• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.807-813
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• 2015

In the present study, an interferometer system, which integrates the laser sensitivity control technique based on the theory of electronic speckle pattern interferometry, one of non-contact non-destructive analysis methods, was developed. This interferometry system receives an image from CCD cameras for each reference and object, and compares the photosensitivity of the object and reference images from imagification. For the purpose of this study, the photosensitivity of object and reference light is measured with power meters, and the amount of light was controlled with an ND filter with a reference light port matching photosensitivity. Using the plate specimen as the object, 0.6, 0.9, 1.2, and $1.5{\mu}m$ of out-plane deformation was made, and images were compared according to the difference in photosensitivity. After analysis, larger object deformations showed larger numbers of stripe patterns. Images became clearer and data error was reduced when the photosensitivity of object and reference light matched.

• Smart Structures and Systems
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• v.10 no.3
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• pp.229-251
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• 2012

Guided waves have shown a great potential for structural health monitoring (SHM) applications. In contrast to traditional non-destructive testing (NDT) methodologies, a key element of SHM approaches is the high process of automation. The monitoring system should decide autonomously whether the host structure is intact or not. A basic requirement for the realization of such a system is that the sensors are permanently installed on the host structure. Thus, baseline measurements become available that can be used for diagnostic purposes, i.e., damage detection, localization, etc. This paper contributes to guided wave-based inspection in anisotropic materials for SHM purposes. Therefore, computational strategies are described for both, the solution of the complex equations for wave propagation analysis in composite materials based on exact elasticity theory and the popular global matrix method, as well as the underlying equations of two active damage localization algorithms for anisotropic structures. The result of the global matrix method is an angular and frequency dependent wave velocity characteristic that is used subsequently in the localization procedures. Numerical simulations and experimental investigations through time-delay measurements are carried out in order to validate the proposed theoretical model. An exemplary case study including the calculation of dispersion curves and damage localization is conducted on an exemplary unidirectional composite structure where the ultrasonic signals processed in the localization step are simulated with the spectral element method. The proposed study demonstrates the capabilities of the proposed algorithms for accurate damage localization in anisotropic structures.

• Advances in Computational Design
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• v.5 no.4
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• pp.363-380
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• 2020

In this paper, a cylindrical shell is immersed in a non-viscous fluid using first order shell theory of Sander. These equations are partial differential equations which are solved by approximate technique. Robust and efficient techniques are favored to get precise results. Employment of the Rayleigh-Ritz procedure gives birth to the shell frequency equation. Use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. Throughout the computation, simply supported edge condition is used. Expressions for modal displacement functions, the three unknown functions are supposed in such way that the axial, circumferential and time variables are separated by the product method. Comparison is made for empty and fluid-filled cylindrical shell with circumferential wave number, length- and height-radius ratios, it is found that the fluid-filled frequencies are lower than that of without fluid. To generate the fundamental natural frequencies and for better accuracy and effectiveness, the computer software MATLAB is used.

• The Journal of Korean Medicine
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• v.32 no.1
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• pp.56-66
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• 2011

Background: This was a study to analyze Sanghanron through network theory, as the first attempt to construct network models for systems biomedicine in traditional Korean medicine. For this purpose, we investigated the network structure with priority given to two-node connections between symptoms and herbs of Taeyangbyung compilation in Sanghanron. Purpose: We had three goals in carrying out this study. First, to establish the minimum clinical grouping data sets for symptoms and herbs of Taeyangbyung compilation in Sanghanron. Second, to make index files for the obtained data sets. Third, to generate a network structure for systems biomedicine in this part, and analyze its relationship. Methods: Using MS office Excel and Netminer software, we constructed the minimum clinical grouping data sets and the network for systems biomedicine about symptoms and herbs of Taeyangbyung compilation in Sanghanron, and analyzed its relationship. Results: We established the minimum clinical grouping data sets for symptoms and herbs of Taeyangbyung compilation in Sanghanron, using MS Excel. We constructed a network to structurize our database through two-node connections of Netminer program, and analyzed its relationships. Conclusions: Further research on network model for systems biomedicine between symptoms and herbs for three Yang and three Um(Taeyang, Soyang, Yangmyung, Taeum, Soum, Gualum) disease compilation is necessary.

