Correlation of the Sediment Properties and Erosion in Francis Hydro Turbine Runner

Ujjwal Shrestha,Zhenmu Chen,Young Do Choi 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.2

Sediment erosion is the main problem for the hydropower situated in South Asia and South America. Due to sediment erosion, hydropower in those areas cannot operate in their full potential. Sediment erosion is a significant problem in turbomachinery and associated with degradation of turbine performance. The sediment erosion removes the turbine material from its surface. It can cause fracture of the turbine, which leads to an economic loss. In this paper, the sediment properties and its influence on erosion have discussed. Sediment properties like shape, size, and concentration have a direct influence on erosion. The numerical analysis was conducted to visualize the erosion in Francis hydro turbine. The most vulnerable area for the sediment erosion in Francis hydro turbine has predicted. The precise prediction of the sediment erosion in the turbine is the difficult task due to the synergetic effect of sediment parameters (shape, size, concentration, hardness, velocity). The accurate and precise indication of the sediment erosion required both experimental and computational analysis. In this study, solid-fluid computational analysis has done to identify the susceptible area on runner blade and influence of sediment parameters on erosion.

SATEEC 시스템을 이용한 객토 토양의 토성고려에 따른 도암댐 유역의 토양유실 및 유사량 분석

유동선 ( Dongsun Yoo ),안재훈 ( Jaehun Ahn ),윤정숙 ( Jongsuk Yoon ),허성구 ( Sunggu Heo ),박윤식 ( Younshik Park ),김종건 ( Jonggun Kim ),임경재 ( Kyoung Jae Lim ),김기성 ( Ki-sung Kim ) 한국농공학회 2007 한국농공학회 학술대회초록집 Vol.2007 No.-

There have been serious soil erosion and water pollution problems caused by highland agriculture practices at Doam-dam watershed. Especially agricultural activities, chemical and organic fertilizer and pesticide applications, soil reconditioning to maintain soil fertility are known as primary causes of soil erosion and water qaulity degradation in the receiving water bodies. Among these, soil reconditioning can accelerate soil erosion rates. To develop soil erosion prevention practices, it is necessary to first estimate the soil erosion from the watershed. Thus, the Universal Soil Loss Equation (USLE) model has been developed and utilized to assess soil erosion. However, the USLE model cannot be used at watershed scale because it does not consider sediment delivery ratio (SDR) for watershed application. For this reason, the Sediment Assessment Tool for Effective Erosion Control (SATEEC) was developed to assess the sediment yield at any point in the watershed. The USLE-based SATEEC system can estimate the SDR using area-based SDR and slope-based SDR module. In this study, the SATEEC system was used to estimate soil erosion and sediment yield at the Doam-dam watershed using the soil properties from reconditioned agricultural fields. Based on the soil sampling and analysis, the USLE K factor was calculated and used in the SATEEC system to analyze the possible errors of previous USLE application studies using soil properties from the digital soil map, compared with that using soil properties obtained in this study. The estimated soil erosion at the Doam-dam watershed without using soil properties obtained in the soil sampling and analysis is 1,791,400 ton/year (123 ton/ha/year), while the soil erosion amounts is 2,429,900 ton/year (166.8 ton/ha/year) with the use of soil properties from the soil sampling and analysis. There is 35% increases in estimated soil erosion and sediment yield with the use of soil properties from soil reconditioned agricultural fields. Since significant amounts of soil erosion are known to be occurring from the agricultural fields, the soil erosion and sediment yield from only agricultural fields was assessed. The soil erosion rate is 45.9 ton/ha/year without considering soil properties from soil reconditioned agricultural fields, while 105.3 ton/ha/year after considering soil properties obtained in this study, increased in 129%. This study shows it is very important to use correct soil properties to assess soil erosion and sediment yield simulation. It is recommended that further studies are needed to develop environment friendly soil reconditioning method should be developed and implemented to decrease the speed of soil erosion rates and water quality degradation.

