• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.2
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• pp.71-86
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• 2022

The water quality index (WQI) has been widely used to evaluate marine water quality. The WQI in Korea is categorized into five classes by marine environmental standards. But, the WQI calculation on huge datasets is a very complex and time-consuming process. In this regard, the current study proposed machine learning (ML) based models to predict WQI class by using water quality datasets. Sihwa Lake, one of specially-managed coastal zone, was selected as a modeling site. In this study, adaptive boosting (AdaBoost) and tree-based pipeline optimization (TPOT) algorithms were used to train models and each model performance was evaluated by metrics (accuracy, precision, F1, and Log loss) on classification. Before training, the feature importance and sensitivity analysis were conducted to find out the best input combination for each algorithm. The results proved that the bottom dissolved oxygen (DO_Bot) was the most important variable affecting model performance. Conversely, surface dissolved inorganic nitrogen (DIN_Sur) and dissolved inorganic phosphorus (DIP_Sur) had weaker effects on the prediction of WQI class. In addition, the performance varied over features including stations, seasons, and WQI classes by comparing spatio-temporal and class sensitivities of each best model. In conclusion, the modeling results showed that the TPOT algorithm has better performance rather than the AdaBoost algorithm without considering feature selection. Moreover, the WQI class for unknown water quality datasets could be surely predicted using the TPOT model trained with satisfactory training datasets.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.6
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• pp.180-191
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• 2020

This study analyzes factors that affect average daily travel time budgets, using the Time Use Survey data from 1999 to 2014 in Seoul. We first developed multivariate regression models for travel time from each year, considering demographic and socio-economic variables as well as non-home activity time. The model results showed that household and personal characteristics and non-home activities significantly affect travel time, and their effects are different over time. In addition, we developed seemingly unrelated regression (SUR) models for time allocation for non-home activity and travel, considering their correlations, and explanatory variables were compared over time. Overall, demographic and socio-economic variables significantly affect travel time as well as non-home activity time.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.97-108
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• 2023

Two carbonaceous adsorbents CAT and CARBOPAL were tested for reducing the concentration of the three herbicides in water: 2,4-D (2,4-dichlorophenoxyacetic acid), TCP (2,4,6-trichlorophenol) and metolachlor. Textural and chemical characterization of the adsorbents include nitrogen isotherms, FTIR, titration and thermogravimetric analyses. Adsorption was studied in discontinuous adsorption experiments at different pH values. The experimental adsorption isotherms data were fitted to four theoretical models. Adsorbent characterization reveals that CAT has higher micropore area, lower pore diameter and lower acidity than CARBOPAL. The adsorption is a second-order process and the isotherms best fitted to Sips model. The efficiency of the process depends mainly on the charge of the adsorbate for TCP and 2,4-D, but it depends on the charge of the surface for metolachlor. Adsorption capacity is higher on CAT for 2,4-D and TCP (small molecules), and it is higher on CARBOPAL for metolachlor (large molecules). Theoretical calculations clearly support this assumption.

• Biomolecules & Therapeutics
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• v.31 no.5
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• pp.536-543
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• 2023

Phytoceramide (Pcer) is found mainly in plants and yeast. It can be neuroprotective and immunostimulatory on various cell types. In this study, the therapeutic effect of Pcer was explored using the carrageenan/kaolin (C/K)-induced arthritis rat model and fibroblast-like synoviocytes (FLS). Pcer treatment (1, 10, and 30 mg/kg/day) were given to the arthritic rats for 6 days after disease induction. Weight distribution ration (WDR), knee thickness, squeaking score, serum levels of proinflammatory mediators, and histological analysis were measured and performed to evaluate arthritic symptoms in the rat model. In interleukin (IL)-1β-stimulated FLS, proinflammatory mediators were measured after Pcer (1-30 µM) treatment. Arthritic symptoms in rats with Pcer treatment were significantly decreased at days 4 to 6 after C/K arthritis induction. Inflammation in the knee joints were also significantly decreased in rats with Pcer treatment. Furthermore, in IL-1β-stimulated FLS, the expressions of proinflammatory mediators were also inhibited by Pcer. As shown by the results, Pcer has anti-arthritic effects in the C/K rat model and in synovial cells, suggesting that Pcer has the potential to be a useful agent in arthritis treatment.