• International Journal of Oral Biology
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• v.43 no.2
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• pp.101-111
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• 2018

Understanding the classification of malocclusion is a crucial issue in Orthodontics. It can also help us to diagnose, treat, and understand malocclusion to establish a standard for definite class of patients. Principal component analysis (PCA) and k-means algorithms have been emerging as data analytic methods for cephalometric measurements, due to their intuitive concepts and application potentials. This study analyzed the macro- and meso-scale classification structure and feature basis vectors of 1020 (415 male, 605 female; mean age, 25 years) orthodontic patients using statistical preprocessing, PCA, random matrix theory (RMT) and k-means algorithms. RMT results show that 7 principal components (PCs) are significant standard in the extraction of features. Using k-means algorithms, 3 and 6 clusters were identified and the axes of PC1~3 were determined to be significant for patient classification. Macro-scale classification denotes skeletal Class I, II, III and PC1 means anteroposterior discrepancy of the maxilla and mandible and mandibular position. PC2 and PC3 means vertical pattern and maxillary position respectively; they played significant roles in the meso-scale classification. In conclusion, the typical patient profile (TPP) of each class showed that the data-based classification corresponds with the clinical classification of orthodontic patients. This data-based study can provide insight into the development of new diagnostic classifications.

• Korean Journal of Oriental Medicine
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• v.2 no.1
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• pp.84-103
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• 1996

The physiological signals measured by Oriental Medicine instruments have been analyzed quantitatively in the view of the rule of promoting and counteracting relation of five evolutive phases theory. We tried to reduce the physiological signals measured by EAV(Elec-tro-Acupuncture according to Voll) and IR thermography to the representation of five evelutive phases. The EAV index and local skin temperature on acupuncture points of each phases measured and normalized so that the total value of five phases became unity. We assumed that the normalized EAV index and local skin temperature mean the deficiency or excess of Qi for each phases. The state of Qi distribution for each phases were approximately agree with the diagnostic pattern of O. M. doctor. Taking account of the Qi distribution state of·or the five evolutive phases, we performed a proper needle insertion on acupuncture points to induce the distinct change of Qi for each phases. We compared the measured results with the predictions of Qi variation by the rule of pro- moting and counteracting relation over the five evolutive phases. For all cases, the variation of Qi in the own phase on which a needle insertion was performed were exactly same to the theoretical prediction and partial agreement was shown for the other four phases. The same analysis was carried to the results of skin temperature measurements at accupoints. We found that the local skin temperature at accupoints of each phases shelved a finite change by the needle insertion and the behavior- of its change were strongly correlated to the rule of promoting and counteracting relation of five evolutive phases.

• Journal of the Korean Society for information Management
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• v.34 no.2
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• pp.47-80
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• 2017

The purpose of this study is to develop an adoptive model of institutional repositories (IRs) by identifying the key factors affecting adoptive intention of IRs and explaining the relations among these factors. Through a survey of 270 researchers and 12 in-depth interviews in the field of physics, mathematics, and life science in Korea, performance expectancy, perceived risks, socio-organizational influence, and individual characteristics were found to have substantial influences on the adoptive intention of IRs. Among the key factors, individual characteristics showed the greatest effect on the adoptive intention of IRs, followed by performance expectancy and other socio-organizational influences except for the perceived risks. Strategies to enhance the adoptive intention of IRs based on analyses of the results were suggested, in terms of the reformation of research assessment system at the national level, strengthening of role of the operational institution, and the need for voluntary scientists-participating service.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.2-2
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• 2011

