• Korean Journal of Environment and Ecology
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• v.29 no.2
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• pp.228-235
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• 2015

Stream ecosystems are closely related to many human activities. Therefore, streams are affected by anthropogenic disturbances such as riverine development and gravel-mining as well as deterioration of water quality. The goal of this study was to elucidate the recolonization process of the macroinvertebrate community after a small-scale anthropogenic disturbance. Field studies were conducted at three sites in a natural stream. The number of recolonizing species tended to increase slightly over time, exceeding the total species number of the control. Ephemeroptera contributed the most to shaping the recolonizing pattern of the entire community. From the result of changes in dominant species, the early recolonizers of each site were the species that showed more frequent occurrence particulary at each sites. But the late recolonizers are Chironomidae at all the sites commonly. This result implies that the actual differences exist among the recolonizing trends of each benthic macroinvertebrate taxon. Collector-gatherers and scrapers comprised about 70% of the recolonizing species. These results indicate that the recolonizing process of an aquatic community after an artificial disturbance depends on the environmental conditions(particularly substratum composition or organic pollution) of the habitat.

• Geomechanics and Engineering
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• v.14 no.6
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• pp.589-600
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• 2018

For foundations in permafrost regions, the displacement characteristics are uncertain because of the randomness of temperature characteristics and mechanical parameters, which make the structural system have an unexpected deviation and unpredictability. It will affect the safety of design and construction. In this paper, we consider the randomness of temperature characteristics and mechanical parameters. A stochastic analysis model for the uncertain displacement characteristic of foundations is presented, and the stochastic coupling program is compiled by Matrix Laboratory (MATLAB) software. The stochastic displacement fields of an embankment in a permafrost region are obtained and analyzed by Neumann stochastic finite element method (NSFEM). The results provide a new way to predict the deformation characteristics of foundations in permafrost regions, and it shows that the stochastic temperature has a different influence on the stochastic lateral displacement and vertical displacement. Construction disturbance and climate warming lead to three different stages for the mean settlement of characteristic points. For the stochastic settlement characteristic, the standard deviation increases with time, which imply that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the stochastic deformation fields of embankments and provide a theoretical basis for engineering reliability analysis and design in permafrost regions.

• Geomechanics and Engineering
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• v.29 no.6
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• pp.697-706
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• 2022

In order to explore the stable anchoring conditions of coal side under the mining disturbance of soft section coal pillar in Wangcun Coal Mine of Chenghe Mining Area, the distribution model of the anchoring support pressure at the coal pillar side was established, using the strain-softening characteristics of the coal to study the distribution law of anchoring coal side support pressure. The analytical solution for the reinforcement anchorage stress in the coal pillar side was derived with the inelastic state mechanical model. The results show that the deformation angle of the roadway side and roof increases with the roof subsidence due to the mining influence at the adjacent working face, the plastic deformation zone extends to the depth of the coal side, and the increase of anchorage stress can effectively control the roof subsidence and further deterioration of plastic zone. The roadway height and the peak support pressure have a certain influence on the anchorage stress, the required anchorage stress of the coal side rises with the roadway height and the peak support pressure. The required anchorage stress of the coal pillar side decreases as the cohesion between the coal seam and the roof and floor and the anchor length increases. Then, applied the research result to Wangcun coal mine in Chenghe mining area, the design of anchor cable reinforcement support was proposed for the section of coal pillars side that has been anchored and deformed, which achieved great results and effectively controlled the convergence and deformation of the side, providing a safety guarantee for the roadway excavation and mining.

• Geophysics and Geophysical Exploration
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• v.6 no.1
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• pp.28-34
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• 2003

A problem of ground subsidence has been a focus of our research over the past 3 years. The purpose of this study is to investigate the disturbed stratigraphic structure by mining and to separate the possible ground subsidence area using shallow seismic reflection survey and processing. To overcome the problems such as the distortion and attenuation of seismic signal caused by ground disturbance and to acquire the high frequency data, an array with short spacing (0.3m) for both the shot and receivers, yielding near-offset (<30m) and CMP spacing of 0.15m was implemented. Data were acquired along the survey line with length of about 43m by fixed receiver array. By considering statics caused by the ground disturbance and offset distribution of data, careful processing steps such as muting and residual statics correction were applied for successful shallow reflection imaging. By correlating the ground subsidence data and stack section, possible subsidence zone could be interpreted quantitatively.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.195-215
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• 2017

