• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.55-66
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• 2021

ICAO recommended that airspace monitoring and periodic safety assessments in each Contracting State ensure the stability of the airspace, since reducing the aircraft lateral and vertical separation intervals would rather increase the risk of collision. The target level of safety of the AKARA-FUKUE Corridor at the southern end of Jeju was 247×10^-9. In simple comparison, this means that the risk of an aircraft collision in this area (international safety standards, 5.0×10^-9) is about 50 times higher. The scope of this study is to organize the concept of terms, analyze the air traffic volume, the current status of navigational safety facility usage fees, and investigations of an aircraft collision risk in Jeju southern air corridor. Analyzing government policies and overseas evaluations, revising some of the existing contents, presenting some of the additional contents of new routes, and changing the instrument procedure for Korean-Chinese routes, change of arrive/departure route between Incheon Airport and Shanghai Airport, reduce the risk of aircraft collisions. We hope to restore airspace sovereignty, contribute to policies for the government to take the lead in solving this problem, and expect stability and operational efficiency in air traffic.

• Steel and Composite Structures
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• v.51 no.4
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• pp.417-440
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• 2024

Artificial neural networks (ANN) have been the focus of several studies when it comes to evaluating the pile's bearing capacity. Nonetheless, the principal drawbacks of employing this method are the sluggish rate of convergence and the constraints of ANN in locating global minima. The current work aimed to build four ANN-based prediction models enhanced with methods from the black hole algorithm (BHA), league championship algorithm (LCA), shuffled complex evolution (SCE), and symbiotic organisms search (SOS) to estimate the carrying capacity of piles in cold climates. To provide the crucial dataset required to build the model, fifty-eight concrete pile experiments were conducted. The pile geometrical properties, internal friction angle 𝛗 shaft, internal friction angle 𝛗 tip, pile length, pile area, and vertical effective stress were established as the network inputs, and the BHA, LCA, SCE, and SOS-based ANN models were set up to provide the pile bearing capacity as the output. Following a sensitivity analysis to determine the optimal BHA, LCA, SCE, and SOS parameters and a train and test procedure to determine the optimal network architecture or the number of hidden nodes, the best prediction approach was selected. The outcomes show a good agreement between the measured bearing capabilities and the pile bearing capacities forecasted by SCE-MLP. The testing dataset's respective mean square error and coefficient of determination, which are 0.91846 and 391.1539, indicate that using the SCE-MLP approach as a practical, efficient, and highly reliable technique to forecast the pile's bearing capacity is advantageous.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.7
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• pp.2027-2046
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• 2024

Reconfigurable Intelligent Surface (RIS) is an innovative technique to precisely control the phase of incident signals with the help of low-cost passive reflective elements. It shows excellent potential in the sixth generation of mobile communication systems, which not only extends wireless coverage but also boosts channel capacity. Considering that multipath propagation and a high number of antennas are involved in RIS in assisted mega multiple-input multiple-output (MIMO) systems, it suffers from severe channel fading and multipath effects, which in turn lead to signal instability and degradation of transmission performance. To overcome this obstacle, this essay suggests an improved gradient optimization algorithm to dynamically and optimally adjust the phase of the reflective elements to counteract channel fading and multipath effects as a strategy. In order to overcome the optimization problem of falling into local minima, this paper proposes an adaptive learning rate algorithm based on Adagrad improvement, which searches for the global optimal solution more efficiently and improves the robustness of the optimization algorithm. The suggested technique helps to enhance the estimate of channel efficiency of RIS-assisted large MIMO systems, according to simulation results.

