• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.1
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• pp.50-55
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• 2002

$Nd_2O_3$0.2~0.5 wt.% doped $LiNbO_3$single crystals were grown by the Czochralski method. The ZnO doping by 2~8 mole% can improve the resistance of optical damage. In this study, Nd : LiNbO$_3$ single crystals with the periodical domain structure were obtained by CZ method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.120-128
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• 2011

Recently, safety diagnosis of the existing structures has been emerged as important issue. In particular, systematical and precise safety diagnostics for steel structures for power substation, have been required. Steel structures for power substation are under the periodical impact loads from operations of gas insulated switchgear. These loading condition accelerates damage and aging of structure. The objective of this research is to evaluate damage of structure under periodical impact loads. To evaluate the integrity of structures as organizing mathematical models including the dynamic characteristics of structures, Frequency Domain Decomposition method was choiced and an algorism was proposed. For verifying this methods and algorism, a mathematical model is composed of the development of a variety of reverse analysis and a signal processing technology reflecting physical damage of structures. A series of analysis and test results indicatge that proposed method has a confidence for applying a filed test. Therefore, it is expected to be able to take advantage of system identification to detect damage for the maintenance and management of steel structures under periodical impact loads such as power substation.

• Interaction and multiscale mechanics
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• v.6 no.1
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• pp.15-29
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• 2013

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.677-684
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• 2010

Backlashes of gears provide gears for good lubrication and for removal of the interference between teeth by the wear and manufacturing errors. The backlash is the strong nonlinear factor to gears. This study deals with nonlinear modeling of helical gears with backlash. Excitation of helical gears comes from torque variation, the tooth surface error, and the periodical change of mesh stiffness. To study the effect of torque fluctuation, equation of motion for the single degree of freedom torsional model of helical gears with the periodical change of mesh stiffness and the backlash was derived. The Newmark beta method and the Newton-Raphson method were used to obtain the nonlinear behaviors of mesh forces of helical gears. All excitation frequencies initially caused the tooth separation and single-sided impacts of the gear pair and eventually led to the normal tooth contact. However, some special excitation frequencies caused the single-sided impacts in the entire time as well as the initial time. Damping increase reduced the duration of single-sided impacts, and the backlash increase caused those in the entire time domain.

• Architectural research
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• v.18 no.1
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• pp.31-38
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• 2016

The surface design in architecture plays a role as an indicator that symbolizes cultures and styles, in accordance with the course of history and the standards of the time. The surface design that determines the facade of an architectural structure allows us to have a more clear understanding about the functions, programs and structures, as well as the periodical concept of the architects than any other components of the architecture. The purpose of this paper was to examine how architectural surface designs were realized, using commonly-used materials. This study provides meaningful implications, in that it suggests common features in terms of design methodologies (between architecture and non-architecture fields), and presented new possibilities for contemporary architectural surface designs through the classification of building system methods depending on fabric properties, and through the case study analysis of architectural surface designs; in addition, the results of this study could be utilized as basic data for future studies on the possibility of the expression of surface designs across a broader domain.

• Journal of Korea Technology Innovation Society
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• v.1 no.3
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• pp.436-450
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• 1998

This paper is about strategies for developing information and telecommunications standardization experts(ITSEs). For an analysis of current status of ITSEs or development of strategies for education and utilization of ITSEs, it is necessary to classify the types and roles of ITSEs. The classification of ITSEs can be made standardization technology field, characteristics of expert field, and activity domain. It is necessary to remind the ever growing importance of development and utilization of ITSEs. Furthrmore, More importanct is to set right direction and strategies with valid alternatives to enhance the importance. Correct direction setting, right problem-mindedness, long-term perspective, periodical evaluations are crucial to the policy of further development and utilization of ITSEs.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1732-1737
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• 2004

