• Journal of the Economic Geographical Society of Korea
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• v.24 no.4
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• pp.400-410
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• 2021

This study analyzed the determinants of carbon dioxide emissions through the expanded STIRPAT model using panel data from 16 metropolitan cities and provinces in Korea from 2000 to 2019. After testing cross-sectional dependence and coefficient heterogeneity of panel data, we performed analysis using MG, CCEMG, and AMG estimation methods reflected these characteristics. The results of analysis using the AMG estimation method are as follows. The coefficients of income, population, and energy intensity were statistically significant with a positive sign, but urbanization was statistically insignificant. Reduction of carbon dioxide emissions in Korea can be achieved through an increase in energy efficiency and sustainable economic growth. It is necessary to establish a policy that can contribute to sustainable economic growth by inducing productivity improvement through technology innovation reducing carbon dioxide emissions in the long-term as well as building a low-carbon society through active development of carbon dioxide reduction technology.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.233-243
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• 2010

A method is proposed of estimating Muskingum-Cunge parameters for natural streams using cross-sectional and longitudinal channel geometry and roughness coefficient data. Firstly, for various water-surface levels at a cross section cross-sectional areas and hydraulic radii are calculated. Corresponding discharges are then calculated using Manning's equation. This procedure is repeated for all cross-sections in the reach. Finally, routing parameters are estimated from the calculated cross-sectional area and discharge value pairs by regression analysis. The procedures for estimating Muskingum-Cunge parameters are applied to the South Han River. Flows calculated by Muskingum-Cunge model with estimated parameters showed much better agreement with those by dynamic wave model in peak discharge, time to peak discharge, and normalized RMS errors than those calculated by the HEC-1 Muskingum-Cunge model.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.1-7
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• 2009

The purpose of this study was to compare the stress distributions of NiTi rotary instruments based on their cross-sectional geometries of triangular shape-based cross-sectional design, S-shaped cross-sectional design and modified rectangular shape-based one using 3D FE models. NiTi rotary files of S-shaped and modified rectangular design of cross-section such as Mtwo or NRT showed larger stress change while file rotation during simulated shaping. The stress of files with rectangular cross-section design such as Mtwo, NRT was distributed as an intermittent pattern along the long axis of file. On the other hand, the stress of files with triangular cross-section design was distributed continuously. When the residual stresses which could increase the risk of file fatigue fracture were analyzed after their withdrawal. the NRT and Mtwo model also presented higher residual stresses. From this result, it can be inferred that S-shaped and modified rectangular shape-based files were more susceptible to file fracture than the files having triangular shape-based one.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.591-596
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. Two models are examined: a planar two-dimensional channel, and an axisymmetric tube. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and compared to existing experimental data. Computational results for an axisymmetric tube show that as cross-sectional area falls with a reduction in downstream pressure, flow rate increases and reaches a maximum when the speed index (mean velocity divided by wave speed) is near unity at the point of minimum cross-section area, indicative of wave speed flow limitation or "choking" (flow speed equals wave speed) in previous one-dimensional studies. For further reductions in downstream pressure, flow rate decreases. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is ${\le}$ 2 the area throat is located near the downstream end; as wall taper is increased to ${\ge}$ 3 the constriction moves to the upstream end of the tube. In the planar two-dimensional channel, area reduction and flow limitation are also observed when outlet pressure is decreased. In contrast to the axisymmetric case, however, the elastic wall in the two-dimensional channel forms a smooth concave surface with the area throat located near the mid-point of the elastic wall. Though flow rate reaches a maximum and then falls, the flow does not appear to be choked.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.7-12
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• 2008

The three-dimensional finite element modeling of a composite rotor blade is very hard and requires much computation effort. The efficient method to model a composite beam is necessary for the dynamic and aeroelastic analyses of rotor blades. In this study, the beam modeling method of a composite rotor blade is studied using VABS. The computer program, VABS (Variational Asymptotic Beam Section Analysis), uses the variational asymptotic method to split a 3-D nonlinear elasticity problem into 2-D cross-sectional analysis and 1-D nonlinear beam problem. The VABS can produce the sectional stiffness coefficients of composite rotor blades with various cross section and initial twist/curvatures, and recover the original 3-D distribution of displacement/strain/stress fields. The results of various cross section beams show that VABS gives us the accurate results comparared to commercial codes and does not need much computation effort. It can be concluded that VABS provides the efficient method to establish the FE model of a composite rotor blade.