This paper proposes gob-side entry retaining by roof break and filling in thick-layer soft rock conditions based on the thick-layer soft rock roof strata migration law and the demand for non-pillar gob-side entry retaining projects. The functional expressions of main roof subsidence are derived for three break roof direction conditions: lateral deflection toward the roadway, lateral deflection toward the gob and vertically to the roof. These are derived according to the load-bearing boundary conditions of the main roadway roof stratum. It is concluded that the break roof angle is an important factor influencing the stability of gob-side entry retaining surrounding rock. This paper studies the stress distribution characteristics and plastic damage scope of gob-side entry retaining integrated coal seams, as well as the roof strata migration law and the supporting stability of caving structure filled on the break roof layer at the break roof angles of $-5^{\circ}$, $0^{\circ}$, $5^{\circ}$, $10^{\circ}$ and $15^{\circ}$ are studied. The simulation results of numerical analysis indicate that, the stress concentration and plastic damage scope to the sides of gob-side entry retaining integrated coal at the break roof angle of $5^{\circ}$ are reduced and shearing stress concentration of the caving filling body has been eliminated. The disturbance of coal mining to the roadway roof and loss of carrying capacity are mitigated. Field tests have been carried out on air-return roadway 5203 with the break roof angle of $5^{\circ}$. The monitoring indicates that the break roof filling section and compaction section are located at 0-45 m and 45-75 m behind the working face, respectively. The section from 75-100 m tends to be stable.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.252-259
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• 2008

The deep-sea mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. The mining system can be regarded as a large-scale system in which each subsystem is interconnected to other ones. In order to control a large-scale system, decentralized control approaches have been proposed recently. In this paper, as a basic study on application of decentralized control, firstly, the mining system was modeled in a simplified way. Lifting system and buffer were regarded as a spherical pendulum and the flexible pipe was taken as a two-dimensional linear spring connection. Based on the simplified model dynamics, the mining system can be decentralized two subsystems, the one consisting of surface vessel, lifting system and buffer, and the other, the miner. Next, this paper proposed the design of controller for each decentralized subsystem by regarding the interacting terms as disturbances. The controllers kept the constant distance between two subsystems during the miner was moving on the specified track. Finally, the efficiency of proposed controller was proven through the numerical simulation of the derived model.

• Journal of Information Technology Applications and Management
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• v.15 no.4
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• pp.21-36
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• 2008

As the great disturbance from abusing credit cards in Korea becomes stabilized, credit card companies need to interpret credit-card delinquents classification models from the viewpoint of profit. However, hit ratio which has been used as a measure of goodness of classification models just tells us how much correctly they classified rather than how much profits can be obtained as a result of using classification models. In this research, we tried to develop a new utility-based measure from the viewpoint of profit and then used this new measure to analyze two classification models(Neural Networks and Decision Tree models). We found that the hit ratio of neural model is higher than that of decision tree model, but the utility value of decision tree model is higher than that of neural model. This experiment shows the importance of utility based measure for credit-card delinquents classification models. We expect this new measure will contribute to increasing profits of credit card companies.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1715-1723
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• 2018

This work investigates the performance of fully complex- valued radial basis function network(FC-RBF) and complex extreme learning machine (CELM) based neural approaches for classification of power quality disturbances. This work engages the use of S-Transform to extract the features relating to single and combined power quality disturbances. The performance of the classifiers are compared with their real valued counterparts namely extreme learning machine(ELM) and support vector machine(SVM) in terms of convergence and classification ability. The results signify the suitability of complex valued classifiers for power quality disturbance classification.

• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.415-420
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• 2022

It is essential that continual assessments of the impact of mine-derived water as a long-lasting burden on freshwater environments. Abundance-based evaluations of benthic macroinvertebrates have been conducted to evaluate anthropogenic disturbances and devise policies to reduce their impact. In this study, the status of a stream habitat was evaluated based on the body length and biomass weight of benthic macroinvertebrates of the family Baetidae. Following the renewal of the mining water treatment plant, the abundance of Baetidae assemblages recovered to a level comparable to that of a reference site. However, relatively low values were found for both body length and biomass weight in Baetidae species inhabiting the reddened streambed area, suggesting that the habitat has not yet been completely recovered despite the recovery of the abundance of the Baetidae assemblages. Therefore, continuous investigation and evaluation of this disturbed stream are necessary until their growth conditions of the habitat have functionally recovered.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.265-274
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• 2017

This paper examines the problems of big data analysis education and suggests ways to solve them. Big data is a trend that the characteristic of big data is evolving from V3 to V5. For this reason, big data analysis education must take V5 into account. Because increased uncertainty can increase the risk of data analysis, internal and external structured/semi-structured data as well as disturbance factors should be analyzed to improve the reliability of the data. And when using opinion mining, error that is easy to perceive is variability and veracity. The veracity of the data can be increased when data analysis is performed against uncertain situations created by various variables and options. It is the node analysis of the textom(텍스톰) and NodeXL that students and researchers mainly use in the analysis of the association network. Social network analysis should be able to get meaningful results and predict future by analyzing the current situation based on dark data gained.