• 한국물환경학회지
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• 제27권3호
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• pp.257-263
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• 2011

This study analyzes the correlations between non-point sources and runoff to estimate non-point sources for effective management. From the monitoring results, the correlation factors among pollutant mass loading, EMC, total runoff volume and average flow are calculated. And using correlation factors, the most related two constituents are determined. Also the most appropriate regression between two constituents are determined. Pollutant mass loading and total runoff volume has the highest correlation. Also, compound regression is found to be the most appropriate regression. This shows that pollutant mass loading increases as total runoff volume increases. It is not continuous increase but has some pattern.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.644-649
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• 1993

Practical structures are subject not only to tension but also to shear and torsional loading. In this study, the mode 1 and 2 stress intensity factors of specimens were calculated by using elastic finite element mothod. The stress fields at the crack tip subjected to mixed-mode loading were also studied by usingf eleatic finite element method and were compared with theoretical results. The three-point-bending, four-point-bending, and mixed-mode-loading experiment were carried out. And, crack propagation rate da/dN and crack growth direction were examined. Also, the elastic finite element method was applied to calculate the stress intensity factors of branch crack tip and we relate the stress intenity factor range of branch crack tip(the result of FEM) to crack propagation rate(the experimental result). The .DELTA. -da/dN relation corelated with that of mode 1.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1212-1218
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• 2003

A novel loading mechanism of wedge roller type has been developed. This type traction drive has long system life and high efficiency by changing the pre-load on a contact point. And this loading mechanism does not need precision machining. So it has, as opposed to the conventional loading mechanism, an advantage in saving manufacturing cost. In this paper, by analyzing pre-load generating mechanism, spring pre-load and the roller size are defined and the stress on the contact point by pre-load is calculated. On the basis of this analysis, the model of wedge roller type traction drive for the test is made and was carried out its performance test. It can transmit input torque up to 1.5 N m, with high efficiency over 91% up to 98%, with slip rate under 2.5%.

• 대한치과기공학회지
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• 제27권1호
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• pp.105-113
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• 2005

The purpose of this study is to evaluate the effect of loading at three different occlusal surface position of the gold alloy crown on the stress distributions in surrounding bone, utilizing 3-dimensional finite element method. A three dimensional finite element model of an implant with simplified gold alloy crown and supporting bone was developed for this study. A oblique or vertical load of 100 N was applied at the following position at each FE model : 1) center of occlusal surface, 2) a point on the buccal side away from center of occlusal surface (COS) by 2.8mm, 3) a point on the lingual side away from COS by 2.8mm. In the results, Minimum von Mises stresses under vertical load or oblique load of 100N were about 6MPa at the center of occlusal surface and about 40MPa at the point on the buccal side, respectively. From the results we could come to the conclusion that occlusive loading position could be an important factor for establishment of structural safety of supporting bone.

• Geomechanics and Engineering
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• 제14권5호
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• pp.459-466
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• 2018

By conducting uniaxial loading cycle tests on the coal rock with outburst proneness, the dilatation characteristics at different loading rates were investigated. Under uniaxial loading and unloading, the lateral deformation of coal rock increased obviously before failure, leading to coal dilatation. Moreover, the post-unloading recovery of the lateral deformation was rather small, suggesting the onset of an accelerated failure. As the loading rate increased further, the ratio of the stress at the dilatation critical point to peak-intensity increased gradually, and the pre-peak volumetric deformation decreased with more severe post-peak damage. Based on the laboratory test results, the lateral deformation of the coals at different depths in the #1302 isolated coal pillars, Yangcheng Coal Mine, was monitored using wall rock displacement meter. The field monitoring result indicates that the coal lateral displacement went through various distinct stages: the lateral displacement of the coals at the depth of 2-6 m went through an "initial increase-stabilize-step up-plateau" series. When the coal wall of the working face was 24-18 m away from the measuring point, the coals in this region entered the accelerated failure stage; as the working face continued advancing, the lateral displacement of the coals at the depth over 6 m increased steadily, i.e., the coals in this region were in the stable failure stage.

• Journal of Ecology and Environment
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• 제40권1호
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• pp.66-74
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• 2016

Background: When developing water quality improvement strategies for eutrophic lakes, questions may arise about the relative importance of point sources and nonpoint sources of phosphorus. For example, there is some skepticism regarding the effectiveness of partial reductions in phosphorus loading; because phosphorus concentrations are too high in hypertrophic lakes, in-lake phosphorus concentrations might still remain within typical range for eutrophic lakes even after the reduction of phosphorus loading. For this study, water quality and the phytoplankton and zooplankton communities were monitored in a hypertrophic reservoir (Lake Wangsong) before and after the reduction of phosphorus loading from a point source (a sewage treatment plant) by the installation of a chemical phosphorus-removal process. Results: Before phosphorus removal, Lake Wangsong was classified as hypertrophic with a median phosphorus concentration of $0.232mg\;L^{-1}$ and a median chlorophyll-a concentration of $112mg\;L^{-1}$. The dominant phytoplankton were filamentous cyanobacteria for the most of the ice-free season. Following the installation of the advanced treatment process, phosphorus concentrations were reduced to $81mg\;L^{-1}$, and the N/P atomic ratio increased from 42 to 102. Chlorophyll-a concentrations decreased to $42{\mu}g\;L^{-1}$, and the duration of cyanobacterial dominance was confined to the summer season. Cyanobacteria in spring and autumn were replaced by diatoms and cryptomonads. Filamentous cyanobacteria in summer were replaced by colony-forming unicellular Microcystis spp. It was remarkable that zooplankton biomass increased despite the decrease in phytoplankton biomass, and especially cladoceran zooplankton which increased drastically. These responses to the reduction of point source P loading to Lake Wangsong imply that reducing the point source P loading can have a big impact even when nonpoint sources account for a large fraction of the total annual phosphorus loading. Conclusions: Our results also show that the phytoplankton community can shift to decreased cyanobacterial dominance and the zooplankton community can shift to higher cladoceran dominance, even when phosphorus concentrations remain within the typical range for eutrophic lakes following the reduction of phosphorus loading.

