• Tribology and Lubricants
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• v.25 no.3
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• pp.171-175
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• 2009

One of the critical issues associated with the 40mm long hollow cylinder's development and maintenance is the prediction of cylinder erosion. The actual firing test is the most accurate method to measure the cylinder erosion rate. But it costs a great deal and requires a long measurement time. Hence many empirical methods have been proposed to predict the erosion rate and life span of long hollow cylinders. An EFC formula is calculated. An approximate erosion formula for the ammunition type A is derived to interpolate 16 observation values up to 4,000 rounds. A new erosion equation and muzzle velocity formula are also suggested. Several numerical results are presented.

• Journal of Fisheries and Marine Sciences Education
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• v.11 no.2
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• pp.139-149
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• 1999

Thermal sprayed Ni-Cr alloy coating on the carbon steel was carried out erosion-corrosion test and electrochemical corrosion test in the marine environment. The erosion-corrosion behavior and electrochemical corrosion characteristics of substrate(SS400) and thermal sprayed Ni-Cr coating was investigated. The erosion-corrosion control efficiency of Ni-Cr coating to substrate was also estimated quantitatively. The main results obtained are as follows : 1) The weight loss rate of Ni-Cr coating layer by the erosion-corrosion compared with substrate was smaller. With the lapse of time, the weight loss rate of substrate was linearly increased in $25{\Omega}{\cdot}cm$ solution, but that of Ni-Cr coating became stable. 2) The corrosion potential of substrate became less noble than that of Ni-Cr coating layer, and the corrosion current density of Ni-Cr coating became lower than that of substrate. 3) The control efficiency of erosion-corrosion of Ni-Cr coating compared to substrate became more dull than that of corrosion in $25{\Omega}{\cdot}cm$ and $5000{\Omega}{\cdot}cm$ solution.

• Journal of dental hygiene science
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• v.12 no.6
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• pp.696-701
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• 2012

The purpose of this study was to determine pH value of some alcoholic drinks sold in Korea and to provide the basic information which can cause dental erosion. Alcoholic drinks commercially sold were purchased from various big markets in Korea. The sorts of drinks tested in this study consisted of 5 brands of beers, 24 brands of makgeollis, 9 brands of wines and 12 brands of sojus. The test groups were selected randomly and the pH of each beverage was determined using a pH meter he each pH was measured. For statistical data, Mann-Whitney test was used to analyze difference for red wine and white wine and Kruskal-Wallis test was used to compare the pH of each test group. The result of this study was as followings: the mean pH of 5 brands of beers was 4.21, that of 24 brands of makgeollis 3.88, of 9 brands of wines 3.34 and of 12 brans of sojus 7.86. Each test group was significantly different (p<0.05). Except for soju groups, the test groups had a low pH value which can cause dental erosion. In terms of comparing between pH value of red wine and white wine, the result of this study represented that the mean pH of red wine was 3.45 and that of white wine was 3.21. This result showed the pH of two kinds of wine had a low pH which can lead to dental erosion and the difference of two wine were significantly different (p<0.05). As a result, some drinks sold in Korea have a high erosive potential on teeth since they have a comparatively low pH expect soju. Hence, when we consume some kinds of alcoholic drinks, we make sure to remember that the alcoholics which had a low pH, can have an effect on dental erosion that mean we should avoid to drink some alcoholic drinks with low pH for long time.

• Tribology and Lubricants
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• v.9 no.1
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• pp.55-61
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• 1993

Recently, due to the erosion damage that were generated increasingly at alloy metals of slide bearing by cavity of lubricating oil with tendency of high speed and high output of reciprocating engine, there is a need to study the process on the formation of cavitation erosion, and the characteristic of cavitation erosion at lubricating oil environments under various condition for marine ship. Therefore, the apparatus of cavitation erosion experiment used 20 KHz, $24 \mu m$ piezoelectric vibrator. The main results obtained through this test method are as follows: 1. The max. erosion rate at lubricating oil environments was related to the change of space, oil film thickness, and shown to tendency of gear oil>system oil>turbine oil>mixed oil environments with different viscosity. 2. The pitted hole by cavitation erosion at high viscosity oil environments became small and deep, and in addition to, they appeared to be wide and shallow at low viscosity.

• Journal of the Korean institute of surface engineering
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• v.35 no.6
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• pp.371-376
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• 2002

Steam turbine components of power generators are subjected to severe damages from the particle erosion by iron oxides (mainly $Fe_3$$O_4$) which are formed due to the oxidation of boiler tubes, causing high costs for maintaining and repairing. One of the practical ways to minimize the particle erosion is to apply the erosion resistant boride coating on the turbine components which is composed of boride apply. But the evaluation of its performance has not been carried out. A particle erosion tester, which can offer the erosion condition of steam turbine components, was developed to evaluate the performances of the boronized Cr/Mo alloy. The result showed that the boronized Cr/Mo alloy showed superior resistance to particle erosion to the bare Cr/Mo alloy in all test conditions.

