• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.528-535
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• 2012

This paper proposes silence drop first(SDF) active buffer management algorithm to increase the voice capacity when silence suppression is used. This algorithm finds and drops silence packet rather than voice packet in the queue for resolving buffer overflow of queue. Simulations with voice codec of G.729A and G.711 are performed. By using proposed SDF algorithm, the voice capacity is increased by 84.21% with G.729A and 38.46% with G.711. Further more, SDF algorithm reduces the required link capacity and loosens the silence packet inter-arrival time limit to provide target voice quality compared with that of conventional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.371-380
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• 2013

D2D (Device-to-Device) communication on an underlying cellular infrastructure which exploits the same spectrum has several advantages such as increased resource utilization and improved cellular coverage. However, D2D communication system needs to cope with ICI (Inter-Cell Interference) and interference between cellular and D2D links. As a result, macro UEs (User Equipments), especially those located near cell edge, will suffer from serious link performance degradation. We propose a novel interference avoidance mechanism assisted by SRN (Shared Relay Node) in this paper. SRN not only performs data re-transmission as a usual Type II relay but also has several features newly defined to avoid interference between cellular and D2D links. In particular, we suggest resource allocation methods based on the SRN for effective interference avoidance, and evaluate their performance through computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.853-866
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• 2008

In this paper, a multi-hop relaying transmission scheme is analyzed regarding its feasibility and potentiality in the IEEE 802.22-based cognitive radio (CR) environment. Shortly, basic design issues are addressed such as relay station (RS) deployment and a frame structure of physical channel to escape inter-hop interference. This paper mainly develops a radio resource management scheme based on spectrum sensing results aggregated from CR secondary nodes and improves the opportunistic spectrum sharing efficiency. In particular, a decision rule about a channel availability is made using a distributed sensing method. Subsequently, spectrum allocation and routing path decision procedures are proposed to establish a link from source to destination with a hop-by-hop manner. Simulation results show that the proposed multi-hop relaying scheme is substantially profitable in CR environments if the number of hops and RS deployment are designed in such a way that the spectrum sharing gain is larger than spectrum division loss which is inherently induced in multi-hop relaying systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.121-127
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• 2011

This paper presents an autonomous formation flight algorithm for micro aerial vehicles (MAVs) and its flight test results. Since MAVs have severe limits on the payload and flight time, formation of MAVs can help alleviate the mission load of each MAV by sharing the tasks or coverage areas. The proposed formation guidance law is designed using nonlinear dynamic inversion method based on 'Leader-Follower' formation geometric relationship. The sensing of other vehicles in a formation is achieved by sharing the vehicles' states using a high-speed radio data link. the designed formation law was simulated with flight data of MAV to verify its robustness against sensor noises. A series of test flights were performed to validate the proposed formation guidance law. The test result shows that the proposed formation flight algorithm with inter-communication is feasible and yields satisfactory results.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.137-142
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• 2005

Since wireless communication cost is relatively expensive, the mobile games using cellular phones or PDAs are mostly played after being downloaded unlike more updated types of phone-to-phone or online games. In particular, the upbringing games, in which garners foster virtual companion animals or vegetables as their avata, have been spotlighted. It is essential to supply variety of items for upbringing avatas. However, due to diverse tastes for avatas and limited storage of mobile terminals, game manias must download their desired items from homepages. In addition, game developers must inform users through SMS messages whenever a new item is created. To do so, they must link WEB server and WAP server to Call Back URL or ARS. This paper proposed a linkage method suitable for JAVA-based mobile phone operating system. The proposed method will consequently increase life cycle of a game and reinforce profitability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4002-4014
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• 2015

ITU-R M.1842-1, as a well-known specification dedicated to maritime mobile applications, has standardized wireless transmission protocols according to the particular characteristics of a maritime communications scenario. A time division multiple access (TDMA) frame structure, along with modulation schemes to achieve a high data rate, has been described clearly in ITU-R M.1842-1. However, several specification items are still under "to be decided" status, which brings ambiguity to research works. In addition, the current version of ITU-R M.1842-1 is focused mainly on maritime transmissions in open-sea areas, where the cyclic prefix (CP) is set to zero and only 16-QAM is used in the multi-carrier (MC) system. System performance might be dramatically degraded in coastline areas due to the inter-symbol interference (ISI) caused by selective fading. This is because there is a higher probability that the signal will be reflected by obstacles in coastline areas. In this paper, we introduce the transmission resource block (TRB) dedicated to ITU-R M.1842-1 for a ship ad-hoc network (SANET), where the pilot pattern of TRB is based on the terrestrial trunked radio (TETRA). After that, we evaluated SANET performance under the maritime channel model in a coastline area. In order to avoid noise amplification and to overcome the ISI caused by selective fading, several strategies are suggested and compared in the channel estimation and equalization procedures, where the link-level simulation results finally validate our proposals.

