• ETRI Journal
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• v.38 no.5
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• pp.1019-1029
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• 2016

The probability hypothesis density (PHD) filter is an effective means to track multiple targets in that it avoids explicit data associations between the measurements and targets. However, the target birth intensity as a prior is assumed to be known before tracking in a traditional target-tracking algorithm; otherwise, the performance of a conventional PHD filter will decline sharply. Aiming at this problem, a novel target birth intensity scheme and an improved measurement-driven scheme are incorporated into the PHD filter. The target birth intensity estimation scheme, composed of both PHD pre-filter technology and a target velocity extent method, is introduced to recursively estimate the target birth intensity by using the latest measurements at each time step. Second, based on the improved measurement-driven scheme, the measurement set at each time step is divided into the survival target measurement set, birth target measurement set, and clutter set, and meanwhile, the survival and birth target measurement sets are used to update the survival and birth targets, respectively. Lastly, a Gaussian mixture implementation of the PHD filter is presented under a linear Gaussian model assumption. The results of numerical experiments demonstrate that the proposed approach can achieve a better performance in tracking systems with an unknown newborn target intensity.

• Smart Structures and Systems
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• v.17 no.2
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• pp.167-194
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• 2016

This paper investigates the Synergetics based Damage Detection Method (SDDM) for frame structures by using surface-bonded PZT (Lead Zirconate Titanate) patches. After analyzing the mechanism of pattern recognition from Synergetics, the operating framework with cooperation-competition-update process of SDDM was proposed. First, the dynamic identification equation of structural conditions was established and the adjoint vector (AV) set of original vector (OV) set was obtained by Generalized Inverse Matrix (GIM).Then, the order parameter equation and its evolution process were deduced through the strict mathematics ratiocination. Moreover, in order to complete online structural condition update feature, the iterative update algorithm was presented. Subsequently, the pathway in which SDDM was realized through the modified Synergetic Neural Network (SNN) was introduced and its assessment indices were confirmed. Finally, the experimental platform with a two-story frame structure was set up. The performances of the proposed methodology were tested for damage identifications by loosening various screw nuts group scenarios. The experiments were conducted in different damage degrees, the disturbance environment and the noisy environment, respectively. The results show the feasibility of SDDM using piezoceramic sensors and actuators, and demonstrate a strong ability of anti-disturbance and anti-noise in frame structure applications. This proposed approach can be extended to the similar structures for damage identification.

• Smart Structures and Systems
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• v.25 no.6
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.17-23
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• 2010

The corporate R&D(Research and Development) has a primary role of new product development and its potential is the most crucial factor to estimate corporate future value. However, its systemic inadequacies and inefficiencies, the shorten product life-cycle to satisfy customer needs, the global operations by outsourcing strategy, and the reduction of product cost, are starting to expose to R&D business processes. The three-phased execution strategy for R&D innovation is introduced to establish master plan for new R&D model. From information technology point of view, PLM(Product Life-cycle Management) is one of the business total solutions in product development area. It is not a system, but the strategic business approach that collaboratively manage the product from beginning stage to end of life in all business areas PLM functions and capabilities are usually used as references to re-design new R&D process. BPA(Business Process Assessment) and 5DP(Design Parameters) in PI6sigma developed by Samsung SDS Consulting division are introduced to establish R&D master plan and re-design process respectively. This research provides a case study for R&D process innovation. How process assessment and PMM(Process Maturity Model) can be applied in business processes, and also it explains process re-design by 5DP method.

• Journal of Digital Convergence
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• v.15 no.2
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• pp.251-262
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• 2017

This study distinguishes between factors that affect mental health of college students, establishes an effective approach to integrating model building, mental health promotion, and development of nursing intervention based on the Bronfenbrenner's ecological system theory. The study method investigate the causal relationship between the factors. The SPSS 20.0 program was used for general characteristics and mental health related characteristics. The fitness of the model was verified and the Amos 20.0 program was used for hypothesis verification. In the study, the fit index of the model was $x^2=614.90$ (p = .000), Q value = 3.5, GFI = .88, AGFI = .84, NFI = .92, NNFI = .94, CFI = .02, and RMSEA = .08, respectively. The results showed that stress was the most influential on mental health, and that stress coping strategies, self - esteem and parenting attitude affect mental health. In order to improve the mental health of college students, intervention should be carried out to develop nursing interventions to improve stress management, self - esteem, and coping with stress.

