• Journal of KSNVE
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• v.7 no.2
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• pp.261-272
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• 1997

Recently washing machines are to be in lower vibration and lower sound because of better environment. Vibration problems in washing machines occur in both washing mode and spinning mode, but vibration in spinning mode becomes main problem because of its high rotating speed and continuity. Vibration while spinning is mainly due to rigid body motion of total washing system which includes suspending rods, washing bath, spinning bath, and gear sets. In this study, some researches were done in order to analyze the rigid body motion of washing system and flexible vibration of spinning bath. A basic mathematical model was established, and the effect of position of salt water and shape change of salt water case were considered. And the effect of lengths of suspending rods, attaching angles, vertical and horizontal position, stiffness of spring on the change of vibration were also considered. To identify the effect of salt water on vibration, some measurements were done. When salt water was positioned at upper part, the effect was most and this coincides with the tendency of simulation.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.776-783
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• 2020

As the refueling of a sodium-cooled fast reactor is conducted by rotating part of the reactor head without opening it, the monitoring of existing obstacles that can disturb the rotation of the reactor head is one of the most important issues. This paper deals with the ultrasonic ranging technique that directly monitors the existence of possible obstacles located in a lateral gap between the upper internal structure and the reactor core in a prototype generation IV sodium-cooled fast reactor (PGSFR). A 10 m long plate-type ultrasonic waveguide sensor, whose feasibility has been successfully demonstrated through preliminary tests, was employed for the ultrasonic ranging technique. The design of the sensor's wave radiating section was modified to improve the radiation performance, and the radiated field was investigated through beam profile measurements. A test facility simulating the lower part of the upper internal structure and the upper part of the reactor core with the same shapes and sizes as those in the PGSFR was newly constructed. Several under-water performance tests were then carried out at room temperature to investigate the applicability of the developed ranging technique using the plate-type ultrasonic waveguide sensor with the actual geometry of the PGSFR's internal structures.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.3
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• pp.373-382
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• 2013

In this study, a biological odor treatment system was proposed to remove odor(foul smell) materials causing several problems in the closed sewage treatment plant. This odor treatment system was composed of a two-step biofilter system in one reactor. The two-step biofilter reactor was constructed with natural purification layer in upper part and artificial purification layer in lower part. The reed grasses of water purification plants were planted in the surface area and mixed porous ceramic media were filled with the lower part of biofilter reactor. By using the above experimental apparatus, the ammonia gas removal efficiency was attained to 98.3 % and the hydrogen sulfide gas removal efficiency was appeared more than 97.7 % which shows more effective than the conventional odor removal process.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1570-1576
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• 2008

Construction of the water-friendly facilities in the apartment complex and industrial complex became popular these days. In planning water-friendly facilities, kinds, layouts, water sources, water quality and water circulation system should be studies. In this study, several alternatives for a regional industrial complex project were studies and a most reasonal alternative was selected. A main canal across the central part of the complex is the principle facility with ponds and parks. The water source alternatives were a river nearby, a reservoir, ground water and urban water supply system. For each system, water quantity and quality, circulation system, permit and maintenance were compared. The facilities should be constructed with natural material such as rock and gravel. Average depth and velocity in the canal should be 10 cm and 0.15 m/s, respectively in order to people can feel the water flow in the canal. Based on the comparison, it is found that using the ground water, and water circulation system with storage tanks at the upper and lower ends of the canal system is the best alternative.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.312-320
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• 2015

The 1/5 scale-down model of the Bycatch Reduction Device (BRD) from an Argentinean demersal trawl was tested in a circulating water channel. The BRD is designed to help small Hake (merluza, merluccius hubbsi) to escape from a trawl. It is settled in front of a trawl codend, and is equipped with selection grids that help small fish to escape from the gear and guiding panels that help fish to meet with the grids. Bars of the grids are wires covered by the PVC and other parts of the BRD are made of net. When the velocity was less than 0.65 m/sec (2.81 Kont when translated to real towing speed) which is slow speed compared with real towing speed, position between an upper guiding panel and an upper selection grid were good to help small fish to escape. When the velocity was more than 0.8 m/sec (3.41 Knot when translated to real towing speed) which is similar to and faster than real towing speed, it was considered that small fish may have difficulties in escaping because the gap was not enough between an upper guiding panel and an upper selection grid. The lower selection grid was sat on the bottom of the tank without an angle due to the weight that it carries. Improvements were proposed to position the panels and the grids better.

