• 디지털융복합연구
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• 제12권4호
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• pp.133-143
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• 2014

본 연구는 거래비용요소가 경영성과에 미치는 영향을 검증한 것이다. 연구결과, 첫째, 불확실성은 재무적 성과와 비재무적성과에 직접적으로 영향을 미치는 것으로 나타났지만, 자산특유성과 기회주의는 경영성과에 직접적인 영향이 없는 것으로 분석되었다. 둘째, 협력관계 지속요인에 직접적으로 영향을 미치는 변수는 자산특유성과 불확실성으로 나타났으나. 기회주의는 직접적인 영향이 없는 것으로 나타났다. 셋째, 관계만족도에 직접적으로 영향을 미치는 변수는 자산특유성과 기회주의로 나타났으며, 불확실성과의 관계는 없는 것으로 분석됐다. 넷째, 협력관계 지속요인과 관계만족도는 재무적 성과와 비재무성과에 각각 직접적으로 영향을 미치는 것으로 나타났다. 요약하면, 거래비용요소가 협력관계 지속요인과 관계만족도라는 매개변수를 통하여 경영성과에 영향을 미치고 있음을 발견하였다.

• Journal of Microbiology and Biotechnology
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• 제24권6호
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• pp.795-802
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• 2014

The aim of this study was to determine the effects of temperature and supplementation with skim milk powder (SMP) on the microbial and proteolytic properties during the storage of cottage cheese. Cottage cheese was manufactured using skim milk with 2% SMP and without SMP as the control, and then stored at $5^{\circ}C$ or $12^{\circ}C$ during 28 days. The chemical composition of the cottage cheese and the survival of the cheese microbiota containing starter lactic acid bacteria (SLAB) and non-starter culture lactic acid bacteria (NSLAB) were evaluated. In addition, changes in the concentration of lactose and lactic acid were analyzed, and proteolysis was evaluated through the measurement of acid soluble nitrogen (ASN) and non-protein nitrogen (NPN), as well as electrophoresis profile analysis. The counts of SLAB and NSLAB increased through the addition of SMP and with a higher storage temperature ($12^{\circ}C$), which coincided with the results of the lactose decrease and lactic acid production. Collaborating with these microbial changes, of the end of storage for 28 days, the level of ASN in samples at $12^{\circ}C$ was higher than those at $5^{\circ}C$. The NPN content was also progressively increased in all samples stored at $12^{\circ}C$. Taken together, the rate of SLAB and NSLAB proliferation during storage at $12^{\circ}C$ was higher than at $5^{\circ}C$, and consequently it led to increased proteolysis in the cottage cheese during storage. However, it was relatively less affected by SMP fortification. These findings indicated that the storage temperature is the important factor for the quality of commercial cottage cheese.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5898-5916
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• 2018

In this paper, the downlink performance of multi-cell distributed antenna systems (DAS) with a single user in each cell is investigated. Assuming the channel state information is available at the transmitter, four transmission modes are formulated as combinations of remote antenna units (RAUs) selection and cooperative transmission, namely, non-cooperative transmission without RAU selection (NCT), cooperative transmission without RAU selection (CT), non-cooperative transmission with RAU selection (NCT_RAUS), and cooperative transmission with RAU selection (CT_RAUS). By using probability theory, the cumulative distribution function (CDF) of a user's signal to interference plus noise ratio (SINR) and the system ergodic capacity under the above four modes are determined, and their closed-form expressions are obtained. Furthermore, the system energy efficiency (EE) is studied by introducing a realistic power consumption model of DAS. An expression for determining EE is formulated, and the closed-form tradeoff relationship between spectral efficiency (SE) and EE is derived as well. Simulation results demonstrate their consistency with the theoretical analysis and reveal the factors constraining system EE, which provide a scientific basis for future design and optimization of DAS.

• Journal of Communications and Networks
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• 제10권2호
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• pp.204-212
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• 2008

We study the routing problem in all-wireless networks based on cooperative transmissions. We model the minimum-energy cooperative path (MECP) problem and prove that this problem is NP-complete. We hence design an approximation algorithm called cooperative shortest path (CSP) algorithm that uses Dijkstra's algorithm as the basic building block and utilizes cooperative transmissions in the relaxation procedure. Compared with traditional non-cooperative shortest path algorithms, the CSP algorithm can achieve a higher energy saving and better balanced energy consumption among network nodes, especially when the network is in large scale. The nice features lead to a unique, scalable routing scheme that changes the high network density from the curse of congestion to the blessing of cooperative transmissions.