• 한국해양학회지
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• v.11 no.2
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• pp.43-50
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• 1976

The annual nariation of surface heat exchange at ten selected station in the Korean coastal seas was studied using data of monthly mean surface temperature and meteorological parameters averaged for many years. Through heat exchange between the sea and the atmosphere, the surfaces in the Korean coastal seas are warmed by accepting heat from the atmosphere during march to September in the west coast sea, during Aprill to August in the south coast sea which includes the Ulleung-do coast sea and during April to September in the east coast sea. The periods which are cooled by losing heat to the atmosphere correspond to residual months excepting the above warming periods. Maximum total heat exchange during the warming period at each station shows the distribution of 320-720cal/ $\textrm{cm}^2$ day in June to July and during the cooling period shows the distribution of -260∼-940 cal/$\textrm{cm}^2$ day in November to January. The annual average total heat exchange shows warming of 100-240 Cal/$\textrm{cm}^2$ day in the west coast sea, cooling of -90∼-150 Cal/$\textrm{cm}^2$ day in the south coast sea and the Ulleung-do coast sea, and slight warming or cooling of -15∼65 Cal/$\textrm{cm}^2$ day in the east coast sea. Maxima or minima of the surface temperature in the Korean coastal seas appear in the month that the warming or cooling period is ended. The evaporation rate is highest during October to next January with the distribution of 5∼12mm/day.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.19-28
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• 2006

Most conventional model updating methods must use mathematical objective function with experimental modal matrices and analytical system matrices or must use information about the gradient or higher derivatives of modal properties with respect to each updating parameter. Therefore, most conventional methods are not appropriate for complex structural system such as bridge structures due to stability problem in inverse analysis with ill-conditions. Sometimes, moreover, the updated model may have no physical meaning. In this paper, a new FE model updating method based on a hybrid optimization technique using genetic algorithm (GA) and Holder-Mead simplex method (NMS) is proposed. The performance of hybrid optimization technique on the nonlinear problem is demonstrated by the Goldstein-Price function with three local minima and one global minimum. The influence of the objective function is evaluated by the case study of a simulated 10-dof spring-mass model. Through simulated case studies, finally, the objective function is proposed to update mass as well as stiffness at the same time. And so, the proposed hybrid optimization technique is proved to be an efficient method for FE model updating.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.05
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• pp.65-70
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• 1991

A hybrid model which uses a probabilistic model and a MLP(multi layer perceptron) model for pattern recognition of EMG(electromyogram) signals is proposed in this paper. MLP model has problems which do not guarantee global minima of error due to learning method and have different approximation grade to bayesian probabilities due to different amounts and quality of training data, the number of hidden layers and hidden nodes, etc. Especially in the case of new test data which exclude design samples, the latter problem produces quite different results. The error probability of probabilistic model is closely related to the estimation error of the parameters used in the model and fidelity of assumtion. Generally, it is impossible to introduce the bayesian classifier to the probabilistic model of EMG signals because of unknown priori probabilities and is estimated by MLE(maximum likelihood estimate). In this paper we propose the method which get the MAP(maximum a posteriori probability) in the probabilistic model by estimating the priori probability distribution which minimize the error probability using the MLP. This method minimize the error probability of the probabilistic model as long as the realization of the MLP is optimal and approximate the minimum of error probability of each class of both models selectively. Alocating the reference coordinate of EMG signal to the outside of the body make it easy to suit to the applications which it is difficult to define and seperate using internal body coordinate. Simulation results show the benefit of the proposed model compared to use the MLP and the probabilistic model seperately.

• Korean Journal of Ichthyology
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• v.3 no.1
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• pp.24-35
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• 1991

Fish larvae were collected monthly from coastal water around Hamduck, northern part of Cheju Island from April 1989 to March 1990. During the study period, a total of sixty four species, representing 35 genera and 27 families, were observed, of these 4 species appeared to be major groups which comprised about 66% of total fish larvae abundance, including Ammodytes personatus (February-March), Scomber japonicus(September-March), Enneapterygius etheostomus(June-September), and Engraulis japonica(August-November). Seasonally, the maximun numbers of species and individuals appeared in summer and in spring, and in summer, respectively, while the minima numbers of species and individuals appeared in winter. Inshore species were composed of 44 species(62.9%) and 557 individuals(70.4%), which were much higher both in the species numbers and individuals than those of offshore species.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.269-275
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• 2014

