• 드라이브 ㆍ 컨트롤
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• 제19권1호
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• pp.8-15
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• 2022

The demand for the re-painting of steel bridges is increasing, but surface treatment is still centered on human resources for on-site re-painting processes. Worker safety accidents continue to occur because the work is performed in a narrow space. Recently, PS balls with excellent surface treatment have been used for blasting, but the working environment is poor due to the large amount of dust generated. In this study, an effective surface treatment method using impeller blasting equipment was developed. The correlation between steel ball size, impeller rotation speed, and exposure time was studied to optimize the efficiency of the surface treatment.

• 한국강구조학회 논문집
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• 제20권5호
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• pp.583-590
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• 2008

강구조물의 제작에는 흑피 등의 이물질 제거 및 도장의 부착성 증대를 위해 블라스트 표면처리가 실시되고 있지만, 이러한 도장용 블라스트 처리가 용접이음의 피로거동에 미치는 영향에 대해서는 검토되어 있지 않은 실정이다. 이에 본 논문에서는 강교 도장용 블라스트 처리가 용접이음부의 피로거동에 미치는 영향을 검토하기 위하여, 용접한 그대로 및 용접 후 블라스트 처리한 면외거셋 용접이음을 대상으로 피로실험을 실시하였다. 그 결과, 강교 도장용 블라스트 처리에 의해 면외거셋 용접이음의 용접지단부 비드접선각도 및 곡률반경이 증가되고 압축잔류 응력이 도입됨을 확인하였다. 그리고 면외거셋 용접이음의 피로수명은 고응력범위에서는 블라스트 처리의 유무와 상관없이 거의 동일하였지만, 저응력범위(150MPa이하)에서는 피로수명이 증가하였으며, 피로한계는 약 160%정도로 크게 증가함을 확인하였다.

• Smart Structures and Systems
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• 제21권5호
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• pp.561-569
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• 2018

Ground vibration is one of the most undesirable effects induced by blast operation in mountain tunnels, which could cause negative impacts on the residents living nearby and adjacent structures. The ground vibration effects can be well represented by peak particle velocity (PPV) and corner frequency ($f_c$) on the ground. In this research, the PPV and the corner frequency of the mountain surface above the large-span tunnel of the new Badaling tunnel are observed by using the microseismic monitoring technique. A total of 53 sets of monitoring results caused by the blast inside tunnel are recorded. It is found that the measured values of PPV are lower than the allowable value. The measured values of corner frequency are greater than the natural frequencies of the Great Wall, which will not produce resonant vibration of the Great Wall. The vibration effects of associated parameters on the PPV and corner frequency which include blast charge, rock mass condition, and distance from the blast point to mountain surface, are studied by regression analysis. Empirical formulas are proposed to predict the PPV and the corner frequency of the Great Wall and surface structures due to blast, which can be used to determine the suitable blast charge inside the tunnel.

• Journal of Periodontal and Implant Science
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• 제37권3호
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• pp.599-611
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• 2007

The present study was performed to evaluate the surface roughness and effect of Tetracycline-HCI on the change of implant surface microstructure according to application time. Ti$O_2$ surface Implant was utilized. Implant surface was rubbed with 50mg/ml Tetracycline-HCI solution for 0.5min, 1min, 1.5min, 2min, 2.5min and 3min respectively in the Tetracycline-HCI group. Then, specimens were measured surface roughness and processed for scanning electron microscopic observation. The results of this study were as follows. 1. Ti$O_2$ blast implant surface showed increased surface roughness 1.5 minute after treatment with Tetracycline-HCI. But, there were not significant differences in saline group after treatment. 2. Tetracycline-HCI group showed changed surface micro-morphology in SEM after 1.5 minute. There were not significant differences in saline group after treatment. 3. Between Tetracycline-HCI group and saline group, there were difference in surface roughness change and SEM micro-morphology. Tetracycline-HCI have influence on Ti$O_2$ blast implant surface. In conclusion, the detoxification with 50mg/ml Tetracycline-HCI must be applied respectively with different time according to various implant surfaces.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.251-253
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• 2017

Prefilming air blast 연료노즐의 다상유동 해석을 수행하였다. 연료가 미립화되는 과정을 관찰하였으며 liquid film의 두께와 속도를 계산하였다. Slot에서 분사된 연료는 prefilmer surface에서 얇은 액막을 형성한 후 연료노즐 lip에서 액적으로 분열되었다. 또한 계산된 liquid film의 두께와 속도를 경계조건으로 하여 반응유동장 해석을 수행하였다. 분사된 액적은 venturi throat를 지나면서 기화되었고 연료노즐 하류에 반응영역이 형성되어 안정적으로 보염이 이루어졌다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.463-470
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• 2000

In tunnel excavation by blast beneath the surface structures in urban area, the characteristics of ground vibration induced by blast and its influence on surface structures are analyzed by the field test and the numerical analysis on dynamic behaviors of the structure. According to the field test on the propagating characteristics of blast vibration through the rock mass and the concrete foundation pile. the attenuation index of peak particle velocity with distance shows the range of 1.7∼2.0 for the rock mass and the range of 2.0∼2.3 for the concrete pile. This shows that the blast vibration reduces more rapidly in the concrete pile. It is known from the numerical analysis on dynamic behavior of the structure that the coefficient of response, velocity ratio of structure response to input wave, is different according to the story of the structure. It can be said from this research that the characteristics of the ground vibration and the dynamic behavior of the structure should be well evaluated and be considered as important factors for safe blasting design especially in underground excavation at shallow depth in urban area.

• The Plant Pathology Journal
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• 제16권3호
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• pp.147-150
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• 2000

Sporulation patterns of rice blast fungus were studied at relatively later stages of leaf blast and neck blast seasons in Icheon, Korea. This experiment was done by detaching lesion-bearing leaves and panicle bases. The number of conidia remaining on the leaf blast lesions of different cultivars from Jul 20 to Jul 23 ranged from 3,640 to 82,740 spores. More conidia were observed on the adaxial surface because they were released from abaxial surface. After heading, sporulation was observed from the lesions on the flag leaves but the number of spores was less than in the late July. Detached panicle bases or uppermost internodes infected by Pyricularia grisea produced abundant amount of conidia. Among these panicle bases, 30.1 mm size lesion recorded the highest count of 244,560 spores. When we compared the sporulation amount using the KY-type spore trap, more conidia were recorded from intact lesions than from the lesions which removed conidia and conidiophore The ratio of conidia release against total sporulation ranged from 20.5%-25.0% for leaf blast and 8.2%-25.3% in the neck blast. Effective inoculum potential was also discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.273-274
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• 2010

본 연구에서는 고로슬래그의 초기 강도의 증진과 응결지연의 단점을 개선하기 위해 고로 슬래그 및 석고가 혼입된 고로 슬래그를 대상으로 pH 변화에 따른 고로 슬래그의 표면 활성화의 특성과 quick-setting 특성에 관하여 연구하였다.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.243-250
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• 2018

The use of blast hardened bulkheads (BHBs) is an effective vulnerability hardening technique for improving the survivability of naval warships when internal explosions occur due to being shot by an anti-surface missile. In this paper, a new concept of BHBs reinforced by aluminum (Al) foam is proposed. The new concept can significantly reduce the blast pressures transferred to bulkheads and, unlike conventional BHBs, can be easily installed to operating naval warships. Chamber model blast tests were performed to demonstrate the effectiveness of the Al-foam BHBs and the results are further supported by numerical simulations. Finally, a practical preliminary is proposed for the Al-foam BHBs.

• Journal of Welding and Joining
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• 제20권4호
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• pp.551-556
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• 2002

Solid particle erosion wear characteristics of high Cr white iron hardfacing were investigated using the erosion wear test method according with the ASTM G76-95. Wear experiments, where the blast angle, blast distance and blast pressure were selected as test variables, were planned and analyzed by response surface method (RSM to evaluate the wear loss statistically and quantitatively. The measured wear losses well coincided with the calculated ones by the experimental equation. The wear loss of high Cr cast iron hardfacing was increased with blasting pressure, but affected in a complicated way by the blasting angle and distance. Erosion wear of high Cr cast iron hardfacing could be well predicted by RSM analysis of wear variables.