• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4291-4310
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• 2015

This paper investigates the traffic offloading over unlicensed bands for two-tier multi-mode small cell networks. We formulate this problem as a Stackelberg game and apply a hierarchical learning framework to jointly maximize the utilities of both macro base station (MBS) and small base stations (SBSs). During the learning process, the MBS behaves as a leader and the SBSs are followers. A pricing mechanism is adopt by MBS and the price information is broadcasted to all SBSs by MBS firstly, then each SBS competes with other SBSs and takes its best response strategies to appropriately allocate the traffic load in licensed and unlicensed band in the sequel, taking the traffic flow payment charged by MBS into consideration. Then, we present a hierarchical Q-learning algorithm (HQL) to discover the Stackelberg equilibrium. Additionally, if some extra information can be obtained via feedback, we propose an improved hierarchical Q-learning algorithm (IHQL) to speed up the SBSs' learning process. Last but not the least, the convergence performance of the proposed two algorithms is analyzed. Numerical experiments are presented to validate the proposed schemes and show the effectiveness.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.459-466
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• 2002

In Korea, a need of automatic dairy farm management system has been increased to lower production cost and to strengthen international competition. However, the present management system was mostly relied on foreign technologies and caused some problems in post management and after-sales services. Therefore, though there is a problem of price and quality at present, domestic technologies of the management system should be developed for the long run. This study was conducted to develop an electronic identification unit for an automatic dairy farm management system. The developed system was consisted of a tag, a reader, a switching circuit, and a personal computer. The tag attachable to each individual cow was developed to transmit individual radio frequency(RF) code into the air with modulation of ASK(amplitude shift keying). And the switching circuit was added to avoid confusion on reception and transmittance. The reader attached to a feeding device was developed to transmit activating signal periodically and to identify code of the individual tag when the tag was approached to the device. The reader was consisted of an active filter, a detecter, a comparator and a microcontroller. The test result was feasible enough to apply it for the automatic farm management system and the identified maximum distance was about 37cm.

• Fashion & Textile Research Journal
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• v.22 no.3
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• pp.323-334
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• 2020

This study analyzed the effects of consumers' characteristic variables on information search and purchase decisions in a decision-making process that validated the path model in purchasing apparel products. In constructing a structural equation model using AMOS 19.0., the variables including enjoyment pursuit, price pursuit, product involvement and product risk were selected as consumers' characteristic variables affecting the stage of information search. A questionnaire was distributed to consumers over 20 years old who purchased apparel products using offline and online channels within one year; consequently, we were able to analyze 468 effective data. The results were as follows. First, the path model of this research proved to be the appropriate model explaining the effects of consumers' characteristic variables on the stage of purchase decision-making. Second, enjoyment pursuit had a significant positive influence on offline information search; in addition, price pursuit and product risk affected the online information search significantly. Product involvement affected online information search as well as offline information search. Third, the offline information search affected offline purchase and online information search affected online purchase. However, consumer's channel switching behavior between the stage of information search and the stage of purchase decision was not proven. The findings suggest that companies need to develop distribution strategies according to consumers' characteristic factors that effect consumer's purchase decision-making.

• The Korean Journal of Applied Statistics
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• v.27 no.1
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• pp.123-132
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• 2014

Inflation uncertainty is known to have deleterious effects on facilities investment by disturbing the corporate decision on the opportunity cost of investment. In this paper, we test the validity of this hypothesis in Korea by estimating the inflation uncertainty with both a time-varing parameter model with GARCH disturbances and the relative price volatility and then, estimate the facilities investment equation which includes those uncertainty indicators. The uncertainty indexes estimated by the above-mentioned methods continue to fluctuate even after the inflation rate has dropped dramatically reflecting the structural changes of Korea's economy since the financial crisis in 1997. As a result of estimation of the investment equation by both OLS and GMM, we find the inflation uncertainty has a negative effect on facilities investment with a statistical significance. Moreover, by means of Markov-switching regression model utilized to verify the non-linearity of this relationship, we draw a conclusion that this negative effect of inflation uncertainty heightens asymmetrically during the downturn periods of business cycle.