A survey was conducted to identify the occurrence of problematic weed species on the Dioscorea oppostifolia fields in South Korea. Total 43 sites of the 8 different regions in S. Korea were investigated from May to October, 2014. In yam fields, the identified weeds were distributed in 11 families and 44 species. The exotic plants were identified as 3 families, 10 genera, 10 species. The vegetation of Dioscorea oppostifolia fields was classified into communities of 7 groups by methods of the Zurich-Montpellier school of phytosociology (Xanthium canadense Community, Bidens frondosa Community, Echinochloa oryzoides Community, Eclipta prostrata Community, Portulaca oleracea Community, Centipeda minima Community, Rorippa islandica Community). The weeds occurred in Dioscorea oppostifolia fields were divided into three groups in principal component plot analysis (PCA). Without weed control, yields loss in yam production was reached up to 82% as compared to weed controlled fields.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.1
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• pp.41-50
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• 2003

The feasibility as floricultural crops and water garden plant materials of Korean native water plants was investigated. Propagation type, growing and flowering time were observed for development as water garden, interior aquarium plant and water purification materials. Flowering time of the water plant was 7 species in May, 28 species in June, 49 species in July, 55 species in August, 47 species in September, and 17 species in October. Beautiful flowering water plants were Nymphaeaceae, Nymphoides peltata, Nymphoides indica, Monochoria korsakowii, Iris pseudacorus, Iris laevigata, and etc. Ornamental leafy water plants were Ceratopteris thalictroides, Ludwigia ovalis, Myriophyllum verticillatim, Limnophila sessiliflora, Blyxa aubertii, Blyxa echinosperma, Vallisneria asiatica, Hydrilla verticillata and Eleocharis acicularis etc. Isoetes japonica, Isoetes coreana and Isoetes sinensis were propagated by spore. Blyxa aubertii, Blyxa echinosperma, Myriophyllum verticillatim, Nuphar japonicum, Nelumbo nucifera, Ottelia alismoides, Sagittaria aginashi, Trapa japonica, and Trapa natans were propagated by seed. Persicaria amphibia, Ceratophyllum demersum (hornwort), Myriophyllum verticillatim, Myriophyllum spicatum, Oenanthe javanica, Potamogeton crispus, Hydrilla verticillata and Acorus calamus were propagated by division. And Vallisneria asiatica, Hydrilla verticillata and Phragmites japonica were propagated by runner. Ceratophyllum demersum (hornwort), Myriophyllum verticillatim, Myriophyllum spicatum, Limnophila sessilifera were propagated by adventitious bud. Ceratopteris thalictroides was propagated by leaf cutting. The 35 genera, 68 species of water plants were available for horticultural use. The 45 species such as Iris laevigata, Eleocharis acicularis, Menyanthes trifoliata, Nymphaea minima, Nuphar pumilum, Nymphoides coreana, Nymphoides peltata, Nymphoides indica, Nymphaea tetragona (water lily), and Typha latifolia could be use for water garden plant. The 21 species such as Limnophila sessilifera, Vallisneria asiatica, Ceratophyllum demersum and Hydrilla verticillata available for indoor aquarium. The 19 species such as Ottelia alismoides, Oenanthe javanica, Limnophila sessilifera and Blyxa echinosperma could be culture in container. The 27 species such as Trapa japonica, Trapa incisa, Phramites commuris (reed), Phragmites japonica, and Zizania latifolia were usable for water purification plant materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1825-1830
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• 2014

Environmental emission of recent automobile is drastically enhanced that it is one of the obvious assignments of exhaust system. This study is a purpose to establish of influence distribution on maxima and minima through the location of pressure on exhaust variable valve. The experiment are checked with real angles using camera which exhaust variable valve is opened side of point. Data has extracted to opening angles with internal flow, pressure. Exhaust variable valve through the floating analysis was analyzed the characteristic of location point about pressure and velocity. The pressures indicated the reduced results internal pressure within muffler. The velocity indicated an opposite results and vibration state of valve was verified to be operated as high speed from lower section. The conclusion to obtain from this study was found out the result to make the optimum back pressure condition as more increasing pressure distribution on valve face if the velocity location attracted by bottom point in order to improve for engine performance.