월단위 토양유실가능성 추정을 위한 ArcGIS 기반의 모형 개발

유나영,이동준,한정호,임경재,김종건,김기형,김소연,김은석,박윤식,Yu, Na Young,Lee, Dong June,Han, Jeong Ho,Lim, Kyoung Jae,Kim, Jonggun,Kim, Ki Hyoung,Kim, Soyeon,Kim, Eun Seok,Park, Youn Shik 한국농공학회 2017 한국농공학회논문집 Vol.59 No.1

Soil erosion has been issued in many countries since it causes negative impacts on ecosystem at the receiving water bodies. Therefore best management practices to resolve the problem in a watershed have been developed and implemented. As a prior process, there is a need to define soil erosion level and to identify the area of concern regarding soil erosion so that the practices are effective as they are designed. Universal Soil Loss Equation (USLE) were developed to estimate potential soil erosion and many Geographic Information System (GIS) models employ USLE to estimate soil erosion. Sediment Assessment Tool for Effective Erosion Control (SATEEC) is one of the models, the model provided several opportunities to consider various watershed peculiarities such as breaking of slope length, monthly variation of rainfall, crop growth at agricultural fields, etc. SATEEC is useful to estimate soil erosion, however the model can be implemented with ArcView software that is no longer used or hard to use currently. Therefore SATEEC based on ArcView was rebuild for the ArcGIS software with all modules provided at the previous version. The rebuilt SATEEC, ArcSATEEC, was programmed in ArcPy and works as ArcGIS Toolset and allows considering monthly variations of rainfall and crop growth at any watershed in South-Korea. ArcSATEEC was applied in Daecheong-dam watershed in this study, monthly soil erosion was estimated with monthly rainfall and crop growth variation. Annual soil erosion was computed by summing monthly soil erosion and was compared to the conventional approach to estimate annual soil erosion. The annual soil erosion estimated by the conventional approach and by summing monthly approach did not display much differences, however, ArcSATEEC was capable to provide monthly variation of soil erosion.

지방자치단체 출자출연기관 자본잠식에 관한 연구

임충혁,구도훈,정창훈 한국지방공기업학회 2022 한국지방공기업학회보 Vol.18 No.2

This study analyzes the capital erosion ratio and trend by dividing local government invested and contributed companies by type (by investment, contribution) using financial report data from the Ministry of Public Administration and Safety during 2014-2020. In 2020, 39 out of 92 invested companies, 39 (42.4%) had no capital erosion, 25 (27.2%) had more than 0% and less than 50%, 11 (12.0%) had more than 50% but less than 100%, and 7 (18.5%) had full capital erosion (100% and above). Therefore, there are 18 institutions with partial and complete erosion, with 19.5% of all invested companies suffering capital erosion. It seems necessary to determine the cause of capital erosion and prescribe for future capital erosion mitigation. In the case of contributed companies, 603 (90.1%) out of 669 total contributed companies in 2020, had no capital erosion. However, 43 companies (6.4%) suffer 0% and less than 50%, 10 (1.5%) of partial erosion, and 13 (1.9%) of 100% or more of full capital erosion. Therefore, 23 contributed companies (3.4%) are suffering from either partial or full capital erosion, which seems to be relatively good compared to invested companies. As a result of classifying and analyzing contributed companies by sub-type, the largest proportion of capital erosion companies (71%) is medical care center. The type with the highest proportion of institutions capital-infested after medical centers is credit guarantee companies (55%). Both types have the characteristic that the size of capital is relatively larger than other contributed companies. Conversely, the type with a low proportion of capital erosion is female youth institutions, only about 4% of institutions showing capital erosion. 본 연구에서는 행정안전부의 2014-2020 지방자치단체 출자출연기관 재무보고서 자료를 활용하여 전체 자치단체가 설립한 출자출연기관을 유형별로 (출자, 출연, 출연기관 종류별) 구분하여 자본잠식 비율 및 추세를 분석한다. 이들 출자출연기관의 자본잠식에 대한 현황 파악과 원인 규명은, 향후 이들 기관의 자본잠식완화에 대한 대처방안을 마련하는데 도움이 될 것으로 판단한다. 가장 최근 연도인 2020년의 경우, 전체 출자기관 92개 중에 자본잠식이 전혀 없는 기관은 39개 (42.4%)이고, 0% 이상 50% 미만은 25개 (27.2%), 부분잠식인 50% 이상 100% 미만은 11개 (12.0%), 그리고 완전자본잠식 상태인 100% 이상은 7개 (18.5%)로 나타났다. 따라서 부분잠식과 완전잠식인 출자기관이 18개로, 전체 출자기관의 19.5%가 자본잠식을 겪고 있는 것으로 나타나 이들 기관의 자본잠식에 대한 원인 규명 및 향후 자본잠식완화에 대한 처방이 필요한 것으로 보인다. 출연기관의 경우 2020년 전체출연기관 669개 중에 자본잠식이 전혀 없는 기관이 603개 (90.1%), 0% 이상 50% 미만은 43개 (6.4%), 부분잠식인 50% 이상 100% 미만은 10개 (1.5%), 그리고 완전자본잠식 상태인 100% 이상은 13개 (1.9%)로 나타났다. 따라서, 부분잠식과 완전자본잠식인 기관이 23개로 전체 출연기관의 3.4%가 자본잠식을 겪고 있는 것으로 나타나, 19.5%를 보이는 출자기관에 비해 출연기관의 자본잠식 상태는 아직은 상대적으로 양호한 것으로 보인다. 출연기관을 유형별로 분류해 분석한 결과, 가장 많은 자본잠식기관 비율 (71%)을 보이는 기관 유형은 의료원이다. 의료원 다음으로 자본잠식된 기관의 비율이 높은 유형은 신용보증으로, 신용보증기관의 약 55%가 자본잠식 상태인 것으로 확인된다. 이 두 유형 모두 자본의 규모가 여타의 출연기관에 비해 상대적으로 큰 기관이라는 특징을 가지고 있다. 반대로, 자본잠식 비중이 낮은 유형은 여성청소년 기관으로, 약 4%의 기관만이 자본잠식상태를 보인다.

