• Ecology and Resilient Infrastructure
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• v.8 no.1
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• pp.54-63
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• 2021

This study aimed to investigate changes in benthic macroinvertebrate communities caused by erosion control dams using data obtained from three erosion control dams in Wonju, Gangwon Province, before and after the rainy season. Surveys were conducted four times from March to September 2019, and survey points were continuously selected during the installation of closed-type and open-type dams. A total of eight points from the upstream and downstream regions of each dam type were selected. The flow velocity of both the closed and open types increased, but the closed type exhibited a relatively higher flow velocity than the open type. Benthic macroinvertebrate species and individuals mostly decreased after the rainy season. A relatively large number of species and individuals were found upstream of the closed-type dam. An analysis of the ephemeroptera-plecoptera-trichoptera groups showed relatively reduced ephemeroptera in the closed-type dam and reduced trichoptera in the open-type dam. The periods before and after the rainy season could be divided based on the results of a similarity analysis. The open type showed relatively minimal changes before and after the rainy season.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.6
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• pp.593-601
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• 2020

Two-dimensional laboratory experiments were conducted in a wave flume to investigate the wave transmission phenomena of impermeable-type submerged structures armored by concrete blocks. Different experimental conditions were included by considering relative crest depth, relative freeboard, relative crest width, wave steepness, and so on. An empirical formula was proposed to predict the wave transmission coefficients over various specifications and structural designs of the impermeable submerged structure from the experimental results. The proposed formula successfully predicted the wave transmission coefficients. Therefore, in this study, the proposed empirical formula of the wave transmission over an impermeable submerged structure was improved from the existing formula.

• Korean Journal of Environment and Ecology
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• v.34 no.2
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• pp.121-129
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• 2020

This study investigated the change of benthic macroinvertebrates community due to erosion control dams installed in Wonju, Gangwon by comparing the data before and after a rainy season. It selected a closed-type erosion control dam (boulder stone), an open-type erosion control dam (buttress), and a control area and surveyed two upstream points and two downstream points four times between March and September 2019. The flow velocity mostly increased in the closed-type, open-type, and control areas but decreased in St. 3 after the rainy season. The number of benthic macroinvertebrates species and their populations mostly decreased after the rainy season, and the rate of decrease in the populations in the open-type and control areas were more similar than the closed-type area. Species and populations of the EPT groups mostly decreased after the rainy season. A result of the similarity analysis showed that the closed-type and open-type areas were separated by 38.4% with the control area before the rainy season, but the open-type and control areas were separated by 51.3% with the closed-type area after the rainy season. A result of the principal components analysis (PCA) based on axis 1 showed that the closed-type area had a positive value before and after the rainy season, and the open-type and control areas had a negative value before and after the rainy season. The open-type area was more correlated with the control area than the close type. The analysis of the EPT groups showed the distribution of Ephemeroptera in the closed-type area and Trichoptera in the open-type and control areas. The result of this study shows that the installation of erosion control dam can cause changes in benthic macroinvertebrates community and that the open-type area had a smaller difference community difference from the control area after the rainy season than the closed-type area.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.180-180
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• 2016

최근 기후변화로 인한 국지성 집중호우의 영향으로 재해의 다양화, 대형화 하고 있다. 그 중, 산지하천에서 발생하는 재해로는 토석류 재해가 있다. 일반적으로 토석류 재해는 발생시기, 발생 위치, 발생규모 등을 예측하기 어렵다는 특징을 가지고 있기 때문에 토석류 재해의 피해를 저감시키기 위해서 국내에서는 사방사업을 주로 실시하고 있다. 사방사업에 이용되는 사방댐은 투과형 사방댐과 불투과형 사방댐으로 크게 분류된다. 불투과형 사방댐은 전체적인 토석류의 양을 줄여주는 역할을 하며, 투과형 사방댐은 바위, 토사 등을 물과 분리하여 토석류의 위력을 감소시키는 역할을 한다. 이러한 투과형 사방댐과 불투과형 사방댐의 장점을 이용하여 적절히 조합한다면 토석류 유출저감 효과를 극대화 시킬 수 있을 것으로 보인다. 본 연구에서는 조합형 사방댐의 저감효과를 검증하기 위해 다기능을 사방댐을 설계하였다. 설계한 사방댐은 중력식 콘크리트 사방댐, 버트리스, 브레이커의 3가지 파트로 구성 하였다. 실험에 활용하기 위한 모형을 각각 분리하여 제작하고, 각각의 조합에 따라 가장 높은 저감효과를 내는 조합을 찾기 위해 토석류 모형실험을 실시하였다.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.191-205
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• 2017