• Structural Engineering and Mechanics
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• 제11권5호
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• pp.565-574
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• 2001

Experimental investigation into the behaviour of half-scale brick masonry panels were conducted under cyclic loading normal to the bed joint and parallel to the bed joint. For each cycle, full reloading was performed with the cycle peaks coinciding approximately with the envelope curve. Unloading, however, was carried out fully to zero stress level and partially to two different stress levels of 25 percent and 50 percent of peak stress. Stability point limit exhibits a unique stress-strain curve for full unloading but it could not be established for partial unloading. Common point limit was established for all unloading-reloading patterns considered, but its location depends on the stress level at which unloading is carried to. Common point curves were found to follow an exponential formula, while residual strains versus envelope strains can be expressed by a polynomial function of a single term. The relation between residual strain and envelope strain can be used to determine the stress level at which deterioration due to cyclic loading began.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권1호
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• pp.75-86
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• 2023

The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generates various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

• 대한치과교정학회지
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• 제28권4호
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• pp.659-668
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• 1998

본 연구는 브라켓 간접부착술식시 레진 베이스의 두께에 따른 전단결합강도와 파절양상을 비교함으로써 레진 베이스 두께 증가시 전단결합강도의 저하여부를 평가하기 위하여 시행되었다. 소의 하악 절치를 포매하여 만든 레진블럭에 micromanipulator를 사용하여 치면과 브라켓 기저면 사이의 광중합형 접착제가 0.0, 0.5, 1.0, 1.5, 2.0 mm두께가 되도록 각각 브라켓을 부착한 다음 만능물성시험기를 이용하여 치면으로부터 하중 위치까지의 거리를 일정하게 유지하면서 레진 베이스의 두께를 증가시킨 경우와 레진 베이스 두께의 증가와 함께 치면으로부터 하중 위치까지의 거리를 증가시킨 경우로 나누어 전단결합강도를 측정하고 파절양상을 관찰하여 다음과 같은 결과를 얻었다. 1. 치면으로부터 하중 위치까지의 거리를 일정하게 유지한 경우 레진 베이스 두께의 증가와 함께 브라켓 기저부로부터 하중 위치까지의 거리가 감소함에 따라 전단결합강도가 유의하게 증가하였다. 2. 레진 베이스 두께의 증가와 함께 치면으로부터 하중 위치까지의 거리를 증가시킨 경우 전단결합강도가 감소하는 것으로 나타났으나 그 유의차는 미미하였다. 3. 접착제 잔류지수를 이용하여 레진 베이스의 두께에 따른 파절양상을 비교 관찰한 결과 유의한 차이를 보이지 않았다. 이상의 실험결과를 볼 때 브라켓 부착시 레진 베이스의 두께에 따른 전단결합강도는 브라켓 기저부로부터 하중 위치까지의 거리가 증가함에 따라 감소하는 반면 레진 베이스 두께의 영향은 크게 받지 않는 것으로 나타났다.

• 한국물환경학회지
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• 제23권6호
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• pp.951-960
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• 2007

Window interface to Hydrological Simulation Program-FORTRAN (WinHSPF) developed by the United States Environmental Protection Agency (EPA) was applied to the upstream of Nam-Han river watershed to examine its applicability for loading estimates in watershed scale and to evaluate non-point source control scenarios using BMPRAC in WinHSPF. The WinHSPF model was calibrated and verified for water flow using Ministry of Construction and Transportation (MOCT, 3 stations, 2003~2005) and water qualities using Ministry of Environment (MOE, 5 station, 2000~2006). Water flow and water quality simulation results were also satisfactory over the total simulation period. But outliers were occurred in the time series data of TN and TP at some regions and periods. Therefore, it required more profit calibration process for more various parameters. As a result, all the study was performed within the expectation considering the complexity of the watershed, pollutant sources and land uses intermixed in the watershed. The estimated pollutant load for annual average about $BOD_5$, T-N and T-P respectively. Nonpoint source loading had a great portion of total pollutant loading, about 86.5~95.2%. In WinHSPF, BMPRAC was applied to evaluate non-point source control scenarios (constructed wetland, wet detention ponds and infiltration basins). All the scenarios showed efficiency of non-point source removal. Overall, the HSPF model is adequate for simulating watersheds characteristics, and its application is recommended for watershed management and evaluation of best management practices.