• Composites Research
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• v.18 no.4
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• pp.1-7
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• 2005

In-situ structural health monitoring of filament wound pressure tanks were conducted during water-pressurizing test using embedded fiber Bragg grating (FBG) sensors. We need to monitor inner strains during working in order to verify the health condition of pressure tanks more accurately because finite element analyses on filament wound pressure tanks usually show large differences between inner and outer strains. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. We fabricated a standard testing and evaluation bottle (STEB) with embedded FBG sensors and performed a water-pressurizing test. In order to increase the survivability of embedded FBG sensors, we suggested a revised fabrication process for embedding FBG sensors into a filament wound pressure tank, which includes a new protecting technique of sensor heads, the grating parts. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding.

• Ocean Systems Engineering
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• v.12 no.2
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.96-104
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• 2000

By using the offshore type submersible platform, Artificial sea floor anchored at a depth of forty meters several experimental studies have been conducted successfully during 1996. The facility consists of an artificial sea floor that floats at 7 meters below the surface, a machinery hut that projects above the surface at the center of the structure and a balance weight beneath the structure. The facility can be surfaced easily by using a water discharging pump in the water tank which is located at the center of it. To find out the behavioral character and the gathering factor of fishes around the artificial sea floor, investigations were carried out during the daytime and nighttime by direct observation and by echo-sounder. Around the testing reefs and artificial sea floor, six kinds of fishes were found by diving observation and the dominants were Scomber japonicus, Sebastes thompsoni and Oplegnathus fascitus. As Scomber japonicus was distributed around the artificial sea floor in dense small school, they were not seen elsewhere in the survey area. The artificial sea floor was concluded to act as a schooling ground far Scomber japonicus, Sebastes thompsoni and Oplegnathus fascitus. were close to the testing reefs(within 10m) in the daytime, and were thought to settle on the testing reefs at nighttime, To examine the distribution of 7shes around the artificial sea floor, an acoustic survey over a 1$\times$1km area, 0-50m in depth during the all day. Around the artificial sea floor many thin scattering fish echo(TS-54.5~ -51.5dB) and dense fish echo(TS-41~-38dB) were mainly distributed. Many scattering fish echoes, which were thought to be a mixture of small squid, pelegic crustacea and ethers, were distributed over the whole survey area. A dense fish school stayed beneath the artificial sea floor for a short duration. These phenomena were concluded to show an attraction and detention function of the artificial sea floor.

• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.16-28
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• 2008

Recent growth in LNG market has led dramatic increase in new buildings of LNG carriers and several large LNG carriers are now being constructed by shipbuilders in Korea. Large size LNG carriers has brought keen concerns on the issue regarding safety of cargo containment systems and sloshing impact load which is the critical source of loads on the membrane type containment systems. Up to the present, the best way to properly assess sloshing impact pressures on surrounding walls is a model testing for wide-ranged excitation conditions. These impact pressures obtained from model tests sometimes need to be interpreted to full-scale values and in the near future this necessity will be strengthened for more rigorous and direct safety assessment of LNG cargo containment system. In this paper, a basic experimental study is carried out with two different sized, 2D identically shaped model tanks excited in simple translational motions. Relationships between pressures of different sized model tanks are investigated Model tanks are filled with fresh water and equipped with same sized pressure sensors.

• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.141-148
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• 1996

The pulished works on Accelerated Curing Effect were generally performed around from 1960 to 1970th century for 18 to 24 hours - total curing periods. It is not possible to define the effect of temperature rise because those results were obtaine mainly by using the manually operated steam-curing tank. Thus, it may not be available to apply those data immediately on the domestic PC wall production line. The testing specimens were made from the standard mix proportion according to those of domestic PC factories to establish a basic data for the Accelerated Curing Effect. The experimental tests were conducted according to the conditions of each sub-curing periods. By comparing the results of compression tests on de-molded and 28-day water-curing specimens, we find that the most effective curing condition to obtain more than the required design strength after 28 day of water curing may be as follows: the presteaming period does not affect seriously and less than$30^{circ}C/hr$- the rate of temperature rise andless than $82^{circ}C$ - maximum temperature are necessary. It seems that post-curing procedure is very important factor to increase the effect of accelerated curing.

• Solar Energy
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• v.7 no.2
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• pp.22-29
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• 1987

This paper dealed with thickness variation of bottom heat sotrage zone due to salinity and flow rate of extration hot brine in small test solar pond (0.5m wide, 0.5m high, 1.0m long). Testing apparatus and situation were follows: 7.1 cm of height of suction diffuser and 1.8cm of height of discharge diffuser above the test pond respectively, 0.3cm of slot size of suction diffuser, 1.0cm of slot size of discharge diffuser, 47cm of length of the slot; heating of hot water ($75^{\circ}C$) through separated hot water tank, discharge of the brine into storage zone through discharge diffuser, the extration of the brine through suction diffuser, circulation of the extracted brine through a heat exchanger (cooler). Following results were obtained through the experiments. 1. In small test solar pond, the typical three zone which showed up in real solar pond were established. 2. Richardson Number was used more effectively to confirm hydrodynamic stability of the stratified flow. 3. The thickness of non convective layer had a great effect on the heat storage of the bottom convective layer, then the temperature of bottom convective layer had a relation to that of upper convective layer. 4. Optimum operating condition in the test pond was on 10%-15% of salt concentration and $0.05m^3/hr$ of flow rate of extraction hot brine. 5. Following thickness of 3 zones were available to obtain under optimum operation condition: o bottom storage zone: $30%{\pm}10%$ of total pond depth o non-convective zone: $40%{\pm}10%$ of total pond depth o Upper surface zone: $20%{\pm}10%$ of total pond depth.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.173-182
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• 1997

This study is a basic research in purse seine fishery : on the behaviour of fish schools of tilapia Tilapia mossambica in the process of catch of the purse seine fishing method. The experiment was carried out for the mackerel purse seine which using of power block by fishing fleet system in the near sea of Cheju Island and as a forecast in the near future on the purse seine fishing, using of triplex net winch by one boat system in the near sea of Norway. These model purse seines were made of the scale of 1/180 of its full scale. The model purse seine test on the escaping behaviour of fish school by gap, area reducing of gap and tension of purse line was carried out in the stagnant water of experimental water tank. Designing and testing for the model purse seines were based on the Tauti's law. The results obtained were as follows : 1. When the time for the completing of pursing was 20 minutes, average swimming speed of fish school through a gap was 9.71cm/sec for powerblock seine and 9.97cm/sec for triplex seine. 2. In the case of pursing time in actual value was 20minutes, at 50 percent of the pursing, swimming behaviour of fish school in purse seine was 10% to I section, 80% to II section, 10% to III sectional direction for powerblock seine and a similar tendency for triplex seine. 3. In the case of pursing time in actual value was 20 minutes, at the time of 10 minutes have proceeded since then, area reducing rate of gap of the seine in projected front view was 63.5% for powerblock seine and 67.5% for triplex seine. 4. In the case of pursing time in actual value was 20 minutes, escaping rate of fish school by gap in projected front view was 70% for powerblock seine and 30% for triplex seine. Maximum tension of purse line was about 8.1 tons for powerblock seine and about 8.3 tons for triplex seine.