• Earthquakes and Structures
• /
• v.3 no.2
• /
• pp.141-168
• /
• 2012

The Retrofit Yield Spectrum (RYS) is a new spectrum-based device that relates seismic demand of a retrofitted structure with the fundamental design parameters of the retrofit. This is obtained from superposition of Yield Point Spectra with design charts that summarize in pertinent spectrum-compatible coordinates the attributes of a number of alternative retrofit scenarios. Therefore, once the requirements for upgrading a given structure have been determined, the RYS enable direct insight of the sensitivity of the seismic response of the upgraded structure to the preliminary design decisions made while establishing the retrofit plan. By virtue of their spectrum-based origin, RYS are derived with reference to a single mode of structural vibration; a primary objective is to control the contribution of this mode in the retrofit design so as to produce a desirable distribution of damage at the ultimate limit state by removing soft storey formations and engaging the maximum number of structural members in deformation, in response to the input motion. Calculations are performed with reference to the yield-point, where secant stiffness is proportional to the flexural strength of reinforced concrete members. Derivation and use of the Retrofit Yield Spectra (RYS) refers to the seismic demand expressed either in terms of spectral acceleration, spectral displacement or interstory drift, at yield of the first storey. A reinforced concrete building that has been tested in full scale to a sequence of simulated earthquake excitations is used in the paper as a demonstration case study to examine the effectiveness of the proposed methodology.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.4
• /
• pp.317-328
• /
• 2013

In this paper, the optimization has been performed to design a multi-layer structure that is used as a structure for noise reduction of acoustic sonar sensors in underwater vehicles. Two design goals are considered to reduce self-noise from own machineries and to enhance acoustic signals detected from outside. Both distinct and continuous design parameters have been used such as selection of material properties of each layer and thickness of each layer, respectively. The sensitivity of design parameters has been analyzed and the evolutionary algorithm has been implemented for design optimization. For design optimization process, each of the design goals and the two combined design goals have been considered to analyze the achievement of those design goals.

• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.429-438
• /
• 2017

Structural design has an imperative role in deciding the failure possibility of a Reinforced Concrete (RC) structure. Recent research works achieved the goal of predicting the structural failure of the RC structure with the assistance of machine learning techniques. Previously, the Artificial Neural Network (ANN) has been trained supported by Particle Swarm Optimization (PSO) to classify RC structures with reasonable accuracy. Though, keeping in mind the sensitivity in predicting the structural failure, more accurate models are still absent in the context of Machine Learning. Since the efficiency of multi-objective optimization over single objective optimization techniques is well established. Thus, the motivation of the current work is to employ a Multi-objective Genetic Algorithm (MOGA) to train the Neural Network (NN) based model. In the present work, the NN has been trained with MOGA to minimize the Root Mean Squared Error (RMSE) and Maximum Error (ME) toward optimizing the weight vector of the NN. The model has been tested by using a dataset consisting of 150 RC structure buildings. The proposed NN-MOGA based model has been compared with Multi-layer perceptron-feed-forward network (MLP-FFN) and NN-PSO based models in terms of several performance metrics. Experimental results suggested that the NN-MOGA has outperformed other existing well known classifiers with a reasonable improvement over them. Meanwhile, the proposed NN-MOGA achieved the superior accuracy of 93.33% and F-measure of 94.44%, which is superior to the other classifiers in the present study.

• Journal of the Korean Society for Railway
• /
• v.12 no.6
• /
• pp.1024-1029
• /
• 2009

According to increase of massive concrete structures, Thermal crack done by heat of hydration have been increased in a process of the execution. In case of a subway concrete box structure, thickness of structures are almost over 1 meter, and penetrating crack by external restraint takes a bad effect on the durability with a water leakage and deterioration in especially concrete wall. A try of shortening a constructing period often occurs as subway is generally constructed according to a road to decrease a traffic jam. The research proposes executing method by skipping one block as a plan of shortening a constructing period and investigate an influence on thermal cracking control. Additionally, sensitivity analysis is accomplished by changing a height of a concrete wall, and concrete placing and air temperature met with a field condition.

• Proceeding of KASS Symposium
• /
• 2008.05a
• /
• pp.107-112
• /
• 2008

This paper investigates the variation of post-buckling behaviours of 2-dimensional shallow arch type truss after sizing optimization. The mathematical programming technique is used to produce the optimum member size of 2D arch truss against a central point load. Total weight of structure is considered as the objective function to be minimized and the displacement occurred at loading point and member stresses of truss are used as the constraint functions. The finite difference method is used to calculate the design sensitivity of objective function with respect to design variables. The postbuckling analysis carried out by using the geometrically nonlinear finite element analysis code ISADO-GN. It is found to be that there is a huge change of post-buckling behaviour between the initial structure and optimum structure. Numerical results can be used as useful information for future research of large spatial structures.

