• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.362-369
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• 2007

This paper was studied on the characteristics of acid resistance and thermal shock for epoxy coatings in the strong acidic environment. The exhaust gas system, such as a air preheater, desulfurization equipment, for industrial boiler is damaged by dew point corrosion. To protect the acid corrosion, the coating using nonmetal was applied. The electrochemical polarization test, acid resistance and thermal shock test for epoxy coatings were carried out. And the acid resistance and thermal shock characteristics, aspect, and electrochemical anti-corrosion characteristics for epoxy coatings in the strong acidic environment were considered. The main results are as followings: As the epoxy glass flake coating by acidic thermal shock was damaged to the crack, blistering and elution etc., the current density of epoxy glass flake coating is high. But the damage of epoxy metal complex coating by acidic thermal shock was not occurred. Therefore the characteristics of acid resistance and thermal shock for epoxy metal complex coating is better than those for epoxy glass flake coating.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.301-307
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• 2017

The planing hull is characterized by a large change in the posture according to the speed, and the shape of the propeller varies, so that the hull resistance varies greatly depending on the propeller used. Especially, the Savitsky system, which is widely used for estimating the resistance of planing hull, does not consider the characteristics of these propeller and ship bottom spray rails. In this paper, in order to investigate the difference in resistance characteristics between the propeller and the bottom of the propeller of 6m and 12m class propeller using propeller such as outboard or stern drive, A comparative test was conducted on resistance and attitude posture changes in the Circulating Water Channel of Institute of Medium & Small Shipbuilding. As a result of comparison test, it was confirmed that there is a clear difference in the attitude change due to the presence of the bottom floor spray rail and the change in resistance characteristics due to the installation of the propeller. However, attitude change with the propeller was found to be insignificant.

• Structural Engineering and Mechanics
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• v.83 no.6
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• pp.745-756
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• 2022

This study aims to determine the cause of the load resistance loss in storage racks that can be attributed to external forces such as earthquakes and to improve safety by developing reinforcement systems that can prevent load resistance loss. To this end, a static cyclic loading test was performed on pallet racks commonly used in logistics warehouses. The test results indicated that a pallet rack exposed to an external force loses more than 50% of its load resistance owing to the damage caused to column-beam joints. Three reinforcement systems were developed for preventing load resistance loss in storage racks exposed to an external force and for performing differentiated target functions: column reinforcement device, seismic damper, and viscoelastic damper. Shake table testing was performed to evaluate the earthquake response and verify the performance of these reinforcement systems. The results confirmed that, the maximum displacement, which causes the loss of load resistance and the permanent deformation of racks under external force, is reduced using the developed reinforcement devices. Thus, the appropriate selection of the developed reinforcement devices by users can help secure the safety of the storage racks.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.702-711
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• 1998

The characteristics of corrosion resistance for the surface of medium high carbon steels and low alloy steels utilizing as manufacturing the machinery structures and machining tools and treating by plasma/ion nitriding process have been studied in terms of electrochemical polarization behav-iors including corrosion potential(Ecorr) anodic polarization trends and polarization resistance(Rp) The seven base materials showed a clear passivation behavior for the polarization tests in the ASTM standard solution 1N ${H_2){SO_4}$ Although the treated surface by plasma nitriding for the seven test materials showed a significant increase in hardness the treatment gave a detri-mental effect in corrosion resistance. The various characteristics including corrosion potential polarization curves microstructures corrosion current polarization resistance among non-treat-ed nitriding and/or soft-nitriding treated specimens have been investigated and some of the mechanisms discussed.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.89-96
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• 1999

The base metal and weld metal of alloy designed austenitic stainless steels were electrochemically tested in artificial sea water. Pitting resistance of 14 different stainless steels was evaluated by measuring pitting potential. The effect of alloy element to pitting potential was evaluated by changing chromium, nickel, sulfur content. The site of pitting initiation was observed by optical microscope. As a result of electrochemical test, pitting resistance of weld metal was higher than base metal, and rapidly cooled weld metal has higher pitting potential than slowly cooled weld metal. In case of primary δ-ferrite solidification, pitting potential was increased, but residual δ-ferrite was detrimental to pitting resistance. Chromium was more effective to pitting resistance than nickel, and sulfur was very detrimental element to pitting resistance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1183-1189
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• 2010