• Journal of Korean Association for Spatial Structures
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• v.3 no.4 s.10
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• pp.85-92
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• 2003

In this work, a finite element model is presented for geometrically non-linear analysis of shell structures. Finite element by using a three-node flat triangular shell element is formulated. The non-linear incremental equilibrium equations are formulated by using an updated Lagrangian formulation and the solutions are obtained with the incremental/iterative Newton-Raphson method and arc length method. Some of results are presented for shell structures. The obtained results are in good agreement with the results available in existing literature.

• Journal of Korean Association for Spatial Structures
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• v.3 no.4 s.10
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• pp.77-84
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• 2003

Tensegrity systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts and cables. But there are some difficulties concerning surface stability, surface formation and construction method. One of the ways to solve this problem reasonably is combination of tesile members and rigid members. This structure is a type of flexible strutural system which is unstable initially because the cable material has little initial rigidity. Therefore tensegrity structure need to be introduced to the Initial stress for the self-equilibrated system having stable state. The rigidification of tensegrity systems is related to selfstress states which can be achieved only when geometrical and mechanical requirements are simultaneously satisfied. In this paper, for the stabilization of tesnsegrity structure it is proposed the modified self-equilibrated equation and the range of the various geometrical parameter about unit system. And we generate the model of double layed single curvature arch using the new squew quadruplex unit system.

• Bulletin of the Society of Naval Architects of Korea
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• v.22 no.3
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• pp.19-26
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• 1985

This paper deals with the representation and fairing of ship hull using a B-spline surface which is known as a 3-D model in computer aided free-form design. The first part of this paper is devoted to the fundamental concepts of B-spline theory and its geometrical characteristics. In its second part are described the facillities for efficient application, fast rendering of B-spline surface, and intersection of B-spline surfaces. The examples are presented with actual application to a real ship in the last part. And also a new concept of evaluating the surface fairness by the Gaussian curvature isolines is briefly discussed and its examples are presented.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.23-31
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• 2003

A novel 3D shape optimization algorithm is presented for electromagnetic devices carry-ing eddy current. The algorithm integrates the 3D finite element performance analysis and the steepest descent method with design sensitivity and mesh relocation method. For the design sensitivity formula, the adjoint variable vector is defined in complex form based on the 3D finite element method for eddy current problems. A new 3D mesh relocation method is also proposed using the deformation theory of the elastic body under stress to renew the mesh as the shape changes. The design sensitivity f3r the sur-face nodal points is also systematically converted into that for the design variables for the parameterized optimization application. The proposed algorithm is applied to the optimum design of the tank shield model of the transformer and the effectiveness is proved.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.75-82
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• 2007

Building costs means capital costs which include cost of land, cost of acquiring and preparing the site, construction costs, engineering fees, furnishings, cost of financing the project, and cost of management required to run and maintenance the building for use. An economic analysis is one of the most important factor to determine the project feasibility. The purpose of the this study is to analysis on the construction cost structure of steel truss stadium.

• Wind and Structures
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• v.4 no.4
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• pp.315-332
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• 2001

Presented herein is a numerical study for evaluating the aerodynamic behaviour of equipped bridge deck sections. In the first part, the method adopted is described, in particular concerning turbulence models, meshing requirements and numerical approach. The validation of the procedure represents the aim of the second part of the paper: the results of the numerical simulation in case of two-dimensional, steady, incompressible, turbulent flow around a realistic bridge deck are compared to the data collected from wind-tunnel tests. In order to demonstrate the influence of the section details and of the partial streamlining of the deck geometry on its aerodynamic behaviour, in the third part of the paper the effect of the fairings and of each item of equipment of the section (such as central barriers, side railings and sidewalks) is evaluated. The study has been applied to the deck section of the Normandy cable-stayed bridge.