We use small-scale modelling to estimate the impact ofrce of debris flows on erosion control dams (ECD) and ring nets. The results indicate that the viscoelastic debris flows produced impact forces of 4.14, 3.66, 1.66 kN from the bottom to the top of the ECD. Ring net tests produced a similar trend with generally smaller impact forces (2.28, 1.95, and 1.49 kN). Numerical analysis showed that the weight of the ECD (e.g., concrete retaining walls) provided resistance against the debris flow, whereas deformation of the ring net by elastic-elongation and aggregate penetration reduced the impact force by up to 45% compared with that of the ECD.

• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.15-22
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• 2013

5 each permeable and impermeable debris dams were selected to analyze the characteristics of dredging and sedimentation according to facility type in Inje, Gangwon. Field tests for the ground water table and sedimentation characteristics of the selected dams were performed. Furthermore, data of the dredging amount, storage capacity, and drainage area were analyzed for the 51 more debris control facilities. From the results of field tests, it was found that the storage capacity of impermeable debris dam could be not enough when the large debris flow is produced since sediments are accumulated even if large debris flow was not occurred. Drainage can be a problem since the ground water table of impermeable debris dam was reached to the surface of ground. However, it was found that the ground saturation should not occur at heavy rain since ground water table of permeable debris dam was located in lower part of buttress. Furthermore, from the analysis results of relation among the dredging amount, basin area, and capacity of debris control facility, it was found that size of debris control facility was not reflected by the basin area. Effective planning and construction should be accomplished for the future since the real sedimentation amount was not significant even though large debris dams were constructed.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.1-12
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• 2018

This study was conducted to analyze the openness of erosion control dams situated near mountain stream. The ecological functions of erosion control dams analyzed by such openness for adequately protect and manage the diversity of species and to prevent disasters. The obtained results were as follows. When structurally modifying or changing non-permeable, gravity type dams with a passing rate of less than 1% into open-type dams, the passing rate increased by about 77 times more from 0.72% to 55.8%. Except for closed, gravity type erosion control dams that are constructed with a special purpose such as creating sand deposits and reservoirs, there is a need to construct and improve the dams into permeable type dams that can relatively satisfactorily perform various functions such as carrying soil and sand to the downstream region and create a ecological corridor upstream and downstream for fish and amphibians. The openness based on the blocking height of the erosion control dam varies depending upon the height of the base part and the depth of the substructural part. It must be designed based on the on-site conditions and the purpose of the construction. The functional types of erosion control dams based on the open form of the cross-section as follows: the fish traffic type, flood control type, reservoir type for forest fire control), non-permeability type for soil and rock blocking, net type for blocking the rock flow and the particle screen type.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.3
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• pp.423-429
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• 2002