• Journal of Digital Convergence
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• v.13 no.4
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• pp.89-100
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• 2015

This study focused on analyzing the effects of characteristics of marketing mix on brand image, perception, switching barrier and loyalty of authorized dealers in the Korean CCTV converging channels. This study formulated a structural equational model, in which characteristics of marketing mix was adapted as an exogenous variable and in which brand image, perception of authorized dealer, switching barrier were included as mediator variables, having influences to the endogenous variable such as loyalty of authorized dealers. In this study, 8 hypotheses were formulated, on which this research models were based, in order to test the significance of mediator effects, suggested in the previous articles, that having high significance. This study collected the effective questionnaires of 191 respondents who were the authorized dealers in nationwide and then analyzed with AMOS20 and SPSS20 to test the hypotheses. This study concluded as follows: Product and price in marketing mix had a significant effect on the brand image but only advertising had some effects on the perception of providing parties.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.166-171
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• 2008

This paper presents high efficiency control system of automotive 35W electronic ballast for high intensity discharge(HID) lamp using switching flyback converter with variable frequency. Considering performance, size and efficiency of ballast, the flyback converter is designed with planar transformer in converter stage. HID lamp demands a highly efficient ballast and very complex control circuitry that can control complex transient state for applying to automotive. The proposed electronic ballast system is composed of a flyback converter using planar transformer, a full bridge inverter, and a step up igniter. In this system, switching frequency of flyback converter is controlled by varying input voltage of HID ballast and the price and the size of HID ballast using planar transformer can be reduced. The performance and efficiency of the posed system are verified through various the experiment results.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.109-115
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• 2019

Most demand forecasting studies for telecommunication services have focused on estimating market size at the introductory stage of new products or services, or on suggesting improvement methods of forecasting models. Although such studies forecast business growth and market sizes through demand forecasting for new technologies and overall demands in markets, they have not suggested more specific information like relative market share, customers' preferences on technologies or service, and potential sales power. This study focuses on the telecommunication service industry and explores ways to calculate the relative market shares between competitors, considering competitive situations at the introductory stage of a new mobile telecommunication service provider. To reflect the competitive characteristics of the telecommunication markets, suggested is an extended conjoint analysis using service coverage and service switching rates as modification variables. This study is considered to be able to provide strategic implications to businesses offering existing service and ones planning to launch new services. The result of analysis shows that the new service provider has the greatest market share at the competitive situation where the new service covers the whole country, offers about 50% of existing service price, and allows all cellphones except a few while the existing service carrier maintains its price and service and has no response to the new service introduction. This means that the market share of the new service provider soars when it is highly competitive with fast network speed and low price.

• Economic Analysis
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• v.27 no.4
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• pp.43-69
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• 2021

As the trade linkages and the financial relationship between China and Korea grow stronger, China's influence on Korea is also growing larger. Therefore, it is meaningful to examine key features of Chinese monetary policy operations and the current situation, and to analyze the transmission mechanism of China's monetary policy shocks onto the Korea economy. China's monetary policy shocks can have an impact on the Korea economy through the trade, financial and oil-price channels. In the trade channel, an expansionary Chinese monetary policy can increase Korea's exports of intermediate goods to China under the vertical trade structure, via the vertical trade integration effect. Meanwhile, the expenditure switching effect and the income demand effect show no statistical significance. In the financial and oil-price channels, expansionary Chinese monetary policy shocks can decrease the interest rate and increase both stock prices and the consumer price index in Korea through changes in global portfolio capital flows, interest rates, and raw material prices.

• Journal of the Korea Safety Management & Science
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• v.15 no.4
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• pp.323-330
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• 2013

The number of domestic smartphone users exceeded 30 million people, and the time in the future everyone will use a smartphone that will come with ago. Past purchase decisions, related research and product from the competition between the past case and the relevant literature for the smartphone market smartphone type to derive a purchase decision factors in the decision to purchase any difference between the factors. Literature and practices through performance, switching costs, product loyalty, design, brand, after-sales service, the price more than 7 variables were analyzed. One hundred people surveyed, respectively, did not obtain the response of a variety of ages and occupations, age of the sample used in the analysis of this study, and is concentrated as a student at the university of smartphones used to facilitate users analysis was done. We expect smartphone companies and related companies to be able to give guidelines for effective technology management.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.44-45
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• 2011

Research on photovoltaic (PV) generation is taking a lot of attention due to its infinity and environment-friendliness with decrease of price per PV cell. While central inverters connect group of PV modules to utility grid in which maximum power point tracking (MPPT) for each module is difficult, micro inverter is attached on each module so that MPPT for individual modules can be easily achieved. Moreover, energy generation and consumption efficiency can be much improved by employing direct current (DC) distribution system. In this paper, a digitally controlled PV micro converter interfacing PV to DC distribution system is proposed. Boundary conduction mode (BCM) is utilized to achieve zero voltage switching (ZVS) of active switch and eliminate reverse recovery problem of passive switch. A 120W prototype boost PV micro converter is implemented to verify the feasibility and experimental results show higher than 98% efficiency at peak power and 97.29% of European efficiency.