• ETRI Journal
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• v.45 no.4
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• pp.581-593
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• 2023

This paper proposes four-ring slot resonator-based MIMO antennas of 75×150 mm² without and with CSRR structures in the sub-6-GHz range. These orthogonal-fed antennas have shown diverse characteristics with dual polarization. L-shaped parasitic structures have increased the isolation (i.e., >40 dB) in the single-element antenna over the band of 3.4 GHz-3.8 GHz. A set of three CSRR structures in the MIMO antenna reduced the coupling between antenna ports placed in an inline arrangement and enhanced the isolation from 12 dB to 20 dB and the diversity characteristics. The S-parameters of both MIMO antennas are measured and used to evaluate MIMO parameters like ECC, TARC, MEG, and channel capacity loss. The simulation results show the variations in the gain and directivity on exciting linear and dual polarizations. The diversity performance of the reported MIMO antennas is suitable for 5G applications.

• Journal of Digital Contents Society
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• v.6 no.2
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• pp.101-106
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• 2005

In this paper, performance evaluation of mobile access layer for multiple-input multiple-output (MIMO) MultiCarrier(MC)/CDMA 16 QAM system is considered to mitigate multiple access interference and enhance system channel capacity in Rayleigh wireless fading channel. Traditionally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, MIMO schemes is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA 16 QAM system is evaluated according to Eb/No, Mc, p. From the results, in order to improve the channel capacity, the signals at various elements must be uncorrelated. And if the paths are correlated due to inappropriate spacing or mutual coupling effects, the channel capacity of MIMO-MC/CDMA 16 QAM system becomes substantially smaller.

• ETRI Journal
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• v.39 no.5
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• pp.718-728
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• 2017

Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal-to-noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first-order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.

• Journal of Korean Society of Transportation
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• v.26 no.6
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• pp.17-27
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• 2008

Logistic activities of shippers contains only origin-destin commodity flow information, but also contract relationships, cash flows and distribution channels. Under the lack of understanding of physical distribution channels, most studies have focused on the social and psychological aspects between manufacturers and retailers (e.g., mutual trust, power, conflict, reciprocal commitment, and so on). This study reports empirical results of distribution channel choice drawn from 2001 Korean Commodity Flow Survey(CFS) conducted by Korean government. Based on the CFS data, four distribution channels are classified. This study scrutinized how various factors including mode, commodity and firms characteristics affect distribution channel choice, and reported the problems of 2001 CFS survey questionaires and future directions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1177-1189
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• 1994

This paper aims to develop the numerical model for prediction of the channel migration by analyzing of sediment and flow characteristics with patterns of channel in alluvial rivers. Flow in rivers constitutes to be the meandering or the braided form and rarely straight channel through morphologically stable patterns with mutual actions between the flowing water and bed materials. In order to develop the model for simulation of the channel migration, the channels are divided into two types with positive or negative sign by the direction of curvature radius of the centerline channel ($r_c$). That is, the single bend-channel consists of only one curvature of positive or negative sign and the multi-bend channel consists of two more curvatures of positive or negative sign, respectively. The model analyzes the sediment and flow characteristics under the influence of superelevation, spiral motion, irregularity in bed topography and depth-averaged velocity of channels. For reliability of this model, the single bend-channel and the multi bend channel are compared with experiment data in other models and the measured field data in the Keum-River, respectively. As a result, the both com parisians turn out to be excellent.

• Journal of Korean Society of Rural Planning
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• v.12 no.1 s.30
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• pp.67-74
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• 2006