• Journal of the Economic Geographical Society of Korea
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• v.22 no.3
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• pp.237-245
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• 2019

The aim of this article is to introduce articles of the special issue on 'Revitalization Conditions on Crisis on Industrial Regions: Experience from Europe and the Republic of Korea, and to explore policy alternatives to crisis on industrial regions on the basis of policy diagnoses and prescriptions. In the existing research, diagnoses of such Korean regions are quantitatively focused upon industry, employment, plant, consumption, investment, real estate, and labour market, and are qualitatively based upon external environment and functional, structural and spatial characteristics. Prescriptions of such regions emphasize the establishment of a law and an institutional fix, financial supports, jobs' creation, industrial diversification, the intensification of urban foundation throughout the urban revitalizaion. In the policy development for these regions, it is required to link the industrial sector to social, educational, political and welfare sectors, and furthermore the collaboration of inter- and intra-ministry and the active participation of provincial and local governments are needed.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.11-21
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• 2021

In the last few years, there is growing interest in the field of simultaneous equation estimation in finance due to the endogeneity problem caused by measurement errors, simultaneity, or omitted variables. This study aims to discuss the endogeneity problem in corporate financing decisions and investigate the interrelationship of financial decision-making such as investment decision, dividend decision, and external financing decision in Pakistan Stock Exchange (PSX) using two-stage least squares (2SLS) and generalized method of moment (GMM) estimation. The Bruech-Pagan test shows that the data has no heteroskedasticity issue and 2SLS is a better approach in the context of this study as compared to the GMM approach, and internal instruments are also sufficiently strong and valid. The three financial decision-making attributes are not jointly determined, and the dividend is influenced by one-sided investment. In the emerging stock market context, external financing and investment are not inter-related and did not affect each other. The question of whether the simultaneous equation estimation can be useful in the context of the emerging stock markets and newly-growing firms remains unanswered. The inclusive evidence shows that the theoretical link in the emerging stock market is difficult to prove like in developed stock markets.

• English & American cultural studies
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• v.10 no.2
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• pp.149-207
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• 2010

Written simultaneously with Prometheus Unbound, Shelley's "Julian & Maddalo" is a masterwork of dramatic poiesis, of doubling embedded in its couplets, dialogic debate on human nature and contrasted symbolic emblems. The emblems mirror each other and are themselves sites of generative paradox: the "heaven illumined" but "dreary tower" of the Maniac and the glorious sunsets on the "ever-shifting sand" of the Lido, a wasteland that is a place of self discovery but also of "abandonment" and barren mingling figured, inter alia, in its "amphibious weeds," a trope of the poem's personae. This essay also explores the poem's dramatic structure and various rhetorical devices, beginning with the Preface, a threshold of complex identity disguise that Shelley uses for veiled self-presentation, as in "Alastor," mirroring and literary references replete with nuanced ironies. I focus mainly on the complex figures of liminality Shelley uses to develop his own thoughts (as well as his ongoing debates with Byron) about man's potential for growth in thought, insight and empathy, in political reform and interpersonal and individual healing. Advancing Shelley's most optimistic ideas, Julian, escorted by Maddalo observes the Maniac, -- a living ruin whose pained eloquence reveals the link of eros to poiesis and the limits of the latter's ability to 'transform a world.' The Maniac is the core of muse-work (remembering, thinking and song) and Shelley presents him as its emblem. He also is prefigured in and reflects the quintessentially liminal Lido with its "barren embrace" of sea and land. Yet it is less the Maniac's feeling that his grief is "charactered in vain…on this unfeeling leaf" than Julian's rationales for leaving the site of pain that point to Shelley's final comment on poetry's transformative limits. As the primary haploids of the drama's meiosis re-combine and two of them, Maddalo and the maniac fall away, an analogy I briefly develop and embedded in the erotic dynamics of poiesis, Shelley suggests, as he did at the beginning of his poetic lyricism in "Alastor" and at its end in "the Triumph of Life"that images mislead and delude; that "the deep truth is imageless" and redemption is not in but beyond figuration.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.30.1-30.1
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• 2020

The ASKAP-EMU survey is a deep wide-field radio continuum survey designed to cover the entire southern sky and a significant fraction of the northern sky up to +30°. Here, we report a discovery of a radio relic in the merging cluster SPT-CL J2023-5535 at z=0.23 from the ASKAP-EMU pilot 300 square degree survey (800-1088 MHz). The deep high-resolution data reveal a ~2 Mpc-scale radio halo elongated in the east-west direction, coincident with the intracluster gas. The radio relic is located at the western edge of this radio halo stretched ~0.5 Mpc in the north-south orientation. The integrated spectral index of the radio relic within the narrow bandwidth is α1088MHz800MHz = -0.76 ± 0.06. Our weak-lensing analysis shows that the system is massive (M200 = 1.04 ± 0.36 × 1015M⊙) and composed of at least three subclusters. We suggest a scenario, wherein the radio features arise from the collision between the eastern and middle subclusters. Furthermore, the direct link between the local AGN and the relic along with the discontinuities in X-ray observation hint us that we are looking at the site of re-acceleration.