• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.2
• /
• pp.140-149
• /
• 2008

This study evaluated the efficiency of an oil fence and spreading devices for one vessel in a towing tank. A series of model experiments and numerical calculations were conducted using an existing oil fence for two vessels and a new method for one vessel. Models of the oil fence and spreading devices were constructed on $1/20^{th}$ scale from waterproofed nylon fabric and canvas. The tensions acting on the model of the oil fences and the horizontal distance between the spreading devices were calculated numerically while the oil fences were being towed. The results were extremely close to the results of the model experiments. The ratio of the opening width to the total length of the oil fence, which shows the efficiency of the oil fence for one vessel, was 49.7% in 0.4 m/sec. Therefore, the proposed oil fence system should be very useful for oil containment at sea. As the opening width of the oil fence is not proportional to the length of the towing rope, it may be reasonable to maintain the towing rope at approximately 100 m. Furthermore, a reasonable towing speed, when operating the oil fence for one vessel equipped with spreading devices, was within 0.4 m/sec.

• Archives of Craniofacial Surgery
• /
• v.19 no.3
• /
• pp.235-239
• /
• 2018

Intraoperative expansion has been used to cover small to large defects without disadvantages of the conventional tissue expanders. Various materials, for example, expanders and Foley catheters are being used. We introduce a new, convenient and economical device immediately available in the operating room, according to the defect size for intraoperative expansion, with latex gloves or balloons. The retrospective study was done with 20 patients who presented with skin and soft tissue defects. During the operation, expansion was done with latex gloves or balloons inflated with saline through an intravenous line and a three-way stopcock. After the inflation, the glove was removed and skin was covered with expanded tissue. A careful decision was made regarding the inflation volume and placement of the expander according to the defect size. There were no postoperative complications. The skin contracture and tension was minimal with a texture similar to the adjacent tissue. The new intraoperative expansion devices with latex gloves and balloons were cheap and made easily right in the operation room. The reconstruction of small to large sized skin defects can be done successfully, functionally and aesthetically without using expensive commercial materials.

• Nuclear Engineering and Technology
• /
• v.51 no.1
• /
• pp.228-237
• /
• 2019

The crack growth responses of as-received and as-welded Alloy 600/182 and Alloy 690/152 welds to constant loading were measured by a direct current potential drop method using compact tension specimens in primary water at $325^{\circ}C$ simulating the normal operating conditions of a nuclear power plant. The as-received Alloy 600 showed crack growth rates (CGRs) between $9.6{\times}10^{-9}mm/s$ and $3.8{\times}10^{-8}mm/s$, and the as-welded Alloy 182 had CGRs between $7.9{\times}10^{-8}mm/s$ and $7.5{\times}10^{-7}mm/s$ within the range of the applied loadings. These results indicate that Alloys 600 and 182 are susceptible to cracking. The average CGR of the as-welded Alloy 152 was found to be $2.8{\times}10^{-9}mm/s$. Therefore, Alloy 152 was proven to be highly resistant to cracking. The as-received Alloy 690 showed no crack growth even with an inhomogeneous banded microstructure. The cracking mode of Alloys 600 and 182 was an intergranular cracking; however, Alloy 152 was revealed to have a mixed (intergranular + transgranular) cracking mode. It appears that the Cr concentration and the microstructural features significantly affect the cracking resistance and the cracking behavior of Ni-base alloys in PWR primary water.

• Tribology and Lubricants
• /
• v.38 no.5
• /
• pp.185-190
• /
• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.3
• /
• pp.286-291
• /
• 2024

Research on aged insulation of cables by stress is constantly being considered for reliable and stable power transmission of offshore wind farms. This study aimed to evaluate the insulation characteristic of aged XLPE (cross-linked polyethylene) insulation for application of offshore wind farms. In this study, The XLPE insulation of cable was set as various mechanical strains. The XLPE insulation is exposed to the mechanical stress below yield strain of 5%, 10%, and 20%. Aged samples were tested by using the method of AC BDV (alternative current breakdown voltage), tensile strength, elongation, and SEM (scanning electron microscope) to obtain insulation characteristics. The experimental results show that the dielectric breakdown of the sample with a strain 20% was 50% lower than the unaged sample; thereby, demonstrating that the mechanical strain that occurred in the submarine cables can weaken the insulation characteristics. Therefore, mechanical strain should be monitored when laying and operating submarine cables for offshore wind farms.

