• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.643-650
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• 2014

Recently, the wireless communication applications are studied in various environment by the development of short range communication system like wireless sensor networks. This paper presents the analysis of localization schemes for ship application using received signal strength. The localization schemes using received signal strength from wireless networks are classified under two methods, which are Range based method and Range free method. Range based methods estimate the location with least square estimation based on estimated distance using path-loss model. Range free methods estimated the location with the information of anchor nodes linked to target. Simulation results show the appropriate localization scheme for each cabin environments based on the empirical path-loss model in warship's internal space.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2985-2991
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• 2013

Train radio system has been constructed in the second stage of Kyung-bu high speed railway adopting TETRA(Terrestial trunk radio) standard at 851MHz frequency band. The base stations of the train radio system should be located along railway track to ensure seamless communication between train and wayside taking the path loss of train radio propagation into consideration. This paper provides a quantitative analysis of the path loss characteristics based on the measurement results of the train radio propagation along the high speed railway. The free space propagation model and Okumura-Hata model are generally used for base station design, but they predicted 10dB lower or 20dB higher than the measured path loss. Linear regression of the field measured data by applying the log-distance model shows path loss exponent is in the 2.8-3.2 range, which can be used to predict the path loss of the train radio propagation.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.186-189
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• 2010

Reflection(R($\omega$)), transmission(T($\omega$)) and loss(L($\omega$)) characteristics of multi-layer metamaterials are investigated experimentally in free space with the incident EM waves perpendicular to the substrate plane. The sample is made of split-ring resonators(SRRs) and wires which are the typical model of metamaterials. The R($\omega$) and T($\omega$) of multi-layer metamaterials have been calculated from the measured S-parameters. In this paper, we got the impedance-matched result according to the curves of R($\omega$), meanwhile the T($\omega$) decreased with increasing number of layers. At last, we attained the result that the L($\omega$) gets to nearly 98% around 8 GHz, with R($\omega$)=T($\omega$)=0. The design presented in this paper achieves experimented loss near unity.

• Archives of Craniofacial Surgery
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• v.10 no.1
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• pp.40-43
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• 2009

Purpose: Extensive midface defect following total maxillectomy with orbital exenteration and cheek skin resection should be three dimensionally reconstructed with a large flap that have a sufficient volume of tissue and multiple skin islands. We describe our transverse rectus abdominis myocutaneous(TRAM) free flap with three skin islands which was successfully used in this situation. Methods: A 58-year-old man was performed enbloc total maxillectomy including orbital contents and wide cheek skin because of invasive maxillary squamous cell carcinoma. He was immediately reconstructed with TRAM flap that was designed not vertical but transverse fashion for providing sufficient skin area. Also, deepithelialization procedure making for multiple skin islands was done in flap insetting period when appropriate modification according to the intraoperative situation was possible. Dead space was completely obliterated by bulky muscular tissue, and three skin islands were used for lining of lateral nasal wall, palatal surface, and cheek skin restoration. Results: Postoperative course was satisfying. Maintaining of proper ipsilateral nasal airway, loss of rhinolalia and oronasal regurgitation of food particles, and restoration of cheek contour were successfully obtained. Conclusion: We report clinical experience of threedimensional reconstruction using free TRAM flap after total maxillectomy with orbital exenteration.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.162-168
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• 2006

Understanding of propagation characteristics is very important for the wireless communication system design and wireless communication service construction. In this paper, propagation characteristics is measured and analyzed at 2.45Ghz frequency band under curved subway tunnel environment. We constituted channel measurement system with sliding correlation and five different kind of antennas. The purpose of five different type of antennas is to compare propagation characteristics according to beam shape of antennas. The path loss under tunnel environment is average $4.38^{\sim}14.41dB$ lower than free space and circular polarization antenna marked smallest path loss. Also, path loss is smallest when the receiver antenna located outside of tunnel in th curved section. 90% of delay components of all antennas measured within 20ns and directional antenna has more wide coherence bandwidth than omni-directional antenna. According to measured result, when we consider path loss and delay characteristics, circular polarization antenna is most suitable under tunnel environment.

• Archives of Reconstructive Microsurgery
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• v.21 no.1
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• pp.56-60
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• 2012

Purpose: Thumb reconstruction plays most important role in hand injuries because total loss of a thumb constitutes about 40% disability in the hand. The reconstruction can be accomplished by pollicization, free toe-to-thumb transfer, wrap around procedure and lengthening extraction. However, we sometimes need consecutive or double free flaps in the reconstruction of mutilating hand injuries. Methods: We reconstructed a mutilating hand injury in a 54-years old man. Because of severe crushing injury of right thumb and index fingers, we reconstructed a thumb with pollicization using nearly amputated middle finger. Although it survived completely, the adjacent soft tissues which had been covered by fillet flap from the space past was necrosed on 1 month. We debrided the necrotic tissues and covered it with anteromedial thigh perforator free flap consecutively because he had an anatomical variation in branches of lateral femoral circumflex artery. Results: He had an uneventful postoperative course without any complication such as infection, dehiscence and flap necrosis. Three months later, he had undergone tenolysis and defatting procedure of flap site. He recovered the some amount of grip function and was happy with the result. Conclusion: In severe hand trauma including thumb amputation, thumb reconstruction using pollicization and perforator free flap could be an alternative option. It provides minimal donor site morbidity and an acceptable functional result.

