• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.95-102
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• 2004

For the simultaneous measurement of strain and damage signal, a fiber Bragg grating sensor system with a dual demodulator was proposed. One demodulator using a tunable Fabry-Perot filter can measure low-frequency signal such as strain and the other demodulator using a passive Mach-Zehnder interferometer can detect high-frequency signal such as damage signal or impact signal. Using a proposed fiber Bragg grating sensor system, both the strain and damage signal of a cross-ply laminated composite beam under tensile loading were simultaneously measured. Analysis of the strain and damage signals detected by single fiber Bragg grating sensor showed that sudden strain shifts were induced due to transverse crack propagation in the 90 degree layer of composite beam and vibration with a maximum frequency of several hundreds of kilohertz was generated.

• Smart Structures and Systems
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• v.25 no.1
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• pp.111-122
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• 2020

Researchers up to date have introduced several Structural Health Monitoring (SHM) techniques with varying advantages and drawbacks for each. Satellite positioning systems (GPS, GLONASS and GALILEO) based techniques proved to be promising, especially for high natural period structures. Particularly, the GPS has proved sufficient performance and reasonable accuracy in tracking real time dynamic displacements of flexible structures independent of atmospheric conditions, temperature variations and visibility of the monitored object. Tall structures are particularly sensitive to oscillations produced by different sources of dynamic actions; such as typhoons. Wind forces induce in the structure both longitudinal and perpendicular displacements with respect to the wind direction, resulting in torsional effects, which are usually more complex to be detected. To efficiently track the horizontal rotations of the in-plane sections of such flexible structures, two main issues have to be considered: a suitable sensor topology (i.e., location, installation, and combination of sensors), and the methodology used to process the data recorded by sensors. This paper reports the contributions of the measurements recorded from dual frequency GPS receivers and uni-axial accelerometers in a full-scale experimental campaign. The Canton tower in Guangzhou-China is the case study of this research, which is instrumented with a long-term structural health monitoring system deploying both accelerometers and GPS receivers. The elaboration of combining the obtained rather long records provided by these two types of sensors in detecting the torsional behavior of the tower under ambient vibration condition and during strong wind events is discussed in this paper. Results confirmed the reliability of GPS receivers in obtaining the dynamic characteristics of the system, and its ability to capture the torsional response of the tower when used alone or when they are combined with accelerometers integrated data.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.1-6
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• 2018

The torque ripple that is generated by the irregularity of magnetic flux density on the BLDC motor in a satellite actuator degrades the satellite attitude control performance. In this paper, the performance analysis of permanent magnet configurations (shape, arrangement, and air gap) is simulated by the Finite Element Method (FEM) to find the appropriate combination of the configuration. The configuration is chosen by comparing between rectangular and arc-shaped permanent magnets and single-arrangement and dual-arrangement magnets. The performance is verified by a prototype.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.69-75
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• 2013

To increase the efficiency of the photovoltaic, almost photovoltaic appliances are controlled by Maximum Power Point Tracking(MPPT). Existing most of the PV MPPT techniques have used power which multiplies sensed output current and voltage of the solar cell. However, these algorithms are unnecessarily complicated and too expensive for small and compact system. The other hand, the proposed MPPT technique is only one sensing of the MPPT converter's output current, so there is no need to insert another sensors of battery side. Therefore, this algorithm is simpler compared to the traditional approach and is suitable for low power solar system. Further, the novel proper charge/discharge algorithm for the battery with PV MPPT is developed. In this algorithm, there is CC battery charge mode and load discharge mode of the PV cell & battery dual. Also we design current control to regulate allowable current during the battery charging. The proposed algorithm will be applicable to battery included solar cell applications like solar lantern and solar remote control car. Finally, the proposed method has been verified with computer simulation.

• Journal of the Korea Society of Computer and Information
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• v.15 no.7
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• pp.67-74
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• 2010

TIn this paper, it is designed the polarization selective antenna for UHF RFID system. The proposed antenna is consist of microstrip patch antenna with dual feeding and two SPDT switches and a SP4T switch and 3dB hybrid coupler. Through control of voltage of switches, the proposed reader antenna can select horizontally linear polarization, vertically linear polarization, left-hand circular polarization (LHCP) and right hand circular polarization (RHCP). The proposed reader antenna satisfied 2:1 VSWR at 902MHz~928MHz. and it has under 3dB AR(axial ratio). Peak gain of antenna is 7.71dBi, 7.55dBi with linear polarization and 7.31dBic, 7.81dBic with circular polarization at x-y plane. Also Axial ratio of antenna is 2.01~2.83dB and 2.02~2.60dB respectively. It is satisfied 3dB axial ratio.

