• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.651-659
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• 2014

In this paper, we consider a two way relay network for ship-to-ship communications in a fleet, where two communicating ships exchange the information with the help of a multi-antenna relay ship. For the network, we propose a rate-aware three-phase analog network coding to improve the reliability of the information exchange with asymmetric rates. The proposed scheme allows low-complex implementation of the relay without channel estimation by generating an improved analog network coded signal with the orthogonally received signals from two ships by using only the received signal power at each antenna. In addition, the proposed scheme reduces outages in the data exchange at asymmetric rates by adopting a rate-aware relay power allocation, which is confirmed by evaluating the outage performance via simulation.

• Journal of IKEEE
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• v.19 no.3
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• pp.357-365
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• 2015

Recently, embedded systems such as aircraft and automobilie, are developed as modular architecture instead of federated architecture because of SWaP(Size, Weight and Power) issues. In addition, partition operating system that support multiple logical node based on partition concept were recently appeared. Distributed recovery block is fault tolerance design scheme that applicable to mission critical real-time system to support real-time take over via real-time synchronization between participated nodes. Because of real-time synchronization, single-core based computer is not suitable for partition based distributed recovery block design scheme. Multi-core and AMP(Asymmetric Multi-Processing) based partition architecture is required to apply distributed recovery block design scheme. In this paper, we proposed design scheme of distributed recovery block on the multi-core based supervised-AMP architecture partition operating system. This paper implements flight control simulator for avionics to check feasibility of our design scheme.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.73-79
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• 2008

We propose a novel metal-waveguide structure for sustaining long-range surface-plasmon-polaritons (LRSPP). The LRSPP waveguides are composed basically of two asymmetric metal layers: a very thin, finite-width metal strip on top of a metal slab with a dielectric gap in between them. Mode cut-off of LRSPPs excited on the double-metal waveguides is characterized by consistently investigating their dispersion relations and mode profiles. We also confirm experimentally the existence of low-loss, well-confined LRSPP modes by measuring far-field outputs emerging from an edge of the asymmetric double-metal waveguides. In the experiment, we have fabricated several types of SPP waveguide devices including straight lines, S-bend, and Y-branch consisting of gold strips (20 nm-thick, $5{\mu}m$-wide). Overall propagation loss of the proposed double-metal waveguides is quite comparable to that of single metal-strip waveguides, in addition the mode sizes can be tuned by increasing the core-insulator gap between the metal layers to get a higher coupling efficiency with a single-mode fiber in telecom wavelength. The proposed LRSPP waveguides may open up realization of SPP-waveguide sensors or nonlinear SPP-devices by replacing the core-insulator with a bio-fluid or a nonlinear medium.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.778-785
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• 2010

The folded monopole antenna for applying mobile communications equipment and wireless devices is presented in this paper. By using the coplanar waveguide feed the operating bandwidth has improved. In addition, each individual resonant elements has occurred different capacitance through asymmetrical left and right ground planes; therefore, the bandwidth has kept and the impedance matching has stabilized. By measurement results, the impedance bandwidth under VSWR< 2.5:1 are $824{\sim}890$ MHz and the $1,500{\sim}2,170$ MHz, also radiation patterns has omni-directional characteristics. The maximum gains of the proposed antenna are 5.52, 0.64, 3.00, 0.94 and 1.85 dBi at 850, 1,575, 1,790, 1,930 and 2,050 MHz respectively. The proposed antenna will be adapted to the internal antenna of the mobile communication devices.

• International Area Studies Review
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• v.18 no.3
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• pp.67-88
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• 2014

The Chinese stock market has increasingly strengthened its market power on other stock markets due to rapid growth of its economy. In this context, this study investigated return spillover effect as well as asymmetric volatility spillover effect using a VAR-Bivariate EGARCH model among stock markets(China, US, Japan, Korea). Furthermore, we conjectured the impact of 2008 global financial crisis on the spillover effect of the Chinese stock market. In our empirical results, the Chinese stock market has a weak return spillover effect to other markets(US, Japan, Korea), but after the global financial crisis, its return spillover effect becomes stronger among other stock markets. In addition, the Chinese stock market have strengthened its asymmetric volatility spillover effect on other stock markets after the Global financial crisis. As a result, the Chinese stock market has an strong influence on other stock markets.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.419-426
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• 2018

Recently, in an effort to reduce the energy efficiency design index (EEDI), studies on energy saving devices (ESDs) have been conducted. In this study, we designed a post-device suitable for a KRISO container ship (KCS) using computational fluid dynamics (CFD). In order to increase the efficiency of the post-device, a twisted rudder was used, which has a proven performance (showing a 1.34% reduction in DHP compared to the bare hull at 24 knots) in previous research at Pusan National University. In addition, an increase in efficiency was expected by the use of a rudder bulb, including the discontinuous section of the twisted rudder and a divergent propeller cap to prevent the contraction of the wake. The optimization criterion was the case where the delivery power was the least compared with the bare hull. We analyzed the cause of the efficiency increase through an analysis of the self-propulsion factor. The case study for optimization was divided into 4 types (1. clearance of the bulb and cap, 2. shape of the bulb, 3. size of the bulb and cap, and 4. asymmetric bulb). Finally, with a clearance of 50 mm from the ship, a spherical bulb with the cap having an angle of $5^{\circ}$, and an asymmetric rudder bulb with a bulb diameter of 1.2HH/1.4H (horizontal/vertical) showed a 2.05% reduction in DHP compared to the bare hull at 24 knots. We will fabricate a post-device that will be optimized in the future and verify the performance of the post-device through model tests.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.31-42
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• 2005