• Korean Institute of Interior Design Journal
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• v.24 no.3
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• pp.186-196
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• 2015

This research comprehended the fundamental cause of elderly nursing home residents' negative feelings of loneliness, depression, fear, and loss of self-usefulness as existential issue, since they already went through loss, death of loved ones, geriatric disease and disability. The purpose of this research is to explore how existentialism and existential psychotherapy theory of Irvin D. Yalom can be applied to nursing home environment design, and to suggest design directions. Based on his framework of human's ultimate interest, death, freedom followed by responsibility, isolation, and meaninglessness, interior design suggestions and applicable spaces were presented. Four cases from Australia, Denmark, Japan and Korea were analyzed according to design suggestions to grasp the current situation and to draw further proposition. The conclusions are as follows. (1)Environment should support nursing home residents to resolve existential issues. (2)Death is the least supported issue on all of the cases. Environmental elements that can induce residents to think and discuss on death, hospice program and space for memorial service is necessary. (3)Regarding to freedom, the environment should support resident's disability to maintain independence as much as possible and residents autonomy and decision should be respected. Single/double rooms, motorized bed, free and safe usage of kitchen and garden are necessary. (4)For isolation, Space and time for meditation should be provided. (5)To find meaning of life, environment should support residents in both physical and cognitive aspect so that they can contribute to others. Space for hobby is necessary for continued creativity and self-realization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.64-71
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• 2004

The object of this study is to design the Radar Absorbing Structures (RAS) having sandwich structures in the X-band ($8.2{\sim}12.4GHz$) frequencies. Glass fabric/epoxy composites containing conductive carbon blacks and carbon fabric/epoxy composites were used for the face sheets. Polyurethane(PU) foams containing multi-walled carbon nanotube (MWNT) were used for the core. Their permittivities in the X-band were measured using the transmission line technique. The reflection loss characteristics for multi-layered sandwich structures were calculated using the theory of transmission and reflection in a multi-layered medium. Three kinds of specimens were fabricated and their reflection losses in the X-band were measured using the free space technique. Experimental results were in good agreements with simulated ones in 10dB absorbing bandwidth.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.97.1-97.1
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• 2014

We clarify the dynamics connecting a solar flare and a coronal mass ejection (CME) based on the results of a magnetohydrodynamic (MHD) simulation starting from a nonlinear force-free field (NLFFF) in Inoue et al. 2014. In previous studies, many authors proposed numerous candidates for triggering processes of a solar flare and the associated CME. Among them, the tether-cutting reconnection or the torus instability has been supported by recent simulations and observations. On the other hand, our MHD simulation in accordance with more realistic situations show that highly twisted field lines are first produced through a tether-cutting reconnection between the twisted field lines in the NLFFF, and then the newly formed, strongly twisted field erupts away from the solar surface because of a loss of equilibrium. This dynamics corresponds to the onset of a solar flare. Furthermore we have found that the strongly twisted erupting field reconnect with the weakly twisted ambient field during the eruption, creating a large flux tube, and then it rises over a critical height of the torus instability to trigger a CME. From these results, we conclude that the coupled process of tether-cutting reconnection and torus instability is important in the flare-CME relationship.

• Current Optics and Photonics
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• v.8 no.4
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• pp.382-390
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• 2024

Laser propagation through atmospheric disturbances is vital for applications such as laser optical communication, satellite laser ranging (SLR), laser guide stars (LGS) for adaptive optics (AO), and laser energy transmission systems. Beam degradation, including energy loss and pointing errors caused by atmospheric turbulence, requires thorough numerical analysis. This paper investigates the impact of laser beam parameters on ground-to-space laser propagation up to an altitude of 100 km using vertical atmospheric disturbance profiles from the Geochang SLR Observatory in South Korea. The analysis is confined to 100 km since sodium LGS forms at this altitude, and beyond this point, beam propagation can be considered free space due to the absence of optical disturbances. Focusing on a 100-watt class laser, this study examines parameters such as laser wavelengths, beam size (diameter), beam jitter, and beam quality (M²). Findings reveal that jitter, with an influence exceeding 70%, is the most critical parameter for long-exposure radius and pointing error. Conversely, M², with an influence over 45%, is most significant for short-exposure radius and scintillation.