Single-walled carbon nanotubes (SWNTs) have been considered as a promising candidate for nextgeneration electronics due to its extraordinary electrical properties associated with one-dimensional structure. Since diversity in electronic structure depends on geometrical features, the major concern has been focused on obtaining the diameter, chirality, and density controlled SWNTs. Despite huge efforts, the controlled synthesis of SWNTs has not been achieved. There have been various approaches to synthesize controlled SWNTs by preparation of homogeneously sized catalyst because the SWNTs diameter highly depends on catalyst nanoparticles size. In this study, geometrically controlled SWNTs were synthesized using designed catalytic layers: (a) morphologically modified Al2O3 supporting layer (Fe/Al2O3/Si), (b) Mo capping layer (Mo/Fe/Al/Si), and (c) heat-driven diffusion and subsequent evaporation process of Fe catalytic nanoparticles (Al2O3/Fe/Al2O3/Si). These results clearly revealed that (a) the grain diameter and RMS roughness of Al2O3 supporting layer play a key role as a diffusion barrier for obtaining Fe nanoparticles with a uniform and small size, (b) a density and diameter of SWNTs can be simultaneously controlled by adjusting a thickness of Mo capping layer on Fe catalytic layer, and (c) SWNTs diameter was successfully controlled within a few A scale even with its fine distribution. This precise control results in bandgap manipulation of the semiconducting SWNTs, determined by direct comparison of Raman spectra and theory of extended tight binding Kataura plot. We suggest that these results provide a simple and possible way for the direct growth of diameter, density, and bandgap controlled SWNTs by precise controlling the formation of catalytic films, which will be in demand for future electronic applications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.504-521
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• 2016

Recently, energy harvesting technology has been integrated into wireless sensor networks to ameliorate the nodes' energy limitation problem. In theory, the wireless sensor node equipped with an energy harvesting module can work permanently until hardware failures happen. However, due to the change of power supply, the traditional hierarchical network routing protocol can not be effectively adopted in energy harvesting wireless sensor networks. In this paper, we improve the Low-Energy Adaptive Clustering Hierarchy (LEACH) protocol to make it suitable for the energy harvesting wireless sensor networks. Specifically, the cluster heads are selected according to the estimation of nodes' harvested energy and consumed energy. Preference is given to the nodes with high harvested energy while taking the energy consumption rate into account. The utilization of harvested energy is mathematically formulated as a max-min optimization problem which maximizes the minimum energy conservation of each node. We have proved that maximizing the minimum energy conservation is an NP-hard problem theoretically. Thus, a polynomial time algorithm has been proposed to derive the near-optimal performance. Extensive simulation results show that our proposed routing scheme outperforms previous works in terms of energy conservation and balanced distribution.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.45.1-45.1
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• 2016

Spatially rotating magnetic fields have been observed in the solar wind and in the Earth's magnetopause as well as in reversed field pinch (RFP) devices. Such field configurations have a similarity with extended current layers having a spatially varying plasma pressure instead of the spatially varying guide field. It is thus expected that magnetic reconnection may take place in a rotating magnetic field no less than in an extended current layer. We have investigated the spontaneous evolution of a collisionless plasma system embedding a rotating magnetic field with a two-and-a-half-dimensional electromagnetic particle-in-cell (PIC) simulation. In magnetohydrodynamics, magnetic flux can be decreased by diffusion in O-lines. In kinetic physics, however, an asymmetry of the velocity distribution function can generate new magnetic flux near O- and X-lines, hence a dynamo effect. We have found that a magnetic-flux-reducing diffusion phase and a magnetic-flux-increasing dynamo phase are alternating with a certain period. The temperature of the system also varies with the same period, showing a similarity to sawtooth oscillations in tokamaks. We have shown that a modified theory of sawtooth oscillations can explain the periodic behavior observed in the simulation. A strong guide field distorts the current layer as was observed in laboratory experiments. This distortion is smoothed out as magnetic islands fade away by the O-line diffusion, but is soon strengthened by the growth of magnetic islands. These processes are all repeating with a fixed period. Our results suggest that a rotating magnetic field configuration continuously undergoes deformation and relaxation in a short time-scale although it might look rather steady in a long-term view.