• Smart Structures and Systems
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• v.17 no.1
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• pp.149-165
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• 2016

Floods have been known to be one of the main causes of bridge collapse. Contrary to earthquakes, flood events tend to occur repeatedly and more frequently in rainfall areas; flood-induced damage and collapse account for a significant portion of disasters in many countries. Nevertheless, in contrast to extensive research on the seismic fragility analysis for civil infrastructure, relatively little attention has been devoted to the flood-related fragility. The present study proposes a novel methodology for deriving flood fragility curves for bridges. Fragility curves are generally derived by means of structural reliability analysis, and structural failure modes are defined as excessive demands of the displacement ductility of a bridge under increased water pressure resulting from debris accumulation and structural deterioration, which are known to be the primary causes of bridge failures during flood events. Since these bridge failure modes need to be analyzed through sophisticated structural analysis, flood fragility curve derivation that would require repeated finite element analyses may take a long time. To calculate the probability of flood-induced failure of bridges efficiently, in the proposed framework, the first order reliability method (FORM) is employed for reducing the required number of finite element analyses. In addition, two software packages specialized for reliability analysis and finite element analysis, FERUM (Finite Element Reliability Using MATLAB) and ABAQUS, are coupled so that they can exchange their inputs and outputs during structural reliability analysis, and a Python-based interface for FERUM and ABAQUS is newly developed to effectively coordinate the fragility analysis. The proposed framework of flood fragility analysis is applied to an actual reinforced concrete bridge in South Korea to demonstrate the detailed procedure of the approach.

• Informatization Policy
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• v.17 no.3
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• pp.36-56
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• 2010

The number of studies on e-government has increased rapidly in South Korea while the government has implemented world-class e-government. However, there has been little effort to assess the achievements and limitations of e-government studies up to the present. This article analyzes 146 research papers from 43 academic journals by using the meta-analysis method. Our analysis focuses on the papers' perspectives and topics, methodologies and methods, and use of theories. Comparisons to similar foreign studies are also conducted. Our finding shows that there have been substantial improvements and practical contributions of e-government research, mainly in Public Administration and Information Systems literature. Some recommendations are suggested on ways to strengthen e-government research: a multi-disciplinary approach, the rigor and diversity of research methods, theory building, salience, and plasticity.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.19-34
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• 2005

The difficulties in implementing of image processing algorithms are a major reason for the lack of research into algorithm comparison. This fact makes an image processing research with difficult. We conclude that it is important to represent algorithms in form of reusable code. Since current image processing systems do not fulfill all requirements we must pose on reusable implementations, we propose to solve the reuse problem by applying generic programming. We define two dimensional iterators, which mediate between image processing algorithms and their underlying data structures, so that the same algorithm implementation can be applied to any number of different image formats. The elegance and efficiency of this approach is illustrated by a number of useful examples and demonstrated by porting in existing image processing algorithm IDE(Integrated Development Environment).

• Journal of the Korea Convergence Society
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• v.11 no.5
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• pp.9-17
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• 2020

Human activity recognition(HAR) using smartphones is a hot research topic in computational intelligence. Smartphones are equipped with a variety of sensors. Fusing the data of these sensors could enable applications to recognize a large number of activities. However, these devices have fewer resources because of the limited number of sensors available, and feature selection and classification methods are required to achieve optimal performance and efficient feature extraction. This paper proposes a smartphone-based HAR scheme according to these requirements. The proposed method in this paper extracts time-domain features from acceleration sensors, gyro sensors, and barometer sensors, and recognizes activities with high accuracy by applying KDA and SVM. This approach selects the most relevant feature of each sensor for each activity. Our comparison results shows that the proposed system outperforms previous smartphone-based HAR systems.

• Journal of Korea Game Society
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• v.7 no.2
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• pp.21-32
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• 2007

It is significant to simulate scattering of light within media for realistic image synthesis; however, this requires costly computation. This paper introduces a practical image-space approximation technique for interactive subsurface scattering. We use a general two-pass approach, which creates transmitted irradiance samples onto shadow maps and computes illumination using the shadow maps. We estimate single scattering efficiently using a method similar to common shadow mapping with adaptive deterministic sampling. A hierarchical technique is applied to evaluate multiple scattering, based on a diffusion theory. We further accelerate rendering speed by tabulating complex functions and utilizing level of detail. We demonstrate that our technique produces high-quality images of animated scenes with blurred shadow at hundreds frames per second on graphics hardware. It can be integrated into existing interactive systems easily.