• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.4
• /
• pp.301-308
• /
• 2016

In this study, a novel method referred as non-marker vision-based displacement measuring system(NVDMS) was introduced in order to measure the displacement of structure. There are two distinct differences between proposed NVDMS and existing vision-based displacement measuring system(VDMS). First, the NVDMS extracts the pixel coordinates of the structure using a feature point not a marker. Second, in the NVDMS, the scaling factor in order to convert the coordinates of a feature points from pixel value to physical value can be calculated by using the external conditions between the camera and the structure, which are distance, angle, and focal length, while the scaling factor for VDMS can be calculated by using the geometry of marker. The free vibration test using the three-stories scale model was conducted in order to analyze the reliability of the displacement data obtained from the NVDMS by comparing the reference data obtained from laser displacement sensor(LDS), and the measurement of dynamic characteristics was proceed using the displacement data. The NVDMS can accurately measure the dynamic displacement of the structure without the marker, and the high reliability of the dynamic characteristics obtained from the NVDMS are secured.

• Journal of the Korean Society for Railway
• /
• v.17 no.4
• /
• pp.233-244
• /
• 2014

In this study, an analysis method for maglev train-guideway interaction is verified using field measurement data. The cabin and bogies of the maglev train are modeled as rigid bodies that are allowed to have heave and pitch motions. Levitation forces from the electromagnetic suspensions on the bogies are controlled using an active control algorithm. The guideway is represented using the Euler-Bernoulli beam. Considering rigorously the changes in air-gaps and material points at which the levitation forces are applied due to the pitch motions of the bogies, dynamic analysis of maglev train-guideway interaction is performed. Using field measurement data, obtained from the Incheon Airport Maglev Railway, the analysis method is verified. Accuracy of the analysis method is investigated. It is determined that the structures in the railway are designed and constructed safely according to the design code for maglev railways.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.2
• /
• pp.75-85
• /
• 2003

Laboratory model blast and in-situ rock blast tests were conducted to determine blast-induced stress wave propagation characteristics under different explosive types, different loading conditions and different mediums. Dynamic numerical approaches were conducted under the same conditions as experimental tests. Stress magnitudes at mid-point between two blast holes which were detonated simultaneously increased up to two times those of single hole detonation. The rise time of maximum stress in a decoupled charge condition was delayed two times that of a fully charged condition. Dynamic numerical analysis showed almost similar results to blast test results, which verifies the effectiveness of numerical approaches fur optimizing the tunnel blast design. Dynamic numerical analysis was executed to evaluate rock behavior and damage of the contour hole, the sloping hole adjacent to the contour hole in the road tunnel blasting pattern. The rock damage zone of the sloping hole from the numerical analysis was larger than that of the contour hole. Damage in the sloping hole can be reduced by using lower density explosive, by applying decoupled charge, or by increasing distance between the sloping hole and the contour hole.

• The Korean Journal of Applied Statistics
• /
• v.29 no.4
• /
• pp.559-569
• /
• 2016

A long-run relationship of stock, monetary, realty markets, and business conditions has been suggested to exist due to internal and external shocks. This study investigates whether such a relationship really exists and then performs statistical tests to discern features of the long-run adjustment processes from short-run discrepancies because it is difficult to find studies that examine the market relationship. The comovement relationship of the whole market does not appear to hold for the entire study period; however, it is found to exist for the period before the financial crisis. Estimated error correction models show consistently declining equilibrium errors each period that suggests a recovering process of the long-run equilibrium from short-run secessions.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.5
• /
• pp.539-548
• /
• 2007

This paper deals with flexural-torsional free vibrations of the circular strip foundation with the variable breadth on Pasternak soil. The cross-section of the strip foundation is chosen as the rectangular one with the constant thickness and variable breadth, which is symmetrical about the mid-arc. Also, the foundation that supports the circular strip is modeled as the Pasternak soil with the shear layer. Ordinary differential equations accompanying the boundary conditions are derived. In the governing equations, the transverse, rotatory and torsional inertias are included. These equations are solved numerically and four lowest frequencies are obtained. In the numerical results, the effects of foundation parameters on frequencies are extensively investigated. It is expected that the theories and numerical results of this study can be used in the dynamic design of strip foundations.