A Survey on the Prevalence and Risk Indicators of Dental Erosion among 13-15 Year Old Adolescents in Yangsan, Korea

노태환,이금랑,김지연,김신 大韓小兒齒科學會 2016 大韓小兒齒科學會誌 Vol.43 No.3

최근 세계적으로 치아침식증에 대한 관심이 급증하고 인식의 변화가 나타나 많은 연구보고가 있었다. 우리나라 국민건강영양조사에 따르면 청소년기로 갈수록 1일 탄산음료 섭취량이 늘고 있는 추세이며, 이는 청소년들이 치아침식증에 취약할 수있음을 시사한다. 하지만 우리나라에서는 이에 대한 인식이 아직 미진하고, 치과계에서도 연구적, 임상적 관심이 그리 높지않은 실정이다. 본 연구는 양산시 청소년들의 영구치에 나타난 치아침식증의 유병율을 조사하고 설문지를 통하여 그 위험요인을 분석할 목적으로 시도되었다. 양산시에 거주하는 13-15세 중학생 1,371명을 대상으로 단일 검사자가 영구치의 치아침식증 상태를 조사하였다. 치아침식증의 평가기준으로는 Visual Erosion Dental Examination system을 사용하였다. 또한 설문지를 통하여 이들의 식이습관 및 구강위생상태와 치아침식증 간 유의성을 비교ㆍ분석하였다. 치아침식증은 676명(49.3%)에서 관찰되었고, 남성(46.4%)에 비해 여성(53.0%)이 더 높은 유병율을 보였다(p < 0.05). 상악(39.3%)에 비해 하악(43.0%)에서 더 높았으나(p < 0.05), 좌ㆍ우측 간에는 차이가 없었다. 구치에 비해 전치의 유병율 및 치아 당 평균점수가 높았다. 가당 및 무가당우유는 치아침식증에 영향을 미치는 반면(p < 0.05), 다른 음료, 식이섭취방법, 구강위생, 그리고 BMI의 영향은 미미했다(p > 0.05). 본 연구에서 나타난 유병율은 20~30% 내외인 다른 보고들에 비해 높았으며, 남성이 호발한다는 기존의 보고들과 달리여성에서 유병율이 더 높았다. It is a trend that carbonated drink intake among adolescents is increasing, which makes young people more vulnerable to dental erosion. However, in Korea, public knowledge about dental erosion is very insufficient. The aim of this study was to investigate the prevalence of dental erosion and to assess its risk indicators among 13- 15 years old students in Yangsan, Korea. A total of 1,371 adolescents were examined by one calibrated clinician. Dental erosion was assessed by using the Visual Erosion Dental Examination system. Correlation between their dietary habit, oral hygiene and dental erosion was assessed. The data showed that 676 (49.3%) adolescents had dental erosion. The prevalence of dental erosion was significantly higher in females than in males. The prevalence of tooth erosion in mandible is higher than in maxilla. Dental erosion was generalized to develop mostly on anterior teeth, especially lateral incisor, however, the severity score was highest in canines. Following questionnaire analysis, dental erosion was significantly associated with milk and flavored milk. No other associations were detected. The prevalence of dental erosion in this study is higher than those of previous reports. On the contrary to previously reported studies, the prevalence of dental erosion in females is higher than in males.