We consider a network storage model whose administrator can not be fully trusted. In this model, we assume that all data stored are encrypted for data confidentiality and one owner distributes the decryption key for each time period to users. In this paper, we propose three privilege management schemes. In the first scheme, called Temporal Privilege Management (TPM), we use a symmetric encryption based on one-way function chains for key encapsulation. In the second scheme, called Asymmetric Temporal Privilege Management (ATPM), anyone can encrypt the data using the public key of owner, but only privileged users can decrypt the encrypted data. Finally, we present a scheme to restrict writers' privilege using ID-based signatures in ATPM. In our schemes, the privilege managements are based on the time and the addition of users is efficient. Specially, applying TPM and ATPM, we can solve the back-issue problem.

• Journal of The Korean Astronomical Society
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• v.55 no.5
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• pp.149-172
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• 2022

We present a new method which constructs an Hɪ super-profile of a galaxy which is based on profile decomposition analysis. The decomposed velocity profiles of an Hɪ data cube with an optimal number of Gaussian components are co-added after being aligned in velocity with respect to their centroid velocities. This is compared to the previous approach where no prior profile decomposition is made for the velocity profiles being stacked. The S/N improved super-profile is useful for deriving the galaxy's global Hɪ properties like velocity dispersion and mass from observations which do not provide sufficient surface brightness sensitivity for the galaxy. As a practical test, we apply our new method to 64 high-resolution Hɪ data cubes of nearby galaxies in the local Universe which are taken from THINGS and LITTLE THINGS. In addition, we also construct two additional Hɪ super-profiles of the sample galaxies using symmetric and all velocity profiles of the cubes whose centroid velocities are determined from Hermite h3 polynomial fitting, respectively. We find that the Hɪ super-profiles constructed using the new method have narrower cores and broader wings in shape than the other two super-profiles. This is mainly due to the effect of either asymmetric velocity profiles' central velocity bias or the removal of asymmetric velocity profiles in the previous methods on the resulting Hɪ super-profiles. We discuss how the shapes (𝜎_n/𝜎_b, A_n/A_b, and A_n/A_tot) of the new Hɪ super-profiles which are measured from a double Gaussian fit are correlated with star formation rates of the sample galaxies and are compared with those of the other two super-profiles.

• Journal of Korea Trade
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• v.25 no.3
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• pp.1-20
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• 2021

Purpose - The purpose of this paper is to examine the welfare effects of standards harmonization between technologically asymmetric countries, and to determine optimal harmonization strategies for a country with mid-level technological advancement. Design/methodology - Following Salop's circular city model (Salop, 1979), this study constructs a simple, horizontally-differentiated oligopoly model in which three firms and three countries exist. Each country adopts different compatibility standards and each firm incurs conversion costs for foreign market access due to differences in standards. The conversion costs are related to technology; standards harmonization removes these costs between participating countries. The paper considers three cases: i) no harmonization; ii) harmonization with the more technologically-advanced country and iii) harmonization with the less technologically-advanced country. Findings - The paper first considers a scenario in which all three firms occupy some share of the market in each country. It shows that standards harmonization with both the technologically moreor less-advanced country always increases consumer surplus and social welfare. In addition, the producer surplus will increase if the harmonization partner has a higher technology level, whereas it may decrease if the partner has a lower technology level. It also shows that if most domestic export goods are in sectors with conversion costs above a certain level, harmonizing standards with a technologically more-advanced country should be prioritized. Such strategies, moreover, should be emphasized when there exists a large technology gap among countries. Lastly, the paper considers another scenario, in which harmonization leads to the foreclosure of the non-member firm from the member countries' markets. It shows that harmonization improves the social welfare of a mid-level technology country regardless of its partner's technology. It also shows that the country should prioritize harmonization with the technologically less-advanced country. Originality/value - Though some of the existing studies consider the welfare effects of harmonization, their main assumption is that firms have the same conversion technology. Since complying with standards often requires substantial technological advancement and technical expertise, harmonization of compatibility standards between countries with gaps in technological ability carries different implications. This paper investigates the welfare effects of this harmonization and determines an optimal harmonization strategy while considering technological asymmetry among countries in standards compliance.

• Journal of Internet of Things and Convergence
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• v.8 no.1
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• pp.79-85
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• 2022

Internet of Things (IoT) connects devices with various platforms, computing power, and functions. Due to the diversity of networks and the ubiquity of IoT devices, demands for security and privacy are increasing. Therefore, cryptographic mechanisms must be strong enough to meet these increased requirements, while at the same time effective enough to be implemented in devices with long-range specifications. In this paper, we present the performance and memory limitations of modern cryptographic primitives and schemes for different types of devices that can be used in IoT. In addition, detailed performance evaluation of the performance of the most commonly used encryption algorithms in low-spec devices frequently used in IoT networks is performed. To provide data protection, the binary ring uses encryption asymmetric fully homomorphic encryption and symmetric encryption AES 128-bit. As a result of the experiment, it can be seen that the IoT device had sufficient performance to implement a symmetric encryption, but the performance deteriorated in the asymmetric encryption implementation.