• Title/Summary/Keyword: Field engineering

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Stable Channel Analysis and Design for the Abandoned Channel Restoration Site of Cheongmi Stream using Regime Theory (평형하상 이론을 이용한 청미천 구하도 복원 대상구간의 안정하도 평가 및 설계)

  • Ji, Un;Julien, Pierre Y.;Kang, Joon Gu;Yeo, Hong Koo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.3B
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    • pp.305-313
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    • 2010
  • River restoration or rehabilitation should be conducted in a way to maximize the channel stability with natural river configuration close to the equilibrium condition considering divers aspects of fluvial hydraulics, erosion and sedimentation, fluvial geomorphology, and ecological environment and to minimize the maintenance work. Therefore, the channel stability evaluation for present condition based on the equilibrium channel concept should be preceded for the river restoration project. Methods for equilibrium channel theory have generally been developed following either analytical regime theory or empirical regime theory. The main purpose of this paper is to evaluate the stability of present channel condition for the section of abandoned channel restoration in Cheongmi Stream using the Stable channel Analytical Model (SAM) and equilibrium hydraulic geometry equations. The results of analytical and empirical regime theories should provide fundamental and essential information to design the stable channel geometry. As a calculation result of Copeland's method for the study reach, the equilibrium channel has a narrower channel width, deeper water depth, and more gentle slope than the present channel geometry. As results of equilibrium hydraulic geometry equations, predicted equilibrium widths are less than the channel width in the field. It is represented that the current bed slope must be gentle to reach the equilibrium condition according to the results of Julien and Wargadalam method.

Temperature Effect on the Growth and Odorous Material (2-MIB) Production of Pseudanabaena redekei (온도가 남조류 Pseudanabaena redekei의 성장과 냄새물질(2-MIB) 생산에 미치는 영향)

  • Jaehyun Kim;Keonhee Kim;Chaehong Park;Hyunjin Kim;Soon-Jin Hwang
    • Korean Journal of Ecology and Environment
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    • v.56 no.2
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    • pp.151-160
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    • 2023
  • Cyanobacteria Pseudanabaena strains are known to produce 2-MIB(odorous material) in freshwater systems, thereby causing problems in water use. However, their physiological responses to environmental factors in relation with 2-MIB production is not well explored. This study was conducted to evaluate the effect of temperature on the growth and 2-MIB production of Pseudanabaena redekei. The experimental cyanobacteria strains were separated from the Uiam Reservoir (North Han River) and cultured in the BG-11 medium. Temperature was set to 10, 15, 20, 25, and 30℃ for the experiment, in the reflection of the seasonal water temperature variation in situ. For each temperature treatment, cyanobacterial biomass(Chl-a) and 2-MIB concentration (intra-cellular and extra-cellular fractions) were measured every 2 days for 18 days. Both maximal growth and total 2-MIB production of P. redekei appeared at 30℃. While intra-cellular 2-MIB contents were similar (26~29 ng L-1) regardless of treated temperatures, extra-cellular 2-MIB concentration was higher only in high temperature conditions (25~30℃), indicating that the extents of 2-MIB biosynthesis and release by P. redekei vary with temperature. The 2-MIB productivity of P. redekei was much higher in low-temperature conditions (10~15℃) than high temperature conditions (25~30℃). This study demonstrated that temperature was a critical factor contributing to 2-MIB biosynthesis and its release in cell growth (r=0.605, p<0.01). These results are important to understand the dynamics of 2-MIB in the field and thereby provide basic information for managing odorous material in drinking water resources.

Matching of Topic Words and Non-Sympathetic Types on YouTube Videos for Predicting Video Preference (영상 선호도 예측을 위한 유튜브 영상에 대한 토픽어와 비공감 유형 매칭)

  • Jung, Jimin;Kim, Seungjin;Lee, Dongyun;Kim, Gyotae
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2021.10a
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    • pp.189-192
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    • 2021
  • YouTube, the world's largest video sharing platform, is loved by many users in that it provides numerous videos and makes it easy to get helpful information. However, the ratio of like/hate for each video varies according to the subject or upload time, even though they are in the same channel; thus, previous studies try to understand the reason by inspecting some numerical statistics such as the ratio and view count. They can help know how each video is preferred, but there is an explicit limitation to identifying the cause of such preference. Therefore, this study aims to determine the reason that affects the preference through matching between topic words extracted from comments in each video and non-sympathetic types defined in advance. Among the top 10 channels in the field of 'pets' and 'cooking', where outliers occur a lot, the top 10 videos (the threshold of pet: 4.000, the threshold of cooking: 0.723) with the highest ratio were selected. 11,110 comments collected totally, and topics were extracted and matched with non-sympathetic types. The experimental results confirmed that it is possible to predict whether the rate of like/hate would be high or which non-sympathetic type would be by analyzing the comments.