• Journal of the Korea Furniture Society
• /
• v.25 no.2
• /
• pp.79-86
• /
• 2014

Furniture can be a product of design and is considered a form of a decorative art. Architectural works are often perceived as cultural symbols and as works of art. Korean traditional architectural form and wooden furniture were improved by adding up an organic coordination in the interior space. Furniture adds beauty of life by being coordinated with the interior space with its particular characteristic in the form of architectural structure. Architecture and furniture are also being improved in a more natural and diverse way. Therefore, in this research, from the choice of the location, Korean traditional architecture is considered to be coordinated with the nature, and the technical skill is lessened to express its beauty. There is a presence of elegance yet robust combination of simplicity and beauty. In addition, the traditional architecture and wooden furniture are completely expressed structurally with coordination of the outstanding design and solid structure according to the thrifty living in the Confucian ideas which influenced the Korean traditional society. The representative of Korean traditional architecture, Baeheulrim pillar, has worked as motive because of its visual comfort caused by optical illusion and formative elements. The small portable dining table (Soban) which reflects the characteristic of Korean unique tradition and the sensitivity of Koreans has been reinterpreted through the motive in this research. As a result, it has shown the possibility as the design element to change the aesthetic structure. In the modern society, cultural identity plays a vital role. Therefore, this research can be used as reference for the new concept of furniture - making. It could be a combination of modern people, lifestyle and living space by creating the Korean image suitable for the modern society.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.3
• /
• pp.145-153
• /
• 2016

Cable TV with largest subscription base in pay TV market has difficulty in managing the task of digital switch over. This study analyzed the factors in delay of cable TV switch over and examined the impact of pay TV market structure and competition. The delaying factors turned out to be the lack of incentives and resources of cable TV operators, insufficient policy measures and acceptance tolerance issues of subscribers. Since cable TV operators with monopolistic status in pay TV market had continuous profit from analog service, they were not responsive to digital switch over which requires additional investment. Policy measures including support for the low income household and mandatory cut-off point for stopping analog broadcasting. Subscriber's willingness to accept digital broadcasting in terms of price sensitivity and preference for convenient operation also played a role. Introduction of IPTV in pay TV market influenced the speed of digital switch over of cable TV operators. MSOs with economies of scale showed higher digital switch over rate than independent SO.

• Korean Journal of Psychosomatic Medicine
• /
• v.15 no.2
• /
• pp.88-92
• /
• 2007

Objective : Tellegen Absorption Scale(TAS) is an instrument intended to assess hypnotizability and designed to sample absorbing and self-altering experiences, including dissociative experiences. The present study attempted to identify the internal structure of TAS. Methods : One hundred and thirty nine undergraduates completed the Korean version of Tellegen Absorption Scale(TAS-K). Cronbach's alpha was calculated and factor analyses were done. Results : An exploratory principal-components analysis yielded three factors accounting for 31.06% of variance. Factor 1 included dissociative(dissociation-like) experiences, factor 2 tapped imaginative involvements, and factor 3 had to do with perceptual sensitivity. Conclusion : TAS-K may include absorbing and self-altering experiences.

• Advances in aircraft and spacecraft science
• /
• v.1 no.2
• /
• pp.233-251
• /
• 2014

Each aircraft have to be certified for a specified level of impact energy, for assuring the capability of a safe flight and landing after the impact against a bird at cruise speed. The aim of this research work was to define a scientific and methodological approach to the study of the birdstrike phenomenon against several windshield geometries. A series of numerical simulations have been performed using the explicit finite element solver code LS-Dyna, in order to estimate the windshield-surround structure capability to absorb the bird impact energy, safely and efficiently, according to EASA Certification Specifications 25.631 (2011). The research considers the results obtained about a parametric numerical analysis of a simplified, but realistic, square flat windshield model, as reported in the last work (Grimaldi et al. 2013), where this model was subjected to the impact of a 1.8 kg bird model at 155 m/s to estimate the sensitivity of the target geometry, the impact angle, and the plate curvature on the impact response of the windshield structure. Then on the basis of these results in this paper the topic is focused about the development of a numerical simulation on a complete aircraft windshield-surround model with an innovative configuration. Both simulations have used a FE-SPH coupled approach for the fluid-structure interaction. The main achievement of this research has been the collection of analysis and results obtained on both simplified realistic and complete model analysis, addressed to approach with gained confidence the birdstrike problem. Guidelines for setting up a certification test, together with a design proposal for a test article are an important result of such simulations.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.1920-1925
• /
• 2007

A transformer is a device that changes the current and voltage by electricity induced between coil and core steel, and it is composed of metals and insulating materials. In the core of the transformer, the thermal load is generated by electric loss and the high temperature can make the break of insulating. So we must cool down the temperature of transformer by external radiators. According to cooling fan's usage, there are two cooling types, OA(Oil Natural Air Natural) and FA(Oil Natural Air Forced). For this study, we used Fluent 6.2 and analyzed the cooling characteristic of radiator. we calculated 1-fin of detail modeling that is similar to honeycomb structure and multi-fin(18-fin) calculation for OA and FA types. For the sensitivity study, we have different positions(side, under) of cooling fans for forced convection of FA type. The calculation results were compared with the measurement data which obtained from 135.45/69kV ultra transformer flowrate and temperature test. The aim of the study is to assess the Fluent code prediction on the radiator calculation and to use the data for optimizing transformer radiator design.