Influence of physicochemical properties of model compounds on their release from biodegradable polyanhydride devices

Park, Eun-Seok,Maniar, Manoj,Shah, Jaymin C. 성균관대학교 약학연구소 1997 成均藥硏論文集 Vol.9 No.1

A new class of fatty acid dimer-based polyanhydride, polycfatty acid dimer-sebacic acid) (P(FAD-SA)), was reported to have desired physicochemical and mechanical properties for a biodegradable device and believed to undergo pure surface erosion. The objectives of this study were to determine if P(FAD-SA) undergoes pure surface erosion, and to identify the factors governing the release characteristics and mechanism from polyanhydride devices at various pHs. Three model compounds, mannitol (small M_w, highly water soluble), inulin (large M_w, moderately water soluble) and stearic acid (medium M_w, extremely lipophilic) were incorporated at 10% w/w in disk-shaped P(FAD-SA, 50:50 w/w) devices and the release of the compounds studied from pH 1-9. All the three model compounds were released faster at alkaline pH than at acidic pH (pH 9>pH 7.4>pH 1-5), suggesting that the release of model compounds was dependent on the catalyzed erosion of polyanhydride. However, erosion was not the sole release rate controlling mechanism for these model compounds. Highly water soluble mannitorl and inulin were released rapidly at acidic pH, when erosion of polyanhydride is negligible. Mannitol released faster than inulin, which was released faster than lipophilic stearic acid at all pH, suggesting that the hydrophilic/hydrophobic nature of the loaded compound influenced its release significantly. the observed release profiles were significantly higher, and did not match the release profiles predicted from erosion rates of the mannitol and inulin devices, however they were closer for stearic acid devices. Althoug inulin was released rapidly in the initial phase (40-50%), only 60-70% inulin was released over a 6-week period compared to 100% release of mannitol. The large molecular size of inulin may have hindered its diffusion through water-filled pores and channels observed in the devices during release, which may have resulted in the majority of inulin being still trapped in the devices. Although various contributing factors in overall release were identified, a single release kinetic model could not explain the release profiles of all the loaded compounds under the different pH conditions. The complete release profiles could be decribed by first order kinetics, however the initial release profiles of all the model compounds were described very well by zero order kinetics. The release rates of mannitol and inulin were influenced by both the erosion rates and the intrinsic dissolution rates unlike release rates of stearic acid which correlated closely with erosion rates. This may be due to the fact that different release machanisms, such as diffusion, dissolution and erosion all play a significant role in overall release of compound from this newly developed P(FAD-SA) device. However, the contribution of each process to overall release may vary as a function of pH, the nature of the compound and polymer erosion. In conclusion, the results suggest that P(FAD-SA, 50:50 w/w) is undergoing bulk erosion rather than the desired surface erosion. If it did undergo surface erosion, release characteristics would be independent of the physicochemical nature of the incorporated compound and release kinetics would be zero order from disk-shaped devices irrespective of the nature of the loaded compound.

An experimental study on cavitation erosion-corrosion performance of ANSI 1020 and ANSI 4135 steel

Leqin Wang,Ning Qiu,Dieter-Heinz Hellmann,Xiaowen Zhu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.2

Cavitation erosion is quite complex, containing corrosion-erosion interaction effect. High temperature oxidization may be aroused after bubble collapse, accompanied by hot gas contacting with the pump component surface. The analysis of the erosion pits can be an effective way to know the mechanism of cavitation erosion. In present paper, the cavitation erosion resistance of carbon steel (ANSI 1020) and alloy steel (ANSI 4135) were tested in an ultrasonic vibration apparatus. By using energy dispersive X-ray spectroscope and three dimensional laser microscope, the chemical composition around erosion pits and the oxidation film structure were analyzed. By using metallographic microscope and scanning electronic microscope, the metallographic structure of specimens (e.g., carbon steel and alloy steel), the nano structured iron oxide and corresponding influence on specimen’s anti-erosion performance were discussed. Based on the comparison between the different tests performed in distilled water and tap water respectively, results can be obtained that erosion rate of carbon steel and alloy steel varies with the component of water which had close correlation to the oxidation effect. Erosion rate of alloy steel 4135 was much lower in distilled water compared to tap water while the difference of carbon steel 1020 was not that large. The remarkable different responses of these two materials had close relationship with oxidation effect. The oxidation effect transferred the original structure of alloy steel surface which had high anti-erosion capability, into newly generated iron oxide structure, which was preferentially to be attacked. The pumping of slightly corrosive fluids frequently leads to erosion-corrosion damage on impellers, and corrosion can further amplify the erosion process.

