtained by using a nonlinear least square method. Results show computation time is greatly decreased and accurate results are obtained by the MDOF curve-fitting method.

• Journal of the Ergonomics Society of Korea
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• v.30 no.2
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• pp.339-347
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• 2011

Objective: The purpose of this study was to evaluate of various material of pillows by using biomechanical variables such as the cervical stability, head pressure distribution, and muscle activity. Method: Eight subjects participated in the experiment. Three different materials such as polyester sponge, memory foam and the buckwheat shell used for Korean traditional pillow were tested. Electro-goniometer, six channels of electromyography(EMG), ten channels of the head pressure sensors were used to measure the biomechanical responses. Surface electrodes were attached to the right/left semispinals capitis(RSC, LSC), the right/left sternocleidomastoid(RSM, LSM), the right/left upper trapezius(RUT, LUT). The cervical stability was evaluated by the angle deviated from the standing neck position. The head pressure distribution was evaluated by the pressure per unit area recorded on the sensors and the intensity of peak pressure. Electromyography(EMG) data were analyzed by using root mean square(RMS) and mean power frequency(MPF). Results: The buckwheat shell material showed a higher stability in the cervical spine then the other pillows during spine position. In terms of head pressure distribution, the memory form indicated the lowest pressure at supine position, buckwheat shell material indicated the lowest pressure during lying down to side, and polyester cushion recorded the highest pressure at all postures. Conclusion: The buckwheat shell material has a biomechanical advantage to maintain a healthy neck angle and reduce the pressure on the head, which means the buckwheat shell is a potential material for ergonomic pillow design. The pillow with memory form showed second best biomechanical performance in this study. Application: The shape of the buckwheat shell pillow and the characteristics of materials can be used to design the pillow preventing neck pain and cervical disk problems.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.1
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• pp.129-136
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• 2007

The component parts of the shell plate of a ship are steel. but the screw propeller or the bow thruster is a compound of bronze, nickel and aluminum. On account of the these different components between metals of the shell plate, the screw propeller and the bow thruster, which are underwater, the shell plate of a ship is corroded by the action of ionization. Authors investigated the corrosion loss of the zinc anodes which were attached to the bottom shell of the training ship Kaya for about two years. The obtained results were as follows:1. In case of the shell plate the difference of the corrosion loss according to port and starboard was almost nothing. But the corrosion loss of the forward part was more than that of the aftward part.2. There was little difference in the corrosion loss between the forward and the aftward part on the bilge keel.3. The corrosion loss of the fore, midship and aft part on the false keel were 24.7%, 22.4% and 23.9% respectively.4. The corrosion loss of the fore and the aft part on the false keel was more than that of the midship part.5. The corrosion loss of the bow thruster was greater than any other parts.6. The nearer the zinc anode to the screw propeller the more the corrosion loss on the stern frame, and the situation was also same as on the rudder.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.25-34
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• 2003

In the present paper, formulation of a nine-node assumed strain shell element is modified and extended for analysis of actuator embedded/attached structures. The shell element can alleviate locking and has sic DOFs per node by discarding assumption of no thickness change. In modeling of the physicalquantities, we have assumed linear strain field through the whole thickness direction. The electric and mechanical quantities have been coupled through the constitutive equations. Unlike typical shell element, the present shell element allows thickness change. Thus, three-dimensional piezoelasticity can be accurately simulated. Base on the formulation, a finite element program is generated and the code is validated by solving numerical examples. The results from the present work are well agreed with those from other references.

• Journal of KSNVE
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• v.6 no.6
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• pp.801-818
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• 1996

Free vibration analyses of circular cylindrical shells attached with plate structures for the symmetric boundary condition such as simply-simply supported shells by receptance method are found in literatures. However analyses of those shells with unsymmetric boundary condition as clamped free boundary are hardly found. Here frequency equation of the clamped free circular cylindrical shell with end plate is derived using receptance method and natural frequencies of the combined system were calculated. The frequencies and mode shapes obtained from present method are compared with those of ANSYS to show the validity of the method. Natural frequencies and mode component ratios of clamped-free cylindrical shell are obtained by employing Rayleigh-Ritz method on energy equations, and they are used in receptance calculation. Results show good agreement with those of ANSYS analyses.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.217-222
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• 2009

High-speed EMU under development vibrates more than a articulated high-speed train since power units are attached on each vehicle and railway vehicle. In this study, anisotropic equivalent stiffness of a aluminum extrusion plate were calculated to know and predict vibration characteristic of High-speed EMU under development. Eigen frequencies and modal shape of high speed train vehicle were calculated. And vibration generated was predicted at each position of vehicle when vehicle was operating.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.3
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• pp.223-230
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• 2010

To compare seed collection and the growth of Anadara subcrenata in Suncheon and Boseong Bays, environmental factors and the growth of larvae and spats were investigated from August 2008 to July 2009 in commercial farming sites in both bays. The variation in water temperature in both bays was similar, but the salinity was lower in Suncheon Bay than in Boseong Bay. The chlorophyll-a content was higher in Suncheon Bay due to the large inflow of freshwater. The density and shell length of A. subcrenata larvae did not differ significantly between the two bays. However, the relative growth of shell height to shell length was significantly higher in Suncheon Bay (P<0.05). The growth of A. subcrenata spats attached to a collector was significantly faster in Suncheon Bay (P<0.05). The spats in Suncheon and Boseong Bays grew to 24.3 and 21.0 mm in shell length, respectively, within 1 year after spawning, and the shell length reached 35.6 and 34.8 mm, respectively, within 2 years of spawning. The initial spats density was higher in Boseong Bay, but the growth of spats was better in Suncheon Bay. The faster growth of A. subcrenata in Suncheon Bay can be explained by the high chlorophyll-a content in this bay. Based on the low survival (%) and slower growth rate of spats in Boseong Bay, the commercial culture density of A. subcrenata in Boseong Bay should be reduced to the optimum level of the carrying capacity.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.1
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• pp.1-12
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• 1970

The propeller induced pressure fluctuation around a ship's stern is one of the interesting problems from viewpoints of the noise and vibration. Most of the experimental works on the subject employ pressure transducer attached on hull surface near the propeller. In the technique, the measured pressure includes the hydrodynamic pressure transducer attached, if they exit. Hence, the separation of the additional pressure due to vibration from the measured pressure is essential for the determination of true values of the propeller induced pressure. In this paper, to contribute to the separation method, the author investigated the additional hydrodynamic pressure as below, based on the numerical calculation. (1) Hydrodynamic pressure on the body surface of two dimensional cylinders of some mathematical sections such as ellipse, rectangle, Lewis form of hypotrocoidal charactor and curvilinear-element section with chines oscillating vertically at high frequency in a free surface. (2) Hydrodynamic pressure on the surface of the shell plate in local vibration in an ideal fluid.

• The Korean Journal of Zoology
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• v.11 no.1
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• pp.1-4
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• 1968

1. Infectious glochidia are attached only on the young fish of Zacco platypus which ranged from 2 to 4 cm in total body length. 2. The attachment of the glochidia on the fish was found at the beginning of April. 3. The glochidia per infectious fish are shown to be 1.6 in average number. 4. the glochidia were dropped from the infectious fish completely from late April through early May. 5. Most glochidia released from mother shell are attached on the fins on infectious fish, and also on the eyes, nose, mouth and gill. 6. The largest number of the glochidia was attached on the caudal fins of infectious fish, and the next was pectoral fins.