• Journal of Welding and Joining
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• v.10 no.4
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• pp.181-189
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• 1992

The purpose of this investigation is to examine the effects of the strengthening treatments on the mechanical properties of the flame-sprayed titania ceramic coating layer. The strengthening treatments for flame sprayed specimens were carried out in 12 different conditions in vaccum furance. The mechanical properties such as microhardness, thermal shock resistance, adhesive strength and erosion resistance were tested for the sprayed specimens after strengthening treatments. And it was clear that the mechanical properties of coating layer were much improved by the strengthening treatments. The results obtained are summarized as follows; 1. It was shown that the metallurgical bond was formed between substrate and coating layer by the strengthening treatments and that thermal shock resistance and adhesive strength were remarkably raised. 2. Microhardness of coating lay was considerably increased by the strengthening treatments. 3. Erosion resistance and porosity of coating layer were slightly improved by the strengthening treatments.

• Tribology and Lubricants
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• v.11 no.1
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• pp.58-65
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• 1995

When marine lubricating oil began to be emulsified and oxidized through ingressive water that have leaked from cooling pump seal systems, cooler, purifier system and piping system, the cavitation erosion-corrosion in alloy metals of bearings remains to the various troublesome problem at effective engine performance. Therefore, applied the cathodic protection to the control test of cavitation erosion-corrosion, and appointed the marine system oil containing 3% sea water as test environments, with different conductibility. Also, used the piezoelectric vibrator with 20 KHz, 24 $\mu$m as the cavity generation apparatus, and examined the weight loss, potential value, current density etc. in specimens with those condition. According to this testing data, investigated influence of cathodic protection on the control characteristics of cavitation erosion-corrosion, and will serve those as an elementary design data of marine bearing.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.1 no.1
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• pp.133-140
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• 1998

The following conclusions are based upon data collected and visual observations made during the performance of the tests : 1. The performance of the erosion control products tested was for a particular set of conditions, and may be expected to differ if any or all of the test parameters were to be changed. If even just one parameter is changed from one test to the next, the results can be expected to be different. 2. Due to the fact that only two replications of each product were tested, we believe that the results presented herein are indicative only and not conclusive. 3. The ECB SC produced the least amount of soil erosion followed by ECB S, ECB C, and Coir No. 2, in that order. 4. All of the erosion control blankets tested significantly reduced soil erosion rates with respect to the bare soil controls. 5. The ECB S produced the smallest water runoff rate, followed closely by ECB SC. Next in order were ECB C and Coir No. 2. 6. All of the erosion control blankets reduced the water runoff rate with respect to the bare soil control. 7. Mesh 2cm There was not much difference in plant height for the four erosion control blankets and the bare soil control plots. the ECB S produced slightly taller plants than the rest of the materials tested. 8. The four erosion control blankets(ECB C, ECB SC, ECB S, and Coir No. 2) produced a larger plant mass than the bare soil plots. The difference between the plant mass for the four erosion control blankets, however, is minimal. 9. The ECB C produced the least percentage of lost seed and the largest percentage of germinating seed. 10. The ECB SC had the second smaller percentage of seed lost, followed closely by ECB S, and then by Coir No. 2. 11. All erosion control blankets had a smaller percentage of seed lost than the bare soil control plots. 12. The ECB C had the second largest percentage of germinating seed, followed closely by ECB SC and Coir No. 2. 13. All erosion control blankets had a larger percentage of germinating seed than the bare soil control plots. 14. The ECB C had the smallest percentage of non-germinating seed, followed by ECB S, Coir No. 2, and ECB SC, in that order. 15. All erosion control blankets had smaller percentages of non-germinating seed than the bare soil control plots.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.61-68
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• 2019

Only the power is converted from AC to DC, in accordance with IEC 60587 based test method, in order to develop the LSR(Liquid Silicone Rubber) insulator material for HVDC, the experiment of Inclined Plate Tracking and Erosion Resistance was conducted. A contaminant (2.5 mS/cm: ammonium chloride) was applied at a rate of 0.3 ml/min and a voltage of ${\pm}3.5kV$, and was evaluated on the basis of 60 mA/2s. The samples were prepared by dispersing LSR/Nano silica_25wt% Composites in LSR. The erosion phenomena of surface discharge and tracking due to DC polarity and negative polarity were measured by image, leakage current maximum and thermal camera. The thermal imaging camera measured the surface temperature generated by the joule heat of the leakage current due to the drying discharge and the conductive current. After the measurement, the tracking and erosion mechanisms were evaluated for erosion weight, erosion depth and erosion length. Positive and negative polarity of LSR/Nano Silica_25wt% composite Tracking and erosion results show that positive polarity is more severe than negative polarity.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.31-37
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• 2023

In the present study, a method of performing cavitation erosion test directly on the anodized surface of the rudder model is proposed, not applying ink or paint on its surface. An image processing technique is newly developed to quantitatively evaluate the erosion damages on the rudder model surface after erosion test. The preprocessing saturation image, image smoothing, adaptive hysteresis thresholding and eroded area detection algorithms are in the image processing program. The rudder cavitation erosion tests are conducted in the rudder deflection angle range of 0° to -4°, which is used to maintain a straight course at the highest speed of the targeted navy ship. In the case of the conventional flat-type full-spade rudder currently being used in the target ship, surface erosion can occur on the model rudder surface in the above rudder deflection angle range. The bubble type of cavitation occurs on rudder surface, which is estimated to be the main reason of erosion damage on the rudder surface.