• Journal of Wetlands Research
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• v.1 no.1
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• pp.1-5
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• 1999

We could know that the Woopo and Mokpo wetlands, which have the typical colony structure in the agricultural area of korea, had a characteristic which the pollution sources of water are scattered widely and it is caused by sewage, livestock wastewater and non point sources. As the result of an examination of water, the concentration of T-N was measured highly within five grade in the lake standard. If we build natural domestic treatment system in Taehap-myon, lbang-myon and Yuo-myon, which are located at the upper stream of wetlands, we can remove SS, BOD, COD and T-N largely.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.6-10
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• 1999

The field size can be beam output, therefore MonitorUnit can be varied due to field size dependence The purpose of this study is to evaluate and compare the dose variation according to exchange of collimator The measurements were perfomed with Wellhofer dosimetry system(water phantom. ion chamber. electrometer. system controller. build up cap. etc)and two types of linear accerlerator (Mevatron KD, MevatronMX) Scatter can be affected to field size dependence and scatter correction is separated into collimator and phantom components, scatter components can affect by exchanging of collimator Measurements of collimator scatter factor(Sc) was done in air with build up cap. 1)Square field (5cm2 to 40cm2) was measured 2)and then keeping the upper jaw constant at loom and varing lower jaw from 5cm to 40cm, 3)keeping the lower jaw constant at 10cm and varing upper jaw from 5cm to 40cm Measurements of total scatter factor(Scp) was done in water at Dmax as the procedure of collimator scatter factor measurements in water Dmax The total scatter factors were obtained to the following equation(Sp=Scp/Sc) The measured data is normalized to the data of reference field size($10{\times}10$), rectangular field is inverted to equivalent field to compare three field size data As the collimator setting is varied, the output was changed In conclusion, the error was obtained small but it must be eliminated if we intend to reach the common stated goal of $5\%$ overall uncertainty in dose determination

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.40-48
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• 2008

The Waimea Basin is located on the northern tip of the South Island of New Zealand. It is a highly productive area with intense water use with multi-stakeholder interest in water. Irrigation from the underground aquifers here makes up the largest portion of used water; however the same aquifers are also the key urban and industrial sources of water. The Waimea/Wairoa Rivers are the main sources of recharge to the underlying aquifers and also feed the costal springs that highly valued by the community and iwi. Due to the location of the main rivers and springs close to the urban centre the water resource system here has high community and aesthetic values. Recent enhanced hydrological modelling work has shown the water resources in this area to be over allocated by 22% for a 1:10 year drought security for maintaining a minimalistic flow of 250 l/s in the lower Waimea River. The current irrigated land area is about 3700 hectares with an additional potential for irrigation of 1500 hectares. Further pressures are also coming on-line with significant population growth in the region. Recent droughts have resulted in significant water use cutbacks and the threat of seawater intrusion in the coastal margins. The Waimea Water Augmentation Committee (WWAC) initiated a three year stage 1 feasibility study in 2004/2005 into the viability of water storage in the upper parts of the catchment for enhancing water availability and its security of supply for consumptive, environmental, community and aesthetic benefits downstream. The project also sought to future proof water supply needs for the Waimea Plains and the surrounding areas for a 50 - 100 year planning horizon. The broad range stage 1 investigation programme has identified the Upper Lee Catchment as being suitable for a storage structure to provide the needs identified and also a possibility for some small scale hydro electricity generation as well. The stage 2 detailed feasibility investigations that are underway now (2007/2008), and to be completed in two years is to provide all details for progressing with the next stage of obtaining necessary permits for construction and commissioning a suitable dam.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.565.1-565
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• 2001

This study aimed to compare the efficiency of propylene glycol (PG) and distilled water (DW) as vehicles that would allow diffusion of dye through the root canal system. Human maxillary central incisors were chosen and de-crowned. After enlarging the upper part of the root canal with a Peeso reamer, cementum covering the upper third of the root was removed. The roots were ultrasonically irrigated with 5% NaOCI to remove smear layer.(omitted)

• Journal of Environmental Science International
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• v.17 no.8
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• pp.833-840
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• 2008

Deoxygenation process in which CBOD(carbonaceous BOD) is biochemically oxidized to reduced inorganic compounds is of great significance in the oxygen demand of stream waters. The CBOD decay rate has traditionally been determined in a laboratory by CBOD bottle incubation method. But in this study, CBOD decay rates were obtained by laboratory incubation method and natural waters experiment. Average CBOD decay rate for the Nakdong river(upper zone) in natural waters were 0.553 $day^{-1}$ during April 2005 to January 2007. The values in the middle and down parts of the Nakdong river in natural waters were 0.384 $day^{-1}$ and 0.252 $day^{-1}$ at the same period of time, respectively. Average CBOD decay rates using by incubation method in the upper/middle/down parts of the main stream in the Nakdong river basin was 0.270 $day^{-1}$, and 0.289 $day^{-1}$, and 0.283 $day^{-1}$ during April 2005 to January 2007, respectively.