• Structural Engineering and Mechanics
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• v.4 no.1
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• pp.25-35
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• 1996

This paper describes a continuum variational formulation for design optimization of nonlinear structures in the elastic-plastic domain, where unloading and reloading of the structures are allowed to occur. The Total Lagrangian procedure is used for the description of the structural deformation. The direct differentiation approach is used to derive the sensitivities of the various structural response measures with respect to the design parameters. Since the material goes into the inelastic range and unloading and reloading of the structure are allowed to occur, the structural response is path dependent and an additional step is needed to integrate the constitutive equations. It can be shown, consequently, that design sensitivity analysis is also path-dependent. The theory has been discretized by the finite element technique and implemented in a structural analysis code. Mathematical programming approach is used for the optimization process. Numerical applications on trusses are performed, where cross-sectional areas and nodal point coordinates are treated as design variables. Optimal designs have been obtained and compared by using two different strategies: a two level strategy where the levels are defined accordingly the type of design variables, cross sectional areas or node coordinates, and optimizing simultaneously with respect to both types of design variables.

• The Research Journal of the Costume Culture
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• v.30 no.5
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• pp.675-688
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• 2022

The purpose of this study is to analyze the body type characteristics of tall adult men aged 20 to 69 years to present base material on body dimensions for men's clothing companies. The research method comprised statistical analysis of 3D measurements after selecting items from the 8th Korean human body size survey related to the torso body types of 495 adult men who were at least 178cm tall. As a result, six factors were extracted, and the total explanatory variable of the entire factor was shown to be 80.499%. As a result of cluster analysis using this as an independent variable, three types were derived: Type 1, "a normal body type with an oval cross-sectional shape" (37.6%), with a larger vertical size and an oval chest cross-sectional shape compared to other types; Type 2: a "cylindrical thick body shape" (31.1%), which is the first stage of BMI obesity, with narrow shoulders and a cylindrical shape with a round cross-section; Type 3, "a body shape with broad shoulders and developed chest parts" (31.3%), with a horizontal size similar to Type 2 above the waist, but similar to Type 1 below. The results of this study are expected to be used as a basis for a clothing dimension system and clothing development for tall men reflecting the characteristics of the torso.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1055-1060
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• 2020

This study is a study on the analysis and measurement of the radar cross-sectional area of a miniature aircraft. Radar cross-sectional area for miniature aircraft in advance were analyzed using an electromagnetic analysis tool, and an actual miniature aircraft was manufactured and measured in an anechoic chamber. When measuring, the old model was used as reference data for RCS(radar cross section) characteristics and applied to the test result data of the actual reduced model. The measurement method improved the accuracy of the measurement by applying time gating to remove the influence on the components scattered inside the anechoic chamber. The RCS test results of the reduced model showed relatively high RCS characteristics in the microwave band, as the previous analysis results. In the future, we plan to utilize the method of RCS analysis and measurement for the target of the radar in the VHF(Very High Frequency)/UHF(Ultra High Frequency) band with a relatively large wavelength.

• Advances in Computational Design
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• v.4 no.4
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• pp.381-395
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• 2019

This paper proposes a new approach to model the screw joints of integrated ceilings via the finite element method (FEM). The simulation models consist of the beam elements. The screw joints used in the main bars and cross bars and in the W bars and cross bars are assumed to be rotation springs. The stiffness of the rotation springs is defined according to the technical standards proposed by the National Institute for Land and Infrastructure Management of Japan. By comparing the results of the sheer tests and the simulation models, the effectiveness and efficiency of the simulation models proposed in this paper are verified. This paper indicates the possibility that the seismic performance of suspended ceilings can be confirmed directly via beam element models using FEM if the stiffnesses of the screw joints of the ceiling substrates are appropriately defined. Because cross-sectional shapes, physical properties, and other variables of the ceiling substrates can be easily changed in the models, it is expected that suspended ceiling manufactures will be able to design and confirm the seismic performance of suspended ceilings with different cross-sectional shapes or materials via computers, instead of spending large amounts of time and money on shake table tests.

• Composites Research
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• v.27 no.6
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• pp.207-212
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• 2014

The shape optimization of composite flexbeam sections of a bearingless helicopter rotor is studied using a finite element (FE) sectional analysis integrated with an efficient evolutionary optimization algorithm called particle swarm assisted genetic algorithm (PSGA). The sectional optimization framework is developed by automating the processes for geometry and mesh generation, and the sectional analysis to compute the elastic and inertial properties. Several section shapes are explored, modeled using quadratic B-splines with control points as design variables, through a multiobjective design optimization aiming minimum torsional stiffness, lag bending stiffness, and sectional mass while maximizing the critical strength ratio. The constraints are imposed on the mass, stiffnesses, and critical strength ratio corresponding to multiple design load cases. The optimal results reveal a simpler and better feasible section with double-H shape compared to the triple-H shape of the baseline where reductions of 9.46%, 67.44% and 30% each are reported in torsional stiffness, lag bending stiffness, and sectional mass, respectively, with critical strength ratio greater than 1.5.