• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.961-967
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• 2007

Automatic water feeding system for chickens is the one of the most important devices at poultry farms. Chickens drink water directly from a water feeder nipple of the automatic water feeder. Check valve inside the water feeder nipple is open when they drink water and is closed otherwise. There are two types of nipples. One is the piston nipple, and the other is the ball nipple. Because the nipple stick in the ball nipple can move freely, the sloping mechanism of the ball nipple works well. but it has complicated mechanism. On the other hand, the piston nipple has very simple structure, but its movement is limited so it can move only up-and-down. To overcome those limitation, the piston nipple with sphere valve seat face (sphere face piston nipple) has been developed and is just distributed at domestic markets. The experimental performance test of the commercialized sphere piston nipple has been conducted, and compared with the performance of the ball nipple and the piston nipple which are domestic products. As the result, sphere piston nipple shows excellent performance compared to that of the piston nipple but its performance is similar to ball type nipple.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6282-6288
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• 2014

$CO_2$ welding is used widely in the field. On the other hand, welding defects occur when welders cannot adjust the current and voltage needed for welding and have to stop working to adjust the current and voltage, causing sudden cooling down of the welding structure inside a vehicle or tank where the control panel is invisible or when work site is far. This study used three types of existing $CO_2$ welders. This also applied SS400 rolled steel for welding structural purposes for remote control torch welding, perform a welding test through v-groove butt welding with a remote control torch and existing $CO_2$ welding torch, conducted visual inspection on the appearance of a welded top bead. In addition, the appearance quality of the welding part was monitored mainly through penetrant testing and a bending test to evaluate the welding defect reduction and the effect on the performance and compatibility by replacing the existing welder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1102-1108
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• 2014

This study was to compare the protection abilities of an SPF through ground or underwater casting. A mat of 1/10 scale was made and then mortar was placed on the ground and submerged conditions. A limit velocity of each mat was estimated with this experiment. As a result of the test, the mat failed because of the decrease of bearing power in the center of the waterway. On the one hand, the edge of the mat, where the velocity is slow, secures stability. The result of the limit velocity analysis suggests that a velocity of ground placement with 6.51m/s and underwater casting with 9.80m/s is the minimum to ensure stability. When SPF mat with a thickness of 0.50m is replaced with a concrete block, it is calculated to need a maximum thickness of 2.21m.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.20-30
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• 2012

In case of analyzing PAHs (EPA 16 compounds) in oil-contaminated soils, the lump of peaks may occur because of the aliphatic and polar compounds in oil. This phenomenon is due to the lower accuracy of the analysis. To solve this problem, evaluation of application of silicagel-alumina multi-layer fraction was performed using standard substances and oil-contaminated soils. As a result of application of silicagel-alumina multi-layer fraction cleanup method using standard substances, recovery rates of surrogate standards (5 compounds including Naphthalene-d8) were 83~100% and those of target standards were 75~129%. These were to meet the target values (60~130%) in this study. When used 4% water-silicagel column analyze PAHs in oil-contaminated soils, Some problems were generated for quantitative analysis of PAHs; concentration of PAHs was underestimated due to an upward baseline of internal standard (recovery rate: less than 60%) and overestimated by the lump of peaks which were not purified (the biggest recovery rate: more than 400%). On the other hand, in case of silicagel-alumina multi-layer fraction cleanup method, recovery rate of surrogate standards were 61~101.6%. Therefore this cleanup method was considered a valid method to improve accuracy of analysis of PAHs in oil-contaminated soils.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.1-11
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• 2016

PURPOSES : This study estimated the load effect of a single heavy truck to develop a live load model for the design and assessment of bridges located on an expressway with a limited truck entry weight. METHODS : The statistical estimation methods for the live load effect acting on a bridge by a heavy vehicle are reviewed, and applications using the actual measurement data for trucks traveling on an expressway are presented. The weight estimation of a single vehicle and its effect on a bridge are fundamental elements in the construction of a live load model. Two statistical estimation methods for the application of extrapolation in a probabilistic study and an additional estimation method that adopts the extreme value theory are reviewed. RESULTS : The proposed methods are applied to the traffic data measured on an expressway. All of the estimation methods yield similar results using the data measured when the weight limit has been relatively well observed because of the rigid enforcement of the weight regulation. On the other hand, when the estimations are made using overweight traffic data, the resulting values differ with the estimation method. CONCLUSIONS : The estimation methods based on the extreme distribution theory and the modified procedure presented in this paper can yield reasonable values for the maximum weight of a single truck, which can be applied in both the design and evaluation of a bridge on an expressway.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.74-79
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• 2009

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

• Korean Journal of Microbiology
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• v.38 no.3
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• pp.180-185
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• 2002