• Journal of Korean Society of Transportation
• /
• v.28 no.5
• /
• pp.107-116
• /
• 2010

The vehicle travel time between locations in a downtown is greatly influenced by both complex road conditions and traffic situation that changes real time according to various external variables. The customer's demands also stochastically change by time period. Most vehicle routing problems suggest a vehicle route considering travel distance, average vehicle speed, and deterministic demand; however, they do not consider the dynamic external environment, including items such as traffic conditions and stochastic demand. A realistic vehicle routing problem which considers traffic (smooth, delaying, and stagnating) and stochastic demands is suggested in this study. A mathematical programming model and hybrid genetic algorithm are suggested to minimize the total travel time. By comparing the results considering traffic and stochastic demands, the suggested algorithm gives a better solution than existing algorithms.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.6
• /
• pp.521-537
• /
• 2000

Ultrasonic imaging is the most widely used modality among modern imaging device for medical diagnosis and the system performance has been improved dramatically since early 90's due to the rapid advances in DSP performance and VLSI technology that made it possible to employ more sophisticated algorithms. This paper describes "main stream" digital signal processing functions along with the associated implementation considerations in modern medical ultrasound imaging systems. Topics covered include signal processing methods for resolution improvement, ultrasound imaging system architectures, roles and necessity of the applications of DSP and VLSI technology in the development of the medical ultrasound imaging systems, and array signal processing techniques for ultrasound focusing.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.260-266
• /
• 2017

The global economy, including Korea, has continuously searched for various market-friendly policies and new economic systems in pursuit of the forth industrial revolution. As a result, economic markets have grown, and factors affecting markets have diversified. Therefore, as for many company's decision makers, it has become an important issue to analyze and forecast markets accurately and effectively for rapid and appropriate decision making. In this study, we aim to improve the accuracy and validity of forecast models by applying extended information criteria in existing restricted information criteria to determine optimized modeling for the accurate analysis and prediction of complex market environments. In order to verify the practical use of the extended information criteria adopted in this study, we compare this study employing KOSPI data with previous studies. Experimental results show that applying extended information criteria is more accurate than using the existing information criteria.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.9
• /
• pp.49-60
• /
• 2017

The purpose of this study is to investigate the behavior of a single batter pile with repeated lateral loading through model tests. Repeated loads were applied in one direction and two directions, and lateral resistance and bending moment were analyzed by varying the relative density of the ground. As a result, lateral resistance and maximum bending moment were increased in the order of Out batter, Plumb, and In batter when one-way and two-way dynamic lateral loads were applied. The depth at the maximum bending moment was more deeper with the loading. The moments at bottom layer were decreased in the order of Out batter, Plumb, and In batter but upper moments were increased with the same order. Also, various bottom and upper moments were small when the two-way dynamic lateral load was applied compared to one-way lateral load.

• Journal of the Korean Geotechnical Society
• /
• v.36 no.6
• /
• pp.17-34
• /
• 2020

In response spectrum analysis of pile-supported structure, an amplified seismic wave should be used as the input ground acceleration through the site-response analysis. However, each design standard uses different input ground acceleration criteria, which leads to confusion in determining the appropriate input ground acceleration. In this study, the ground accelerations were calculated through dynamic centrifuge model test, and the response spectrum analysis was performed using the calculated ground acceleration. Then, the moments derived from the test and analysis were compared, and a method for determining the appropriate input ground acceleration in response spectrum analysis was presented. Comparison of the experimental and simulated results reveals that modeling of the ground using elastic springs allows proper simulation of the natural period of the structure, and the use of a seismic wave that is amplified at the ground surface as the input ground acceleration provided the most accurate results for the response analysis of pile-supported structures in sands.