• Journal of information and communication convergence engineering
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• 제16권1호
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• pp.17-22
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• 2018

In massive multiple-input multiple-output (MIMO) systems, linear channel estimation algorithms are widely applied owing to their simple structures. However, they may cause pilot contamination, which affects the subsequent data detection performance. Therefore, herein, for an uplink multicell massive multiuser MIMO system, we consider using an alternating projection (AP) for channel estimation to eliminate the effect of pilot contamination and improve the performance of data detection in terms of the bit error rates as well. Even though the AP is nonlinear, it iteratively searches the best solution in only one dimension, and the computational complexity is thus modest. We have analyzed the mean square error with respect to the signal-to-interference ratios for both the cooperative and non-cooperative multicell scenarios. From the simulation results, we observed that the channel estimation results via the AP benefit the following signal detection more than that via the least squares for both the cooperative and non-cooperative multicell scenarios.

• 기술혁신연구
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• 제5권1호
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• pp.1-14
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• 1997

Firms prefer in some specific conditions cooperative R&D to non-cooperative for developing technology. Previous studies on the conditions show firms want to choose cost-sharing type of cooperative R&D (the CS-RJV) rather than non-cooperative one when target technology is either 'relatively easy' or 'relatively difficult', and to join multiple-research or pararell-research type of cooperation (the PR-PJV) than to compete each other if technology is only 'relatively easy'. However, by introducing technological leakage as well as difficulty of technology. it is shown that this seemingly contrasted phenomenon almost disappears ; the PR-RJV can be also preferred by firms even is case of 'relatively difficult' technology only if there exists some extent of a technological leakage.

• 한국학교수학회논문집
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• 제1권1호
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• pp.197-205
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• 1998

This study aims to examine how cooperative teaming of small ability level groups influences the enhancement of their scholastic achievement in mathematics. The conclusions are as follows; 1. The students which participate in cooperative learning in small ability level groups demonstrate academic improvement over those that participate in non-cooperative learning groups. 2. In particular, this method is more effective for high-level classes, than for middle or low-level students. 3. The learners' perception, interest and attitude towards mathematics has not changed through their placement in small ability groups involved in cooperative activities.

• Journal of Information Processing Systems
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• 제13권3호
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• pp.630-642
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• 2017

In this paper, we propose the opportunistic non-orthogonal multiple access (NOMA)-based cooperative relaying system (CRS) with channel state information (CSI) available at the source, where CSI for the source-to-destination and source-to-relay links is used for opportunistic transmission. Using the CSI, for opportunistic transmission, the source instantaneously chooses between the direct transmission and the cooperative NOMA transmission. We provide an asymptotic expression for the average achievable rate of the opportunistic NOMA-based CRS under Rayleigh fading channels. We verify the asymptotic analysis through Monte Carlo simulations, and compare the average achievable rates of the opportunistic NOMA-based CRS and the conventional one for various channel powers and power allocation coefficients used for NOMA.

• 한국컴퓨터정보학회논문지
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• 제23권3호
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• pp.25-31
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• 2018

In this paper, we consider the game theoretic approach to investigate the transmit power optimization problem where D2D users share the uplink of the cellular system. Especially, we formulate the transmit power optimization problem as a non cooperative power control game. In the user wide sense, each user may try to select its transmit power level so as to maximize its utility in a selfish way. In the system wide, the transmit power levels of all users eventually converge to the unique point, called Nash Equilibrium. We first formulate the transmit power optimization problem as a non cooperative power control game. Next, we examine the existence of Nash Equilibrium. Finally, we present the numerical example that shows the convergence to the unique transmit power level.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2281-2301
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• 2014

In wireless ad hoc networks the nodes focus on achieving the maximum SINR for efficient data transmission. In order to achieve maximum SINR the nodes culminate in exhausting the battery power for successful transmissions. This in turn affects the successful transmission of the other nodes as the maximum transmission power opted by each node serves as a source of interference for the other nodes in the network. This paper models the choice of power for each node as a non cooperative game where the throughput of the network with respect to the consumption of power is formulated as a utility function. We propose an adaptive pricing scheme that encourages the nodes to use minimum transmission power to achieve target SINR at the Nash equilibrium and improve their net utility in multiuser scenario.