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Comparison of Carbon Dioxide Emission Concentration according to the Age of Agricultural Heating Machine (농업용 난방기의 사용 연식에 따른 이산화탄소 배출농도 비교)

  • Na-Eun Kim;Dae-Hyun Kim;Yean-Jung Kim;Hyeon-Tae Kim
    • Journal of Bio-Environment Control
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    • v.32 no.3
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    • pp.190-196
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    • 2023
  • This study was carried out to collect gas emitted from agricultural heaters using kerosene and to identify the emission concentration of carbon dioxide according to the age of agricultural heating machine. As a result of the linear regression analysis, the carbon dioxide emissions according to the year of agricultural heating machine are R2 = 0.84, which follows y = 26.99x+721.98. Distributed analysis was classified into three groups according to the age of agricultural heating machine. As a result of the distributed analysis, it was 2.196×10-13, which was smaller than the 0.05 probability set for the analysis, which means that there is a difference in at least one group. As a result, the age of the agriculture machine was divided into three groups and the difference between groups was tested. A statistical analysis result was derived that there was a difference in the emission concentration of carbon dioxide according to the age of agricultural heating machine. It is thought that it can be used to investigate greenhouse gas emissions by investigating the amount of carbon dioxide generated by agricultural heaters in the agricultural field of Korea.

Revision of Repair Materials Performance Requirement for Concrete Structures (콘크리트 구조물 단면복구공사 보수재료 품질기준개선)

  • Lee, Il Keun;Kim, Ki Hwan;Kim, Hong Sam;Yun, Sung Hwan;Kim, Woo Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.1
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    • pp.9-20
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    • 2023
  • For highway concrete structures, the deterioration of the structure is accelerated due to the increase in the use of deicing materials, and sectional repair work is being frequently carried out to restore performance. However, after the repair work, re-damage such as cracks, delamination, and poor bond performance is exhibited in the repaired sectional area. In this study, overseas repair material requirements were first analyzed, and present domestic requirements were improved repair material performance through field surveys of common concrete structures, laboratory experiments, and test construction on a disused concrete bridge. In addition, performancebased quality requirements were presented so that all materials that meet the required performance can be applied, and different test methods for each material were unified into concrete test methods for consistent test results analysis. The considered performance requirements were compression strength, bending strength, and bond strength for structural properties, and length change rate, crack resistance, thermal expansion coefficient, and elasticity coefficient were for dimensional behavior. For resistance to chloride penetration resistance and freeze-thaw resistance were presented as durability. The proposed requirements for concrete repair materials are expected to contribute to the improvement of the quality of concrete sectional repair work in Korea.

GIS-based Debris Flow Risk Assessment (GIS 기반 토석류 위험도 평가)

  • Lee, Hanna;Kim, Gihong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.1
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    • pp.139-147
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    • 2023
  • As heavy precipitation rates have increased due to climate change, the risk of landslides has also become greater. Studies in the field of disaster risk assessment predominantly focus on evaluating intrinsic importance represented by the use or role of facilities. This work, however, focused on evaluating risks according to the external conditions of facilities, which were presented via debris flow simulation. A random walk model (RWM) was partially improved and used for the debris flow simulation. The existing RWM algorithm contained the problem of the simulation results being overly concentrated on the maximum slope line. To improve the model, the center cell height was adjusted and the inertia application method was modified. Facility information was collected from a digital topographic map layer. The risk level of each object was evaluated by combining the simulation result and the digital topographic map layer. A risk assessment technique suitable for the polygon and polyline layers was applied, respectively. Finally, by combining the evaluated risk with the attribute table of the layer, a system was prepared that could create a list of objects expected to be damaged, derive various statistics, and express the risk of each facility on a map. In short, we used an easy-to-understand simulation algorithm and proposed a technique to express detailed risk information on a map. This work will aid in the user-friendly development of a debris flow risk assessment system.

A Study on Reinforcement Method of Concrete Block for Direct Fixation Tracks on Serviced Light Rail Transit (공용중인 경전철 직결 궤도 콘크리트 도상블록의 보강 방안 연구)