Recently, the clinical uses of flowable composite resins have increased because of fast, convenient and excellent accessibility, but little has been reported about physical properties of flowable resins. The purpose of this study was to measure and compare the physical properties(compressive strength, relative flowability, relative radiopacity) of 4 contemporary flowable composite resins(Filtek flow, Tetric Flow, Revolution Palfique Estelite LV high flow). The results were as follows; 1. There were no significant differences between 4 flowable composite resins in compressive strength, but all were lower than that of traditional hybrid composite resin(p<0.001). 2. The relative flowability were increased in order of Palfique Estelite LV high flow, Revolution, Filtek flow, Tetric Flow and sealant(p<0.001), but there were no significant differences between Filtek flow and Tetric Flow. 3. There were significant differences between flowable composite resins in relative radiopacity and they showed similar or higher radiopacity than dentin(p<0.001), especially Tetric Flow and Filtek Flow showed higher radiopacity than enamel(p<0.001). This results suggested that the stress of application area have to be considered since flowable composite resins have lower compressive strength than hybrid composite, and the differences of flowability between these flowable composite resins can be considered when they are selected. All tested flowable composite resins showed optimal radiopacity to ISO's recommend.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.97-104
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• 2014

This study was aimed to compare the radiopacity of four kinds of currently available resin based implant cements using digital radiography. Materials and Methods: Four resin-based implant cements((Estemp $Implant^{TM}$ (Spident, Incheon, Korea), $Premier^{(R)}$Implant (Premier, Pennsylvania, USA), $Cem-Implant^{TM}$ (B.J.M lab, Or-yehuda, Israel), $InterCem^{TM}$ (SCI-PHARM, California, USA)) and control group (Elite Cement $100^{TM}$ (GC, Tokyo, Japan) ) were mixed and cured according to the manufacturer's instructions on the custom made split-type metal mold. A total of 150 specimens of each cement were prepared and each specimen (purity over 99%) was placed side-by-side with an aluminum step wedge for image taking with Intraoral X-ray unit (Esx, Vatech, Korea) and digital X-ray sensor (EzSensor, Vatech, Korea). For the evaluation of aluminum wedge equivalent thickness (mm Al), ImageJ 1.47 m (Wayne Rasband, National Institutes of Health, USA) and Color inspector 3D ver 2.0 (Interaktive Visualisierung von Farbraumen, Berlin, Germany) programs were used. Result: Among the 5 cements, Elite cement $100^{TM}$ (control group) showed the highest radio-opacity in all thickness. In the experimental group, $InterCem^{TM}$ had the highest radio-opacity followed by $Premier^{(R)}$ Implant $Cement^{TM}$, $Cem-Implant^{TM}$ and Estemp $Implant^{TM}$. In addition, $InterCem^{TM}$ showed radio-opacity that met the ISO No. 4049 standard in all the tested specimen thickness. Cem-Implant on 0.5 mm thickness showed radiopacity that met the ISO No. 4049 standard. Conclusion: Among the implant resin-based cements tested in the study, $Premier^{(R)}$ Implant Cement and Estemp $Implant^{TM}$ did not show appropriate radio-opacity. Only $InterCem^{TM}$ and $Cem-Implant^{TM}$ 0.5 mm specimen had the proper radiopacity and met the experiment standard.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.80-87
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• 2017

Purpose: The aim of this study was to assess the physical properties of a novel resin-based endodontic sealer, Any-Seal, in comparison with AH Plus Jet. Materials and Methods: Flow, radiopacity and compressive strength were examined according to ISO 6876/2001. For flow test, 0.05 mL of sealer was placed between glass plate and 100 g weight were applied. Ten minutes after mixing the sealers, the load was removed and the diameters of the compressed sealer discs were measured. For radiopacity, 10 mm diameter and 1 mm thickness sample were fabricated and took radiograph with an aluminum step-wedge and analyzed using imaging program. For compressive strength test, $4mm{\times}6mm$ cylindrical specimen was fabricated and tested after 24 hours and 1 week using Universal testing machine. Results: Both tested sealers were consistent with ISO 6876/2001 in the flow and radiopacity test. The flow values of both sealers were not significantly different (P > 0.05). AH Plus Jet had significantly higher radiopacity (P < 0.05). AH Plus Jet showed higher compressive strength at both time intervals (P < 0.05). Conclusion: Any-Seal showed low compressive strength until after 1 week, so its physical and biological aspect should be evaluated more before clinical use.