This survey was carried out in order to obtain and apply the basic information on levels of raising skill, recognition of mutual infection between animal and human field of skill training, registration of animal pedigree, mating places, difficulties of raising, channel of marketing, and prospects of raising by socio-ecological status. Data were randomly gathered from 713 peoples, who composed of 398 men and 315 women, from March to August, 2005. As the results, questionnaires were analyzed that relatively 'the level of breeding skill is middle(43.9%)'. The average score for skill level is 1.81$\pm$0.79 when 4 points were used as a full mark. The recognition of mutual infection between human and animal is answered that 'many respondents don't know very well(62.6%)'. The questionnaire answered largely that 'the field of raising skill training is trimming and grooming(29.2%)'. The respondents recognized that 'The pedigree registration of pet is not essential(52.7%)'. The pet breeders answered that 'the mating for reproduction was conducted mainly in pet shops(34.3%)'. The breeders indicated mostly that 'the difficulties of raising were technical skills of raising(53.5%)'. The respondents answered that 'the deal of marketing of animal was mainly achieved through neighbors and close relatives(42.8%)'. The many questionnaires were recognized that 'breeders have a good prospect for the pet industry in the future(51.5%)'.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.5
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• pp.185-196
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• 2015

In a study of the existing Collaboration, U-I Collaboration linkage(LINK) has a width of the various channels through continuous mutual cooperation by the path-dependency. U-I Collaboration linkage(LINK) through the various channels is more powerful, whereas this increase trade-related barriers. In other words, It has been discussed in many literatures about the U-I Collaboration linkage(LINK). However, relatively a study on the factor of the barrier about U-I Collaboration linkage(LINK) is a minority. Given the importance of policies to establish an association of industry-university cooperation and support system, the lack of research on the obstacles to U-I Collaboration linkage(LINK) will be a serious obstacle for designing effective policies. This paper examines the existing literature about the width of mutual cooperation and the barrier of U-I Collaboration, analyze to lower the barrier of U-I cooperation through POB(Positive Organization Behavior) of university administration. In conclusion, we would like to suggest the policy implications.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.5
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• pp.71-78
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• 2009

In RFID system, the communicated data can be easily eavesdropped and tampered with by an attacker because the communication between the reader and the tag is performed in an insecure channel. Therefore, authentication is an important role in RFID applications for providing security and privacy. In 2006, Lee, Asano and Kim proposed an RFID mutual authentication protocol (the LAK protocol) which utilizes a hash function and synchronized secret information. However, Cao and Shen showed that the LAK protocol is vulnerable to replay attack, and therefore an adversary can impersonate the tag. This paper proposes a new simple two-round RFID mutual authentication (TRMA) protocol based on secure one-way hash function. As a result, the proposed TRMA protocol not only can prevent various attacks and but also provides communication efficiency since they mutually authenticate by performing two-round between RFID tag and RFID reader.

• Journal of Industrial Convergence
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• v.18 no.5
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• pp.23-29
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• 2020

The Internet of things (IoT) is the extension of Internet connectivity into various devices and everyday objects. Embedded with electronics, Internet connectivity and other forms of hardware. The IoT poses significant risk to the entire digital ecosystem. This is because so many of these devices are designed without a built-in security system to keep them from being hijacked by hackers. This paper proposed a mutual authentication protocol for IoT Devices using symmetric-key algorithm. The proposed protocol use symmetric key cryptographic algorithm to securely encrypt data on radio channel. In addition, the secret key used for encryption is random number of devices that improves security by using variable secret keys. The proposed protocol blocked attacker and enabled legal deives to communicate because only authenticated devices transmit data by a mutual authentication protocol. Finally, our scheme is safe for attacks such as eavesdropping attack, location tracking, replay attack, spoofing attack and denial of service attack and we confirmed the safety by attack scenario.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.5
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• pp.931-939
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• 2014

The Web or Mobile channel of previous Web access authentication system for a payment only provides the authentication of remote users, and does not provide the authentication between a user and a bank/financial institution. Therefore, this paper proposes the Transaction Certificate Mode(TCM) for a payment which can preserve the mutual authentication between a user and a bank/financial institution for Web-based payment systems. The proposed system has designed for wireless network instead of Secure Electronic Transaction (SET) designed for wired electronic transaction. In addition, this system with TCM is able to support an account-based transaction for wireless networks instead of a disadvantage of SET such as a card-based transaction for wired networks. Therefore, customers can check their balances without logging on their bank's web site again due to mutual authentication between a customer and his bank/financial institution.