• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.267-273
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• 2000

The tooth selectivity of the dredge for catching venus clam (Gomphina melanaegis) was described in which the teeth penetrated the bottom and lifted the shell into the bag. Some factors affecting the selection action of the teeth of the dredge were analyzed related to shell length and shell height. The retention probability of venus clam not sifting through the gaps between the teeth was calculated for various shell lengths and was fitted to two parameter logistic selection curve. The formula obtained is as follows: $P= \frac{1}{1+exp[8.24](\frac{d}{L_1}-0.649)}$, where d is distance between teeth and $L_1$ is a shell length. For biological minimum size(25mm) of venus clam to be catchability 50% the distance between teeth was estimated 16.2mm from the logistic curve. Therefore it is desirable to extend that current spacing between teeth from 12mm to 16mm for the venus clam dredge. That space increasing enables fuel oil of vessel to drag a dredge to be reduced and also man power to sift through sifter smaller venus clams on boards to be reduced.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.32-35
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• 2011

Template has been widely used for hull forming process in most of shipyards. It is used to estimate the curvature of deformed shape in comparison with design shape. SHI (Samsung Heavy Industry) had used AutoKon system for ship manufacturing design in the past. The AutoKon used the global coordinate system of ship (frame, water line and so on) to create template data. It brought the mismatched angles between templates and a curved shell plate. The mismatched angle is measured by forming worker to place template on shell forming stage. However, the mismatched angle is difficult to place template with exactly required angle because the shell plates have various curvature and size. It causes incorrect shape of formed shell plates. The attached angle of template should be 90 degree to place template easily on forming shell plates. Currently, SHI has been applied GSCAD for ship manufacturing design process which is 3D solid modeling system. The GSCAD is the rule-based system which can automate 3D modeling and control the manufacturing data by rule. The rule can easily provide methods to create and automate template object with regular attached angle in comparison with AutoKon system. Therefore, SHI developed new template rule which it can automatically create template object with regular attached angle in GSCAD.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3014-3021
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• 2015

Shell-tube heat exchanger is widely applied in industrial field by easily manufacturing as to various size and flow patterns. In this study, by changing baffle's cut direction, tilt angle and rotational angle as well as by using SST (Shear Stress Transport) $k-{\omega}$ turbulence model in ANSYS FLUENT v.14, the heat transfer rate and pressure drop characteristics of inner shell will be analyzed to improve heat transfer ability. As a result of analysis, heat transfer performance according to cut direction of baffle has been improved with vertical model B and angle $45^{\circ}$ model C than horizontal model A. In addition, the tilt $10^{\circ}$ of the baffle and rotational angle $0^{\circ}-90^{\circ}-180^{\circ}-270^{\circ}$ of model D showed better result in heat transfer rate and pressure drop.

• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.33-40
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• 2020

Chiller systems which have better temperature stability than Direction expansion coils are often used as condensing units in HVAC systems for offshore plants. Large capacity compressors and electronic expansion valves in chiller systems are mostly imported, and the size of a chiller system depends on heat exchangers such as evaporators and condensers which are locally produced. Due to limited space in the offshore plants, shipyards are demanding manufacturers to make equipment compact. In this paper, a shell & tube heat exchanger, which is used as an evaporator in the conventional flooded chiller system, is replaced by a newly developed compact plate & shell heat exchanger. The main development process of the plate & shell heat exchanger is introduced, and its performances were experimentally evaluated with a real flooded chiller system, and the results are presented.

• Polymer(Korea)
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• v.32 no.6
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• pp.573-579
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• 2008

PBA/PS core-shell polymer nanoparticles were synthesized by two stage emulsion polymerization and hybridized with silica nanoparticle by simple mixing in emulsion state and following precipitation into water/methanol mixture dissolving $Na_2CO_3$. The stress-strain curve revealed that the elastic modulus was increased with increasing molecular weight of polymer and silica weight fraction but decreased with increasing size of core-shell nanoparticle. Especially, there was a rapid increase of elastic modulus with silica blending. As a result, 6 times higher elastic modulus was observed in PBA/PS core-shell baroplastic sample processed at 25$^\circ$C under 13.8 MPa for 5 min by blending with 13.0 wt% of silica nanoparticle.

• Polymer(Korea)
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• v.38 no.1
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• pp.80-84
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• 2014

Polymer nanoparticles with cross-linked core and PBA/PS double-shell were synthesized and their baroplastic properties were characterized. PBA/PS, the inner and outer shell with cross-linked core consisting of St and DVB were synthesized by three-stage emulsion polymerization. The obtained materials exhibited pressure-induced mixing of their components and could be processed at $25^{\circ}C$ by compression molding which means there was no effect of the presence of cross-linked core. Interestingly, the Young's modulus of molded objects has found to be affected strongly by the size of double-shell nanoparticles. Furthermore, the molded object of higher PBA content was successfully recycled 5 times at $25^{\circ}C$ and showed 0.55 MPa of modulus and 1.81 MPa of strength at break.

• Journal of Powder Materials
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• v.30 no.5
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• pp.387-393
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• 2023

Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni₃Co₆S₈-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni₃Co₆S₈@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni₃Co₆S₈@C-YS exhibited an impressive reversible capacity of 525.2 mA h g^-1 at a current density of 0.5 A g^-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni₃Co₆S₈ yolk shell nanopowder (Ni₃Co₆S₈-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni₃Co₆S₈@C-YS were attributed to the pitch-derived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.719-738
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• 2006

Simrad EM950 multibeam data and surficial sediment grab samples were acquired to correlate backscatter strength with surficial sediment properties in the eastern Yellow Sea which tidal sand ridges are dominantly developed. The study area is divided into the western sand ridge zone characterized by well sorted, fine sandy sediment, and the eastern non-sand ridge zone characterized by poorly sorted, medium sand with some gravels and shell fragments. In spite of minor difference in grain size between two zones, the variations of backscatter strength between two zones are distinct. Multibeam backscatter strength of study area shows good correlation with the grain size of surface sediment as well as the carbonate contents. High occurrence of carbonate shell fragments can increase grain size and bottom roughness. The dominance of higher backscatter strength in the eastern non-sand ridge zone may reflect the effects of coarse grain size and high shell fragments contents.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.500-507
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• 2008

• Journal of the Korean Society of Safety
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• v.34 no.3
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• pp.28-35
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• 2019

Dry water is a core-shell structured powder which comprises a very fine water core covered with hydrophobic silica particles. Recently, the dry water has attracted attention as a new type of fire extinguishing agents. However, characteristics of the dry water as a fire extinguishing agent have not been revealed until now. To our best knowledge, this is the first work to uncover effects of particle size of the dry water on the fire extinguishing performance. Pristine dry water, which has heterogeneous particle size distribution, was carefully separated by sieving method into three fractions which were a small size (ca. $110{\mu}m$) fraction, a medium size (ca. $220{\mu}m$) fraction and a large size (ca. $400{\mu}m$) fraction. Microscopic observations confirmed the effective separation of dry water's particle size. In extinguishing tests of wood cribs fire, the medium size dry water showed most excellent fire extinguishing performance, as compared to other dry waters having small (ca. $110{\mu}m$) and large (ca. $400{\mu}m$) particle size. The good performance of the medium size (ca. $220{\mu}m$) dry water may be attributed to the balance between cooling effect of the water core and smothering effect of the silica particles. It is also revealed that small size dry water has poor flowability than large size dry water.