  • Jung-Youl Choi;You-Song Kang;Dae-Hee Ahn;Jae-Min Han;Jee-Seung Chung
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.3
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    • pp.633-640
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    • 2023
  • In this study, numerical analysis was performed based on field investigation to derive an appropriate reinforcement method by analyzing the displacement behavior characteristics of concrete blocks generated in the direct fixation track on the bridges of the serviced light rail transit. The track of this study was a direct fixation track on a sharp curved track, and the problem of movement of the concrete blocks installed on the bridge deck in the longitudinal and lateral directions occurred. In this study, based on the finite element model using 3D solid elements, the behavior of the direct fixation track that could be occurred under operating load conditions was analyzed. In addition, the reinforcement effect of various reinforcement methods was analyzed. As a result of analyzing the lateral displacement before and after reinforcement, it was analyzed that the maximum lateral displacement after reinforcement under the extreme lateral wheel loads significantly decreased to about 3% (about 0.1mm) compared to before reinforcement. In addition, as a result of examining the generated stress of the filling mortar, bridge decks, and reinforcing bar, it was analyzed that all of them secured a sufficient safety factor of 2.6 or higher, and the optimal conditions for the reinforcement method were derived. Therefore, it is judged that the number of anchoring reinforcements and symmetrical anchor placement reviewed in this study will be effective in controlling the occurrence of lateral displacement of concrete blocks and securing the structural integrity of bridges and concrete blocks.

Evaluation of the Nonlinearity Parameter in Unbound Material for Asphalt Concrete Pavement using Field-NDT Equipment (현장 도로평가장비를 이용한 입상재료층의 비선형 재료상수 추정에 관한 연구)

  • Seo, Joo Won;Choi, Jun Seong;Kim, Soo Il
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.2D
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    • pp.227-234
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    • 2008
  • This study examines which models are more suitable for representing mechanical property of unbound materials to analyze behavior of asphalt pavement structure. Results from FWD (Falling Weight Deflectometer) test were used to apply to nonlinear elastic model. The new method which can deduct material constants of nonlinear elastic model is suggested from FWD test data rather than laboratory resilient modulus ($M_R$) test. It is confirmed that the material constants are within the common range in subbase. Test output from FWD and MDD (Multi-Depth Deflectometer) was used to verify reliability of the model. From the results of verification, this study shows that a non-linear elastic model agrees to MDD test data more than a linear elastic model does.

Risk of Flood Damage Potential and Design Frequency (홍수피해발생 잠재위험도와 기왕최대강수량을 이용한 설계빈도의 연계)

  • Park, Seok Geun;Lee, Keon Haeng;Kyung, Min Soo;Kim, Hung Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5B
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    • pp.489-499
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    • 2006
  • The Potential Flood Damage (PFD) is widely used for representing the degree of potential of flood damage. However, this cannot be related with the design frequency of river basin and so we have difficulty in the use of water resources field. Therefore, in this study, the concept of Potential Risk for Flood Damage Occurrence (PRFD) was introduced and estimated, which can be related to the design frequency. The PRFD has three important elements of hazard, exposure, and vulnerability. The hazard means a probability of occurrence of flood event, the exposure represents the degree that the property is exposed in the flood hazard, and the vulnerability represents the degree of weakness of the measures for flood prevention. Those elements were devided into some sub-elements. The hazard is explained by the frequency based rainfall, the exposure has two sub-elements which are population density and official land price, and the vulnerability has two sub-elements which are undevelopedness index and ability of flood defence. Each sub-elements are estimated and the estimated values are rearranged in the range of 0 to 100. The Analytic Hierarchy Process (AHP) is also applied to determine weighting coefficients in the equation of PRFD. The PRFD for the Anyang river basin and the design frequency are estimated by using the maximum rainfall. The existing design frequency for Anyang river basin is in the range of 50 to 200. And the design frequency estimation result of PRFD of this study is in the range of 110 to 130. Therefore, the developed method for the estimation of PRFD and the design frequency for the administrative districts are used and the method for the watershed and the river channel are to be applied in the future study.

Numerical Simulation of Depth-Averaged Flow with a CDG Finite Element Method (CDG 유한요소법을 이용한 수심적분 흐름의 수치모의)

  • Kim, Tae Beom;Choi, Sung-Uk;Min, Kyung Duck
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5B
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    • pp.447-457
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    • 2006
  • This paper presents a numerical model for the simulations of 2D depth-averaged flows. The shallow water equations are solved numerically by the Characteristic Dissipative Galerkin (CDG) finite element method. For validation, the developed model is applied to the hydraulic jump. The computed results are compared with the analytical solution, revealing good agreement. In addition, flow in a contracting channel showing standing waves is simulated. The calculated water surface profile appears to be qualitatively consistent with the observed data. The foregoing results indicate that the model is capable of simulating the abrupt change in flow field. Next, the model is applied to the flow in a $180^{\circ}$ curved channel. The simulated results show that the velocity near the inner bank is faster than that near the outer bank and the water depth near the inner bank is shallower than that near the outer bank. However, the simulated results show that the velocity distribution across the channel is almost uniform in the bend except the reach close to the end of the bend. This is due to the limitation of the governing equations in which the transverse convection of momentum by the secondary flows along a channel bend is not taken into account.