• Korean Journal of Environment and Ecology
• /
• v.32 no.2
• /
• pp.203-214
• /
• 2018

This study was conducted to investigate the types, socio-demographic characteristics, use patterns, and visit motivations of visitors to "Jangseong Pyunbaek Healing Forest (JPHF)." Data were collected from 216 samples selected by convenient sampling method using questionnaire survey between October and November 2016. Data obtained from 476 respondents of the same type of survey during the same period were partly used to examine the types of activities of visitors to the study site. The results showed that 77.0 percent of respondents were categorized as "visitor for recreation" (VR: Those who visit JPHF for the purpose of general recreational experiences such as appreciating landscapes, tourism, social interactions rather than better health or healing). On the other hand, only 10.3 percent of respondents were "visitor for healing" (VH: Those who visit JPHF for the purpose of better health or physical and mental healing). VH showed a higher level of visit experiences to JPHF than VR and tended to expect JPHF as "the place to enjoy calm and natural experiences" more than VR did. VH tended to visit JPHF "alone" more, and their group size was also smaller than VR. About 26.8 percent of all respondents were not aware that JPHF was the "healing forest," and VH showed higher awareness of it than VR. About 66.8% of respondents assessed the managerial and operating states of JPHF positively while only 6.2% assessed them negatively. There was no difference in the assessment of managerial and operating states between VR and VH. The visitors of JPHF showed the markedly high use in main forest roads (use rate: 47.4%) and "Healing Field" (use rate: 59.2%) of JPHF. Regarding the visit motivations to JPHF, VH showed higher importance on "quietude," "health," and "tension release" than VR while VR rated higher importance on "social interaction." The paper discussed the managerial implications, findings, limitations and further studies.

• Korean Chemical Engineering Research
• /
• v.52 no.5
• /
• pp.632-637
• /
• 2014

A microfluidic method for the in situ production of monodispersed alginate hydrogels using biocompatible polymer gelation by crosslinker mass transfer is described. Gelation of the hydrogel was achieved in situ by the dispersed calcium ion in the microfluidic device. The capillary number (Ca) and the flow rate of the disperse phase which are important operating parameters mainly influenced the formation of three distinctive flow regions, such as dripping, jetting, and unstable dripping. Under the formation of dripping region, monodispersed alginate hydrogels having a narrow size distribution (C.V=2.71%) were produced in the microfluidic device and the size of the hydrogels, ranging from 30 to $60{\mu}m$, could be easily controlled by varying the flow rate, viscosity, and interfacial tension. This simple microfluidic method for the production of monodisperse alginate hydrogels shows strong potential for use in delivery systems of foods, cosmetics, inks, and drugs, and spherical alginate hydrogels which have biocompatibility will be applied to cell transplantation.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.36 no.3
• /
• pp.166-174
• /
• 2000

Anchovy, EngrauEis japonica scoop nets are used in the coastal of Southern and Cheju of Korea. Especially in the Cheju, the fishing gear of scoop nets consists of upper boom, lower boom, pressing stick and bag net. They are operated by fishing boats of 6 to 10 ton class and 8 persons on board. The booms are controlled by side drum, and the net and pressing stick are hauled by only human power in operating. Therefore this fishery needs to large labor and heavy human power and has much risk. Three kinds of hydraulic winding device which controls two booms was designed and manufactured to reduce heavy labor force of scoop nets, and trial in the sea was carried out to test their performances using the commercial fishing boats of 6 ton class. The proper capacity of hydraulic pump and motor were determined by model test of boom 1/5 scale. The results obtained are as follows, 1. Tension of boom which is being drawn was the strongest and 187.5kgf when the boom's end is in the depth of 4m under the water. 2. The hydraulic motor of the fittest kind of winder has the least leakage per time than the other kinds. 3. In the best type of several winder devices, when the pressure difference was fixed $130kg/^2$ for the safe fishery, the winding velocity of boom line was 2m/sec, is faster 0.48/sec than traditional fishing method and this winder can catch the anchovy of 1.6 tonnage. 4. As a result, the crew were decreased from 8 to 6 and the problem of heavy human power and risk on fishing operation were solved by using the this winder.

• Fire Science and Engineering
• /
• v.29 no.2
• /
• pp.79-83
• /
• 2015

The fire accident is a representative type of disaster that can largely impact on business. Therefore, precautionary measures and rapid initial response is very important when a disaster occurs. The storage of porous combustibles is inevitable in coal yard, plywood processing industry, and others that are currently operating. Initial fire fighting of fire and identifying the ignition point in such a porous combustible storage space are so difficult that if the initial response is failed, being led to deep-seated fire, surface fire is likely to result in secondary damage. In addition, deep-seated fire can cause personal injuries and property damage due to a large amount of toxic gases and reignition. Therefore damage reduction measures is required around the storage space to handle a porous flammable. Improving the penetration performance of the concentration of the surfactant is carried out as underlying study, which is about an deep-seated fire extinguishing efficiency augmentation when using wetting agents. The porous materials used in the experiments is radiata pine wood flour, which occupies more than 75% of the domestic wood market. Fire fighting water is selected as Butyl Di Glycol (BDG), which is being used for infiltration extinguishing agent, and the experiment was carried out by producing a standard solution. The experiment was carried out on the basis of the Deep-Seated Fire Test of NFPA 18. The amount of watering, porous material to the internal amount of penetration, and runoff measurement out of the porous material was conducted. According to experimental results, as the surface tension is reduced, the surfactant concentration macroscopic penetration rate decreases, but infiltration to a porous material is shown to have growth characteristics.

• Korean Journal of Agricultural Science
• /
• v.14 no.1
• /
• pp.81-97
• /
• 1987

Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of $0.70kg/cm^2$ to $6.33kg/cm^2$, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.