• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10A
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• pp.962-968
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• 2002

Reliable high-speed data communications over insufficient channel bandwidth is one of the major challenges of harsh wireless environments that push the achievable spectral efficiency far below its theoretical limits. A Quadrature amplitude modulation (QAM) scheme is a userful modulation technique for achieving high data rate transmission without increasing the bandwidth of wireless communication systems. The exact general bit error rate (BER) expression of arbitrary rectangular quadrature amplitude modulation has not yet been derived. In this paper, a generalized closed-form expression for the BER performance of rectangular QAM with Gray code bit mapping is derived and analyzed in the presence of additive white Gaussian noise (AWGN) channel. First we analyze the BER performance of an I-ary PAM scheme. Regular patterns in the k-th bit error probability are observed while developing the EBR expression. From these patterns we provide the exact and general closed-from EBR expression of an I-ary PAM. Then we present a general closed-from expression for BER of an arbitrary IXJ rectangular QAM by considering that this signaling format consists of two PAM scheme, i.e., I-ary and J-ary PAM. A simple approximate BER expression for rectangular QAM is given as well.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.8
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• pp.1128-1140
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• 2002

As consumers' alternatives in fashion store selection increase, they select different store types to purchase different product types. Therefore, the probability of patronage mix behavior according to product type increases. Understanding consumers patronage mix behavior, finding out the determinant attributes of fashion stores for each product type are important to retailers and marketers for building a successful merchandising and marketing strategies. Most of the previous researches in store selection and patronage assume consumer behavior as single store patronage, and thus relatively little is known about patronage mix behavior. Also, little attention has been given to product characteristics as an important variable in store patronage behavior. The purposes of this study were to determine the effects of product characteristics in consumers patronage mix behavior. In this study, a theoretical model including product characteristics as an intervening variable between store attributes and patronage behavior was developed. A Questionnaire was developed and data were collected form 464 adult women living in Seoul area in Korea. Factor analysis, paired t-test, ANOVA, Duncan test and discriminant analysis were employed to analyze the data. As a result, the suggested model was partially verified. First, the product characteristic was found to have an effect on perceived importance of store attributes and on determinant attributes of stores. Consumers were found to use different evaluative criteria for store attributes when they purchase different product types. Second, the perceived importance of store attributes was determined by consumer characteristics as well as product characteristics. Third, the determinant attributes in store selection were affected not only by the perceived importance of store attributes but also by the type of product to be purchased.

• Journal of Korea Trade
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• v.23 no.5
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• pp.129-144
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• 2019

Purpose - Recent empirical studies have reached mixed results on the effects of financial liberalization and currency crises. We argue that this relationship is likely to depend both on whether controls are primarily on the degrees of financial liberalization and on the stability of the government. Using the disaggregated data on financial liberalization recently developed by Abiad et al (2010) for a sample of 30 emerging countries over the period 1995-2015, we attempt to investigate the political economy determinants of currency crises. Design/methodology - Our empirical model considers the relationship between financial liberalization and currency crises for emerging market economies. This study employs the existing theoretical framework to identify the disaggregate level for financial liberalization across countries. Using a multivariate logit model, this study attempts to estimate the interrelationship among financial liberalization, government stability and currency crises complemented by a case study of South Korea. Findings - Our main findings can be summarized as follows: we find strong support for the proposition that more liberalized financial institutions are positively associated with the probability of currency crises especially under less stable governments, but reduce the risks of currency crises especially for more stable governments. We also examine the role of financial systems with the case of South Korea after Asian financial crises and the results are further supported and consistent with the empirical findings. Originality/value - Existing studies focus on the economic factors across countries. This paper instead attempts to evaluate the effects of financial liberalization and currency crises by incorporating political considerations with newly developed dataset on financial liberalization, which are essential to the understanding of the causes of currency crises.

• Architectural research
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• v.21 no.3
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• pp.59-67
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• 2019

Although many stadiums around the world have incorporated various profitable facilities, many are making conventional and cursory decisions without deep consideration of the interrelationships of different programs. This paper investigates cases in which new programs such as a hotel, a youth hostel, and a dormitory have been introduced into stadiums, showing different results. In the first part of this paper, the theoretical precedents of program combination are studied. Although Bernard Tschumi's notion of the combination of different programs presented its prophetic probability, this paper discern different approaches addressing program mixture, engendering eventually a productive modification of his notion based on the empirical observation of the cases. This paper classifies the manner of programmatic combination into complexity and hybridity, arguing that the latter transforms the spaces and gives rise to unexpected synergy, while the former merely assembles different programs. The second part compares the spaces of complexity and hybridity in stadiums. Through the plan and the section analysis of the spatial structure and the interrelationship of programs, this section reveals how the two different ways of the program combinations have had different results. In hybrid stadiums, programs are not simply gathered, but directly connected and intertwined. In the third part, the nature of the spatial transformation in the hybrid space is researched in detail. In the hybrid stadiums, the collision of the different programs changes the conception of the programs themselves and their related spaces. Hotels and stadiums are not what they once were, provoking unanticipated situations. These transformed spaces not only suggest a method of reutilizing of disused urban spaces, but also of meaningful and communicative program mixture, diversifying and vitalizing a city, not isolated islands of discrepancy. The ultimate purpose of this paper is clarifying the programmatic hybrid paradigm, surpassing complexity through the analysis of the stadium cases and illuminating the manner by which the hybridity breaks the typical tie between the program and space, to cause transformed situations.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.995-1002
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• 2020

This paper investigates the achievable data rate for non-orthogonal multiple access(NOMA) with correlated information sources(CIS), under the binary phase shift keying(BPSK) modulation, in contrast to most of the existing NOMA designs using continuous Gaussian input modulations. First, the closed-form expression for the achievable data rate of NOMA with CIS and BPSK is derived, for both users. Then it is shown by numerical results that for the stronger channel user, the achievable data rate of CIS reduces, compared with that of independent information sources( IIS). We also demonstrate that for the weaker channel user, the achievable data rate of CIS increases, compared with that of IIS. In addition, the intensive analyses of the probability density function(PDF) of the observation and the inter-user interferennce(IUI) are provided to verify our theoretical results.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.125-125
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• 2020

European Space Agency's Sentinel-1 has an improved spatial and temporal resolution, as compared to previous satellite data such as Envisat Advanced SAR (ASAR) or Advanced Scatterometer (ASCAT). Thus, the assumption used for low-resolution retrieval algorithms used by ENVISAT ASAR or ASCAT is not applicable to Sentinel-1, because a higher degree of land surface heterogeneity should be considered for retrieval. The assumption of homogeneity over land surface is not valid any more. In this study, considering that soil roughness is one of the key parameters sensitive to soil moisture retrievals, various approaches are discussed. First, soil roughness is spatially inverted from Sentinel-1 backscattering over Yanco sites in Australia. Based upon this, Artificial Neural Networks data (feedforward multiplayer perception, MLP, Levenberg-Marquadt algorithm) are compared with Fractal approach (brownian fractal, