• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.438-443
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• 2008

In this paper, segmenting and classifying low contrast defects on flat panel display is one of the key problems for automatic inspection system in practice. Problems become more complicated when the quality of acquired image is degraded by the illumination irregularity. Many algorithms are developed and implemented successfully for the defects segmentation. However, vision algorithms are inherently prone to be dependent on parameters to be set manually. In this paper, one morphological segmentation algorithm is chosen and a technique using frequency domain analysis of input images is developed for automatically selection the morphological parameter. An extensive statistical performance analysis is performed to compare the developed algorithms.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.1
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• pp.44-54
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• 2001

This paper describes the antenna alignment method of the tracking antenna system for LEO satellite. The purpose of the antenna alignment is to reduce the angular error due to the structural alignment and the monopulse null point alignment error. The angular error of 3 axis tracking system is the key performance parameter that should be minimized to accurately track satellite movement. The angular error is analyzed via a simulation and boresight measurement. The simulation is done with formulas to be derived from vector concept for 3-axis movement. The formulas of the structural alignment are verified by comparing the formula result with the field measurement. Also, the angular error due to monopulse null shift is obtained via boresight measurement. Based on the analyzed and measured results, the antenna alignment was performed and was verified via tracking test of operating LEO satellite.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.196-201
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• 2010

Measurement of Quality of Service (QoS) parameters and its statistical analysis becomes a key issue for Mobile WiMAX service providers to manage the converged network efficiently and to support end-to-end QoS. In this paper, we investigate the population distribution of end-to-end one-way delay which is the most important QoS parameter in Mobile WiMAX networks. The samples are analyzed with Chi-Square Goodness-of-Fit test, Kolmogorov-Smirnov (K-S), and Anderson-Darling (A-D) test to verify the distribution of parent population. The relation with confidence level and the minimum number of sample size is also performed for logistic distribution. The statistical analysis is a promising approach for measuring the performance Mobile WiMAX networks.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• Steel and Composite Structures
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• v.13 no.2
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• pp.109-122
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• 2012

An efficient and accurate algorithm is proposed to evaluate the reliability of cable-stayed bridges accounting for soil-pile interaction. The proposed algorithm integrates the finite-element method and the response surface method. The finite-element method is used to model the cable-stayed bridge including soil-pile interaction. The reliability index is evaluated based on the response surface method. Uncertainties in the superstructure, the substructure and load parameters are incorporated in the proposed algorithm. A long span steel cable-stayed bridge with a main span length of 1088 m built in China is considered as an illustrative example. The reliability of the bridge is evaluated for the strength and serviceability performance functions. Results of the study show that when strength limit states for both girder and tower are considered, soil-pile interaction has significant effects on the reliability of steel cable-stayed bridges. Further, a detailed sensitivity study shows that the modulus of subgrade reaction is the most important soil-pile interaction-related parameter influencing the reliability of steel cable-stayed bridges.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1049-1057
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• 2011

Today, most weapon systems operate as component systems of SoS(System of Systems) and they produce synergy effects in the battle field by interoperating. In addition, the acquisition issues on weapon systems have expanded into SoS context including sustainment analysis. Availability is the sustainment KPP(Key Performance Parameter) of weapon systems. In this paper, a simulation model is proposed to analyze the availability of SoS. The simulation model consists of 5 modules: Mission and Task, System, System RBD, Maintenance system and a simulation engine. Then it was implemented and applied to a SoS. As a result of the application, the simulation model could be applied for analyzing the availability of the SoS and provided information about critical tasks and risky component systems to complete the given mission of the SoS.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.209-216
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• 2006

For evaluation of building performance, a nonlinear dynamic capacity of the building is a key parameter. In this study, an reinforced concrete special moment resisting frame building was chosen to study the process of determining the nonlinear dynamic capacity. The building, which was designed by IBC 2003 representing new codes, was composed of special moment resisting frames in the perimeter and internal frames inside the building. The capacity, which is inter-story drift capacity, consists of two categories, local and global collapses. Global collapse capacity was determined by incremental dynamic analysis. Local collapse capacity was determined by the same method except for utilizing damage index. In audition to this, it was also investigated that the effect of including internal frames designed by gravity load in the analysis. Results showed that the damage index is a useful tool for determining local collapse. Furthermore, including the internal frames with special frames in the analysis is very important in determining the capacity of a building so both must be considered at the same time.

• Journal of Applied Reliability
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• v.7 no.3
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• pp.111-118
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• 2007

In 2000, US Army Test and Evaluation Command (ATEC) released the status of reliability requirement levels and achievements for the military equipment which evaluated through the operational tests from 1985 to 1990 and from 1996 to 2000. The rates of military equipments that do not meet reliability requirements are 59% from 1985 to 1990 and 80% from 1996 to 2000. Thus, the US Army has figured out causes, taken steps and put them into practice, This paper is about the recent reliability problems and the latest tendency about US military equipment to acquirere liability level.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.441-448
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• 2023

The quality of the casting process generates the largest source of defects in the manufacturing process, so its management is a key factor in productivity and quality evaluation. Based on the results of factor analysis, correlation analysis, and regression analysis with process data, this study aims to optimize the machine learning model to reduce the defect rate and verify the data suitability for smart factories.

• Wind and Structures
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• v.9 no.2
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• pp.125-146
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• 2006

Stonecutters Bridge of Hong Kong is a cable-stayed bridge with two single-column pylons each 298 m high and an aerodynamic twin deck. The total length of the bridge is 1596 m with a main span of 1018 m. The top 118 m of the tower will comprise structural steel and concrete composite while the bottom part will be of reinforced concrete. The bridge deck at the central span will be of steel whilst the side spans will be of concrete. Stonecutters Bridge has adopted a twin-girder deck design with a wide clear separation of 14.3 m between the two longitudinal girders. Although a number of studies have been conducted to investigate the aerodynamic performance of twin-girder deck, the actual real life application of this type of deck is extremely limited. This therefore triggered the need for conducting the present studies, the main objective of which is to investigate the performance of Stonecutters Bridge against flutter at its in-service stage as well as during construction. Based on the flutter derivatives obtained from the 1:80 scale rigid section model experiment, flutter analysis was carried out using 3-D finite element based single parameter searching method developed by the second author of this paper. A total of 6 finite element models of the bridge covering the in-service stage as well as 5 construction stages were established. The dynamic characteristics of the bridge associated with these stages were computed and applied in the analyses. Apart from the critical wind speeds for the onset of flutter, the dominant modes of vibration participating in the flutter vibration were also identified. The results indicate that the bridge will be stable against flutter at its in-service stage as well as during construction at wind speeds much higher than the verification wind speed of 95 m/s (1-minute mean).