This paper proposes Internet-based checking technique for machine-tools with variant CNC (Computerized Numerical Controller). According to the architecture of CNC, CNC is classified into two types such as CAC (Closed Architecture Controller) which is conventional CNC, and OAC (Open Architecture Controller) which is a recently introduced PC-based controller. CAC has a closed architecture and it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement an application programs in CNC domain. Therefore, an additionally special module is required for Internet-based application such as remote checking. In this case, web I/O embedded module can be efficiently applied for Internet-based checking. The module is directly attached to TCP/IP network for communication. In order to obtain the monitoring data of CNC machines, the I/O signals of the module are assigned to PLC (Programmable Logic Controller) input and output (I/O) signals within CNC domain. On the other hand, OAC has a PC-based open architecture and an additional module is not necessary for the connection with external site. Because of this, a simple DAU is just used for signal sensing and data acquisition without additional communication modules. For Internet-based remote checking of machine-tools with OAC, a user-defined daemon and application programs are implemented as the form of internal function within the PC-based controller. Internet communication is performed between the daemon program in CNC domain and web script programs in external server. Checking points defined in this research are classified into two categories such as structured point and operational point. The formal includes the vibration of bearing, temperature of spindle unit and another periodical management. And the latter includes oil checking, clamp locking/unlocking and machining on/off status.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.115-126
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• 2023

Due to the fluctuating random and periodical nature of renewable energy generation power quality disturbances occurred more frequently in power generation transformation transmission and distribution. Various power quality disturbances may lead to equipment damage or even power outages. Therefore it is essential to detect and classify different power quality disturbances in real time automatically. The traditional PQD identification method consists of three steps: feature extraction feature selection and classification. However, the handcrafted features are imprecise in the feature selection stage, resulting in low classification accuracy. This paper proposes a deep neural architecture based on Convolution Neural Network and Long Short Term Memory combining the time and frequency domain features to recognize 16 types of Power Quality signals. The frequency-domain data were obtained from the Fast Fourier Transform which could efficiently extract the frequency-domain features. The performance in synthetic data and real 6kV power system data indicate that our proposed method generalizes well compared with other deep learning methods.

• Korean Journal of Psychosomatic Medicine
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• v.12 no.1
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• pp.3-14
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• 2004

In this article, the effects of stress on central nerve system and heart function and the concept of heart rate variability were reviewed. HRV(Heart Rate Variability), the periodical change of the heart rate, is indicated larger in the healthier because they respond flexibly to various sorts of facts influencing on HR. HRV analysis is largely composed of the time domain analysis and the frequency analysis. In the former the flexibility of heart function is analysed, while in the latter autonomic nerve function is examined, which is the degree of sympathetic and parasympathetic nerve activity and the state of balance. Furthermore, existence or nonexistence of disease and/or level of stress can be estimated by measuring the variability and normality of heart rate, and balance of autonomic nerve system, and through HRV biofeedback the symptoms of anxiety disorder or asthma can be reduced.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.259-259
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• 2010

Periodically polarity inverted (PPI) ZnO structures on (0001) Al2O3 substrates are demonstrated by plasmas assisted molecular beam epitaxy. The patterning and re-growth methods are used to realize the PPI ZnO by employing the polarity controlling method. For the in-situ polarity controlling of ZnO films, Cr-compound buffer layers are used.[1, 2] The region with the CrN intermediate layer and the region with the Cr2O3 and Al2O3 substrate were used to grow the Zn- and O-polar ZnO films, respectively. The growth behaviors with anisotropic properties of PPI ZnO heterostructures are investigated. The periodical polarity inversion is evaluated by contrast images of piezo-response microscopy. Structural and optical interface properties of PPI ZnO are investigated by the transmission electron microcopy (TEM) and micro photoluminescence ($\mu$-PL). The inversion domain boundaries (IDBs) between the Zn and the O-polar ZnO regions were clearly observed by TEM. Moreover, the investigation of spatially resolved local photoluminescence characteristics of PPI ZnO revealed stronger excitonic emission at the interfacial region with the IDBs compared to the Zn-polar or the O-polar ZnO region. The possible mechanisms will be discussed with the consideration of the atomic configuration, carrier life time, and geometrical effects. The successful realization of PPI structures with nanometer scale period indicates the possibility for the application to the photonic band-gap structures or waveguide fabrication. The details of application and results will be discussed.