Shock-resistance test for a real equipment for a normal vessel is one of the difficult problem in many cases because of terrible cost and weight. An analysis technique to evaluate the shock resistance in a design stage is necessary, instead In this paper, the process to evaluate the shock resistance of a propulsion motor for naval vessels was presented based on German navy's BV043 regulation. The shock signal to impose the equipment under the test was first evaluated, and was then applied to the structural FE model of the equipment. From the transient FEA, the time history of von-Mises stress was obtained by the mode superposition method. The shock resistance was evaluated using the peak value of the von-Mises stress.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1003-1008
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• 1995

CVD-Si3N4/CVD-SiC/pack-SiC/pyro-carbon/(3-D C/C composite) multilayer coating was performed to improve the oxdiation resistance and erosion resistance properteis of the 3-D carbon/carbon composite, and the plasma test was performed to measure the oxidation resistance and erosion resistance properties. The thicknesses of each film layer were about 10${\mu}{\textrm}{m}$ for pack-SiC, 5${\mu}{\textrm}{m}$ for CVD-SiC and 40${\mu}{\textrm}{m}$ for CVD-Si3N4. When the multilayer coated specimen was exposed to the plasma flame with temperature of 500$0^{\circ}C$ for 20 seconds, it showed the weight loss five times less than that of the only pyro-carbon coated specimen.

• KSBB Journal
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• v.13 no.4
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• pp.383-390
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• 1998

Bacillus subtilis DT134 was resistant to 50-fold higher concentration of cadmium ions (Cd2+) than cadmium-sensitive B. subtilis BD224 in Luria Broth (LB) medium. Minimal inhibition concentration test in LB agar plates also showed similar results. The elevated cadmium resistance of B. subtilis DT134 strongly suggested a possible existence of cadmium resistance gene in it. Southern blot with Staphylococcus aureus cadA gene fragment (757 bp NlaIV-XmnI cadA DNA fragment) as probe was carried out to test the existence and similarity of the gene. In high stringency condition, there was no detectable signal, but in low stringency, a strong signal specific to the cadA probe could be detected. These results strongly suggested that there was some similarity between total DNA of B. subtilis DT134 and S. aureus pl258 in terms of cadmium resistance gene and the resistance mechanism might be an efflux mechanism. The subsequent efflux experiment showed that the cadmium resistance mechanism of B. subtilis DT134 was also due to the efflux of cadmium.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.143-148
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• 2011

This study analyzes the resistance spot weldability of DP60 steels. To analyze the resistance spot weldability of DP60 steels, tensile strength test and macro-section test were conducted for the resistance spot welds. Acceptable welding conditions were determined as a function of the resistance spot welding process parameters such as electrode force, welding time, and welding current. The lower limit of the welding lobe was the minimum shear tension strength for 590MPa-grade steel while the upper limit was determined whether or not expulsion was detected.

• KIEAE Journal
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• v.7 no.4
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• pp.119-126
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• 2007

In this study, we processed two procedures of application test of filler for fire-resistance utility that are new application methods of aerated concrete and properties test of aerated concrete according to mixing ratio because we investigated the better use of aerated concrete as filler for fireproof safety and we proposed basic data about standardization of mixing of aerated concrete. We measured flow and volume change of aerated concrete. And if its volume doesn't change, we added measuring unit weight and compressive strength. To test application of aerated concrete as filler for fireproof safety, we filled up aerated concrete to fireproof safety according to suitable mixing ratio. Then we measured maximum temperature of inner part of fireproof safety in accordance with the standard test of fireproof. According to the results, aerated concrete as filler for fireproof safety could be possibly used. So when we make aerated concrete, we should consider using an adding agent as well as a foaming agent.