Rader Tracer Erosion Analysis of Dongzhiyu District Based on Radar Imagery

( Chengcheng Jiang ),( Wen Fan ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Dongzhiyuan is largest Plateau, which is known as “the first Plateau in the word”. The head-cut erosion companying with serious water erosion and gravity erosion pushes forward the hinterland to continuous shrinkage of Plateau surface. In this paper, we proposed the combination of small baseline subset (SBASInSAR) and Permanent scattering (PS-InSAR) technologiesto the measurement of the deformation time series of erosion. To get the distribution map of trace erosion settlement, 21 ALOS PALSAR of L-Band images from 2007 to 2011 were analysised. The typical erosion areas in this study area were selected by techniques such as ArcGIS and ENVI, and the interpretation of the gully traceable erosion and surface settlement distribution was analyzed. Based on the geological conditions such as rainfall data and soil conditions within the corresponding years of the satellite imagery, the characteristics of erosion and sedimentation are discussed from the origin and development process of traceability erosion.The result shows that the rainfall, soil and human activities are the main factors impacting head-cut erosion. The average subsidence rate is -6.3mm/yr, while the highest subsidence rate of -50.1mm/yr occurring in the subsidence. We summed up the process of head-cut erosion occurrence and put forward the control measures. It can be summarized as plateau surface measures and gully bottom measure. Through the actual investigation, the accuracy of the interpretation analysis is verified, which provides theoretical basis and reference for the prevention and treatment of erosion in the region.

A Study on Efficient Management Strategy for Soil Erosion

황정배,김남찬,임창인,강윤민 한국토양비료학회 2018 한국토양비료학회지 Vol.51 No.4

Soil value was estimated 26 trillion Korean won and recent climate change due to global warming is highly affecting soil erosion. Especially, about 10% of surface soil was annually eroded because of massive construction in Korea. Main purpose of this research was i) to investigate occurrence, mechanism, affecting parameters of soil erosion especially focused on wind erosion and ii) to conduct wind tunnel experiment for evaluating feasibility of dry fog system in stabilizing wind erosion. Result of wind tunnel experiment showed that wind erosion could be reduced about 22-38% after applying dry fog system. Two parameters, soil particle size and spreaded water drop size, are main parameters to affect efficiency of wind erosion stabilization and smaller water drop size is more effective to prevent wind erosion than soil particle size. In terms of wind erosion management, evaluation of soil erosion should be conducted for environmental impact assessment (EIA) when land usage is changed or massive construction was conducted. Since there is no evaluation form of soil erosion in EIA, not only soil erosion but also wind erosion evaluation should be included in the EIA. In addition, transaction of soil and rock open portal recycle system (TOCYCLE) could be utilized to recycle surface soil and consequently, prevent wind erosion and conserve value of soil. Overall, dry fog system is an effective technique for wind erosion preventing system and it could be combined with natural and/or artificial soil conservation system to enhance wind erosion prevention. Furthermore, policy and management system for preventing soil erosion should be thoroughly reviewed to make better soil conservation.

산취급사업장근로자에서 산의 원천별 치아부식증의 분포 및 연관 요인에 관한 조사연구

박승민 ( Seung-min Park ),신명섭 ( Myung-seop Shin ),공미선 ( Mi-sun Kong ),김현덕 ( Hyun-duck Kim ) 대한구강보건학회 2016 大韓口腔保健學會誌 Vol.40 No.4

Objectives: No evidence has been found on various types of dental erosion, except for occupational dental erosion. This study aimed to evaluate the distribution of four types of dental erosion (occupational, dietary, systemic, and gastric) and its associated factors among workers in factories that use acids. Methods: Of 89,034 workers from 4,625 factories that use acids, 716 workers from 38 factories were selected for this cross-sectional epidemiological study by using three-stage stratified cluster sampling. Evaluation for dental erosion was performed by a trained dentist by using Kim`s criteria, and a saliva sample was collected directly from each participant. Data on acid sources and associated factors were collected by using questionnaires. By using a complex sample analysis, the T test and Rao-Scott chisquare test were applied to analyze the distribution of four acid factors and to evaluate the associated factors. Results: The prevalence of overall dental erosion was 37.7% for occupational dental erosion, 23.1% for dietary dental erosion, 3.1% for systemic dental erosion, and 3.2% for gastric dental erosion. The prevalence of severe dental erosion was 10.5% for occupational dental erosion, 7.1% for dietary dental erosion, 1.8% for systemic dental erosion, and 1.7% for gastric dental erosion. The factors associated with dental erosion were age, sex, acid exposure, dental cervical abrasion, and dental attrition. Conclusions: Our data showed that the prevalence of dental erosion was high, moderate, and low in occupational, dietary, and gastric and systemic dental erosions, respectively, among workers exposed to acids. The related factors differed according to the types of dental erosion. Our data suggested that different types of promotion programs for dental erosion should be considered according to acid source.