• Journal of architectural history
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• v.17 no.5
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• pp.71-94
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• 2008

This study examines the examples and changes of wooden member terms in Yeonggeon-euigwe(營建儀軌) in the era of Joseon Dynasty. As a result of examining examples, about 240 wood member terms were found on the basis of phonetic value and examples different from today's term use were also confirmed. Wood member terms were derived in variety and synonym and different style, that is, coexistence or transition of several notations as the term indicating the same member was found. Derivation of detail terms has the characteristic increasing on the basis of morpheme and formation of different notation followed Chinese notation or was caused by complex coinage features like a coined word of Korea by the meaning of a word and borrowed character notation borrowing sound and it is also related to the specificity of that time which had dual language system. The typical examples without different style for long were pillar, rafter, door and window. Examples with active generation and selection of different styles included beam, capital and bracket-system terms. Different styles were caused by the combination of several notations including borrowed character in the process of Chinese character notation borrowing sound, Korean unique character emphasizing and limiting combination of 木 (wood) with side of character and Chinese. Period showing remarkable change of example notation was the compilation of ${\ll}$the Hwa-Sung-Sung-Euk-Eui-Gue${\gg}$ 華城城役儀軌. ${\ll}$the Hwa-Sung-Sung-Euk-Eui-Gue${\gg}$ is the representative type uigwe made by printed type not by handicraft. Printing by type accompanies unification of the shape of a character necessarily and it was considered that it resulted in the unification of character of different style, the number of strokes and minute difference of strokes, and it was interpreted that common use of intentional notation with the unification of the shape of a character was achieved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.628-636
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• 2014

This paper describes the design and analysis of five-element planar array antenna of an anti-jamming satellite navigation system. We propose a design of multi-layer patch antenna for Global Positioning System(GPS) $L_1/L_2$ dual bands. The proposed antenna has two ports feeding network with a hybrid chip coupler for a broad bandwidth with Right-Handed Circular Polarization(RHCP). The measurement results show the bore-sight gains of 1.10 dBic($L_1$) and 0.37 dBic($L_2$) for the center element. The bore-sight gains of an edge element are 0.99 dBic($L_1$) and -0.57 dBic($L_2$). At a fixed elevation angle of $30^{\circ}$, antennas show average gains of -2.08 dBic ($L_1$) and -5.33 dBic($L_2$) for the center element, and average gains of -0.40 dBic($L_1$) and -2.09 dBic($L_2$) for the edge elements. The results demonstrate that the proposed array antenna is suitable for anti-jamming applications.

• The Korean Journal of Air & Space Law and Policy
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• v.3
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• pp.233-258
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• 1991

This paper examines current developing status of space law as defined in terms of its unique principle that "the utilization of outer space for all mankind's interest". As commercialization of space activities has brought about heated debate on its legitimacy with respect to that principle, space law has come to witness a dual situation. One is the realization of that principle in establishing commercial space activities system where all mankind's interest is respected through the non-discriminatory distribution mode of space benefit. In satellite telecommunication system, the INTELSAT Organization assures its public service policy while protecting itself against a competition from separate systems. For remote sensing, commercialization of LANDSAT Systems promoted since 1984 seems not to affect present non-discriminatory distribution of data and information obtained. On the other hand, active participation of private entity aiming at commercial profit enables national government to manage more effective control and supervision of those activities with a view to promoting national interests. Also, newly developed private rules and regulations are emerging in business relations about commercial space activities. Extended capacity of national government assuring its national interest in production and distribution of international resources that is outer space, and regulation of space activities by newly developed rules and customs provoke a concern about a identity problem of space law. The best way to summarize this perspective might consist in saying that non space law regulations, which are not assumed as aiming at the promotion of all mankind's interest, are confirming their role about space related activities. For those reasous, we are now facing a developing status of space law as developments of commercial space activities continues.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.632-636
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• 2006

It is needed to use the beam scanning to control the cell coverage of the base station considering operation conditions, season, time period, radiation character and mobility of customers and vehicles for varied wireless communication service and quality improvement. This paper proposes a mobile antenna system which can obtain the characteristics of the beam scanning by controlling the directivity depending on the operation condition. Radiation block is made of 2 sub-array of $1\times3$ patched antennas for ITS of 5.8GHZ bandwidth with the gain of 13dBi, and of 2 sub-array of single patched antenna for WiBro of 2.3GHZ bandwidth with the gain of 12dBi. RF module is made of a switch, an amplifier, a PAD, a 3-Bit phase shifter, and a power divider. The system is able to control the beam tilting with electronic methode by using 3-bit phase shifter$(45^{\circ},\;90^{\circ},\;180^{\circ})$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.197-198
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• 2017

The purpose of this study is to investigate the problems of the VR simulator industry represented by the 4th industrial revolution and to examine measures for industrial promotion. For this purpose, we consider the VR simulator regulation and examine the problems. Since the VR simulator has the features of existing arcade games and amusement facilities, it should be classified as game or inspected with amusement facilities depending on the viewpoint. This can be a dual regulation, and before the VR simulator industry starts, there is a risk that the industry itself can be damaged by existing legal limitations. For this purpose, it is necessary to provide a unique legal system for VR simulator and it is necessary to examine the contents to be included in such laws and systems. It is expected that the legal system of VR simulator will lead to promotion of new industry.