The direct viable count (DVC) and plate count (PC) methods was used to measure the number of bacteria in potable groundwater samples collected from bottled water from the market, mineral water, and edible groundwater near the urban areas and the stock farming congested areas. As a result, the number of living bacteria by DVC was comprised 30~80% of the total direct count (TDC), whereas the number of living bacteria by PC was around l~30% of DVC. Such results show that viable but non-culturable (VBNC) bacteria exist in the potable groundwater with high percentages. On the other hand, upon measuring the value from the conventional nutrient broth (NB), $10^-2$ fold diluted nutrient broth (DNB), and R2A broth, the values from the DNB and R2A showed 2~50 times higher than the conventional NB medium. These results indicate that oligotrophic bacterial groups which can multiply in the low nutrient broth abundantly exist in the oligotrophic environment like potable groundwater.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.2
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• pp.82-89
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• 2011

Methylcyclohexane is frequently used in industrial sites (2,592tons/year) as rubber adhesives, ink, paint thinners, organic solvents, and so on. However, there are limited data on the toxic evaluation of methylcyclohexane. This study aims to predict the hazards and neurological effects of methylcyclohexane using SD rats in order to prevent health disorders of workers. The OECD Guideline for Testing of Chemicals (OECD, 2001) was used as a reference during the tests. For 13 weeks (once a day, five days per week) 0, 10, 100 and 1,000mg/kg/day of methylcyclohexane was injected to SD rats to observe any changes in the body or organ weight, hematology, histopathology, mobility, blood pressure, and neurotransmitter. As a result, some male and female SD rats injected with 1,000mg/kg/day of methylcyclohexane died. On the other hand, surviving rats showed significant changes such as hematological changes involving the decrease in the number of red blood corpuscles, and the decrease or increase in the weight of the lungs, kidneys, spleens, and livers (p< 0.05, p<0.01). Also histopathological lesions were observed in the hearts and kidneys. In the test for the effect on the nervous system, SD rats injected with 100mg/kg/day of methylcyclohexane had higher blood pressure levels compared to the control group. However, no abnormal effects was observed in the mobility, serotonin, neurotransmitter, and the biopsy of the brain and coronary arteries. The study results revealed that the livers, hearts, and kidneys were affected by methylcyclohexane. The absolute toxic dose of methylcyclohexane is 1,000mg/kg/day, NOAEL is 100 mg/kg/day, and it is not a toxic substance to the nervous system.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.135-143
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• 2005

It was evaluated that the effect of turbidity removal by Pore Controllable Fiber Filter(PCF) installed in NS(Naksang) small water treatmant plant(system) using under flow water as raw water in the study. The results of the study are as the followings. Firstly, the removal efficiency of turbidity by PCF without coagulation(in operation mode not using coagulants) was mostly below 20 percent. On the other hand, when operation using proper coagulants, that of turbidity was mostly over 80 percent. Secondly, slow sand filtration after PCF, total turbidity removal efficiency of final treated water was 84.3 percent, and the contribution by PCF was 57.1 percent and that of slow sand filtration was 27.7 percent. Therefore the introduction of PCF as pre-treatment process would be helpful to reduce the loading of high turbidity of slow sand filtration. Thirdly, the results of particle counter measurements showed that when operated PCF with coagulants, fine flocs captured or adsorbed at the pore of PCF were flow out into the effluents from 120 minutes after backwashing because of the increase of headloss of PCF. Therefore the decision of backwashing time should made consideration into the outflow of fine flocs from PCF. Fourth, coagulant dosages on PCF at the same turbidity was largely variable because of the effect of the raw water characteristics and the turbidity increase velocity at rainy days, therefore flexible coagulant dosages should be considered rather than fixed coagulant dosage by the influent jar-test result.

• Journal of Preventive Medicine and Public Health
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• v.30 no.3 s.58
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• pp.555-566
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• 1997

This study was carried out to evaluate the cytotoxicity of rock wool fibers(RWFs) such as cell division disturbance, chromosomal and DNA damage, and mutagenicity using cultured cells. RWFs were the man made mineral fibers. In order to find the correlation between the cytotoxicity of RWFs and the phagocytic capacity of cells, the phagocytic processes were observed using scanning electron microscope. Cell division disturbance by RWFs was evaluated by the formation of multinucleated giant cells. The chromosomal damage was evaluated by the micronucleus formation. For the evaluation of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine (8-OH-dG) formation was measured utilizing calf thymus DNA. Mutagenicity was determined by the point mutation of HGPRT and the effect of RWFs on cell transformation was also observed. 1. Compared with the results of chrysotile, RWFs were no or little effect on the cell growth according to the results done by the tests of cell proliferation inhibition and relative plating efficiency. 2. The frequency of multinucleated giant cell formation was increased by the treatment of RWFs and it was dose-dependent. However, the effect of RWFs was weaker than that of chrysotile. 3. The number of micronuclei formed in the RWFs treated cells was between those of cells treated with chrysotile and those of untreated cells. 4. The 2 fold increase in the formation of 8-OH-dG in calf thymus DNA was observed in the cells treated with RWFs in the presence of $H_2O_2$. On the other hand, chrysotile had no effect on the 8-OH-dG formation. 5. RWFs had no effect on the HGPRT point mutation and cell transformation. These results showed that RWFs could induce chromosomal damage, cell division disturbance and oxidative DNA damage in the RWFs treated cells.