• Title/Summary/Keyword: erosion test

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Development of the Forest Road Cut-slope Rehabilitation Techniques Using Gabion Systems with Vegetation Base Materials (식생기반재 돌망태를 이용한 임도비탈면 복원기술 개발)

  • Park, Jae-Hyeon;Jeong, Yong-Ho;Choi, Hyung-Tae
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.11 no.5
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    • pp.92-103
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    • 2008
  • Development of new approaches to achieve naturally good ecological potential of forest road cut-slope by making the best use of advantages of gabion systems with vegetation base materials to prevent slope failure and erosion, in the area with highly erodible soil. As a result on the type analysis of gabion systems already installed in road cut-slopes, gabion systems were generally established to prevent slope failure. Existing gabion systems can be divided into monolithic and modular system and can be divided into ten subtypes according to the purpose of establishment and combination of other measures. As a result on the monitoring of erosion amount from forest road cut-slopes in the test applications, the order of erosion amount from largest to smallest is as follows : the curved road cut-slope site where normal gabion system was established ($7,911cm^3$); the control site ($7,632cm^3$); the straight road cut-slope site where normal gabion system was established ($7,301cm^3$); the curved road cut-slope site where the new gabion system was established ($5,684cm^3$); and the straight road cut-slope site where the new gabion system ($5,325cm^3$). Therefore, the result shows that the new gabion system is more effective than the normal gabion system to reduce erosion amount from forest ! road cut-slopes. During the study period, vegetation coverages of the straight and curved road cut-slope site where the new gabion system was established were about 45% and about 36%, so average vegetation coverage of the sites where the new gabion systems was established was higher than the sites where the normal gabion systems was established. Therefore, it was concluded that the new gabion system can be more effective for cut-slope revegetation.

Biomechanical behavior of CAD/CAM cobalt-chromium and zirconia full-arch fixed prostheses

  • Barbin, Thais;Silva, Leticia Del Rio;Veloso, Daniele Valente;Borges, Guilherme Almeida;Presotto, Anna Gabriella Camacho;Barao, Valentim Adelino Ricardo;Groppo, Francisco Carlos;Mesquita, Marcelo Ferraz
    • The Journal of Advanced Prosthodontics
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    • v.12 no.6
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    • pp.329-337
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    • 2020
  • PURPOSE. To verify the influence of computer-aided design/computer-aided manufacturing (CAD/CAM) implant-supported prostheses manufactured with cobalt-chromium (Co-Cr) and zirconia (Zr), and whether ceramic application, spark erosion, and simulation of masticatory cycles modify biomechanical parameters (marginal fit, screw-loosening torque, and strain) on the implant-supported system. MATERIALS AND METHODS. Ten full-arch fixed frameworks were manufactured by a CAD/CAM milling system with Co-Cr and Zr (n=5/group). The marginal fit between the abutment and frameworks was measured as stated by single-screw test. Screw-loosening torque evaluated screw stability, and strain analysis was explored on the implant-supported system. All analyses were performed at 3 distinct times: after framework manufacturing; after ceramic application in both materials' frameworks; and after the spark erosion in Co-Cr frameworks. Afterward, stability analysis was re-evaluated after 106 mechanical cycles (2 Hz/150-N) for both materials. Statistical analyses were performed by Kruskal-Wallis and Dunn tests (α=.05). RESULTS. No difference between the two materials was found for marginal fit, screwloosening torque, and strain after framework manufacturing (P>.05). Ceramic application did not affect the variables (P>.05). Spark erosion optimized marginal fit and strain medians for Co-Cr frameworks (P<.05). Screw-loosening torque was significantly reduced by masticatory simulation (P<.05) regardless of the framework materials. CONCLUSION. Co-Cr and Zr frameworks presented similar biomechanical behavior. Ceramic application had no effect on the biomechanical behavior of either material. Spark erosion was an effective technique to improve Co-Cr biomechanical behavior on the implant-supported system. Screw-loosening torque was reduced for both materials after masticatory simulation.

Study on Improvement of Mechanical Property, Oxidation and Erosion Resistance of SiC Matrix Ceramic Composites Reinforced by Hybrid Fabric Composed of SiC and Carbon Fiber (탄화규소섬유와 탄소섬유 하이브리드 직물을 강화재로 한 SiC 매트릭스 세라믹복합재의 기계적물성, 산화 및 삭마 저항성 개선 연구)

  • Yoon, Byungil;Kim, Myeongju;Kim, Jaesung;Kwon, Hyangjoo;Youn, Sungtae;Kim, Jungil
    • Composites Research
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    • v.32 no.3
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    • pp.148-157
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    • 2019
  • In this study, $C_f/SiC$, $SiC_f/SiC$ and $C_f-SiC_f/SiC$ ceramic composites reinforcing carbon fiber, SiC fiber and hybrid fiber were fabricated by hybrid TGCVI and PIP process. After the thermal shock cycle, 3-point bending and Oxy-Acetylene torch test, their mechanical behavior, oxidation and erosion resistance were evaluated. The $C_f/SiC$ composite showed a decrease in mechanical property along with increasing temperature, a pseudo-ductile fracture mode and a large quantity of erosion. The $SiC_f/SiC$ composite exhibited stronger mechanical property and lower erosion rate compared to the $C_f/SiC$, but brittle fracture mode. On the other hand, hybrid type of $C_f-SiC_f/SiC$ composite gave the best mechanical property, more ductile failure mode than the $SiC_f/SiC$, and lower erosion rate than the $C_f/SiC$. During the Oxy-Acetylene torch test, the $SiO_2$ formed by reaction of the SiC matrix with oxygen prevented further oxidation or erosion of the fibers for $C_f-SiC_f/SiC$ and $SiC_f/SiC$ composites particularly. In conclusion, if a hybrid composite with low porosity is prepared, this material is expected to have high applicability as a high temperature thermo-structural composite under high temperature oxidation atmosphere by improving low mechanical property due to the oxidation of $C_f/SiC$ and brittle fracture mode of $SiC_f/SiC$ composite.

THE TRACKING CHARACTERISTICS BY THE DIFFERENT CROSSLINKED DENSITY OF SILICONE RUBBER MATERIAL USED FOR OUTDOOR INSULATION (옥외용 실리콘 고무재료의 가교도에 따른 내트랙킹 특성)

  • Kim, D.W.;Lee, C.Y.;Hong, J.Y.;Baek, J.H.;Lee, S.J.
    • Proceedings of the KIEE Conference
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    • 1995.07c
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    • pp.1058-1060
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    • 1995
  • In this paper, we studied the tracking characteristics of silicone rubbers that differed in the degree of crosslinking. As the tracking method, we adopted ASTM D 2303 and Merry-Go-Round(MGR) test method. It was found that the higher the degree of crosslinking, the better tracking characteristics. In these two test methods, specimens showed similar tendency of performance variation according to the degree of crosslinking. However the degradation phenomena were very different. As for MGR method, only the color of specimens' surface changed without any erosion or tracking path on them. On the contrary, the specimens subjected to ASTM D 2303 test method showed severe erosion.

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Cavitation Damage Behavior for 431 Stainless Steel by Hybrid Test in Sea Water (해양 환경 하에서 431 스테인리스강의 하이브리드 실험을 통한 캐비테이션 손상 거동)

  • Chong, Sang-Ok;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.46 no.6
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    • pp.271-276
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    • 2013
  • The demand for stainless steel is continuously increasing with the development in offshore industry due to its excellent corrosion resistance characteristics. However, it suffers cavitation-erosion in application of high rotating fluid and the damage accelerates in combination with electrochemical corrosion because of Cl-ion in sea water. This paper investigated the complex damage behavior for 431 stainless steel, that is one of martensite stainless steels, through the hybrid test in sea water. Various experiments were carried out, including potential measurement, anodic/cathodic polarization experiment and Tafel analysis. Surface morphology was observed and damage depth was analyzed by SEM and 3D microscope after each experiment, respectively. The results revealed that more active potential was observed under cavitation condition than static condition due to breakdown of passive film and activation of charge transfer, and that higher corrosion current density was obtained under cavitation condition due to synergistic effect of corrosion and erosion.

Ablative Properties of 4D Carbon/Carbon Composites by Combustion Test

  • Park, Jong-Min;Ahn, Chong-Jin;Joo, Hyeok-Jong
    • Carbon letters
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    • v.9 no.4
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    • pp.316-323
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    • 2008
  • The factors that influence ablation resistance in fiber composites are properties of the reinforced fiber and matrix, plugging quantity of fiber, geometrical arrangement, crack, pore size, and their distributions. To examine ablation resistance according to distribution of crack and pore size that exist in carbon/carbon composites, this study produced various sizes of unit cells of preforms. They were densified using high pressure impregnation and carbonization process. Reinforced fiber is PAN based carbon fiber and composites were heat-treated up to $2800^{\circ}C$. The finally acquired density of carbon/carbon composites reached more than $1.932\;g/cm^3$. The ablation test was performed by a solid propellant rocket engine. The erosion rate of samples is below 0.0286 mm/s. In conclusion, in terms of ablation properties, the higher degree of graphitization is, the more fibers that are arranged vertically to the direction of combustion flame are, and the less interface between reinforced fiber bundle and matrix is, the better ablation resistance is shown.

Antioxidant Effects of GaMiHyangSaYukGunJaTang against Gastric Mucosal Lesions induced by Indomethacin (가미향사육군자탕(加味香砂六君子湯)의 Indomethacin 유도 위점막손상 에 미치는 항산화효과(抗酸化效果))

  • Kim, Kyung-Sun;Shin, Heung-Mook
    • The Journal of Korean Medicine
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    • v.19 no.1
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    • pp.165-178
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    • 1998
  • This study was carried out to investigate the protective effects of GaMiHyangSaYukGunJaTang on gastric mucosal lesions caused by indomethacin in rats.The test group was injected with indomethacin after the oral administration of GaMiHyangSaYukGunJaTang, while the control group was injected only with indomethacin. The lipid peroxidation level increased considerably in the control group, but superoxide disnurtase(SOD), catalase and glutathione(GSH) levels remarkably decreased. The following effects induced by indomethacin were observed in the stomach of the control group; mucosa hemoIThagic infarct, mucosa cell necrosis, leukocyte appearance, mucosa hemorrhagic erosion and gastric pit disawearance. In the test group, lipid peroxides level was significantly reduced compared with the control group While SOD, catalase and GSH levels considerably increased. The following effects were also observed in the stomach of the test group; mucosa hemorrhagic infarct, mucosa cell necrosis, leukocyte appearance and mucosa hemorrhagic erosion occured far less and gastric pit disappearance was not observed at all. This results suggest that GaMiHyangSaYukGunJaTang is effective in the remedy of gastric mucosal lesions as GaMiHyangSaYukGunJaTang suppresses the production of the lipid peroxides and free radicals induced by indomethacin and activates SOD, catalase and GSH.

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Tracking Resistance of Epoxy Mold Insulating Materials by the Rotating Wheel Dip Test (회전윤법에 의한 에폭시 몰드 절연재료의 내트래킹성 평가)

  • Cho, Han-Goo;Yun, Mun-Su;Park, Yang-Kwan
    • Proceedings of the KIEE Conference
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    • 2000.07c
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    • pp.1590-1592
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    • 2000
  • The time to tracking breakdown of treated filled specimen is longer than untreated filled specimen. And, after the RWDT, the surface of specimen by adding untreated filler appeared heavy erosion. It was found that the addition to surface treated filler. the better tracking resistance. In the RWDT, the breakdown specimen is not affected by the dry flashover voltage. despite the fact that the surface degradation of tracking test has different state on each specimen. This suggests that wet flashover voltage play an important role in evaluating of tracking and erosion on the surface degradation in tracking test. And, the flashover voltage of specimen under wet conditions are greatly affected by the salt concentration and degree of degradation by the RWDT. Because of hydrophobicity and degree of degradation by the RWDT, the flashover voltage of treated filled specimen is higher than that of untreated filled specimen. Different types of specimen may have different hydrophobicity and their surface state under contaminated conditions may not be the same. It is assumed that this phenomenon is related to the decrease in hydrophobicity of the surface of the materials.

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Cavitation Test at High Reynolds Number Using a Partial Propeller Blade Model (부분 프로펠러 날개 모형을 이용한 높은 레이놀즈 수에서의 공동시험)

  • Choi, Gil-Hwan;Chang, Bong-Jun;Cho, Dae-Seung
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.6
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    • pp.569-577
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    • 2009
  • As the scale factor of model propellers utilized in cavitation test is about 40, it is difficult to find out practical countermeasures against the small area erosions on the blade tip region throughout model erosion tests. In this study, a partial propeller blade model was used for the observation of cavitation pattern for the eroded propeller. A partial propeller blade model was manufactured from 0.7R to tip with expanded profile and with adjustable device of angle of attack. Reynold's number of a partial propeller blade model is 7 times larger than that of a model propeller. Also, anti-singing edge and application of countermeasures to partial propeller blade model which produced in large scale can be more practical than a model propeller. For the observation of cavitation at high Reynold's number, high speed cavitation tunnel was used. To find out the most severe erosive blade position during a revolution, cavitation observation tests were carried out at 5 blade angle positions.

Void Detection Under Concrete Pavement Using Nondestructive Testing (비파괴시험을 통한 콘크리트포장 하부 공동조사)

  • 유택석;한승환
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.781-786
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    • 1999
  • One of the major causes of concrete pavement deterioration is the loss of support due to erosion and pumping of subbase and subgrade. In this study, procedures for the detection of voids under concrete pavement slab are presented using nondestructive test method such as FWD(Falling Weight Deflectometer) and GPR(Ground Penetration Radar). The deflection responses of concrete slab obtained in FWD field test are analysed for determining the presence of void. Also, reflection responses in GPR test are interpreted. It was concluded that these procedures are available for detecting the viods under concrete pavement slab.

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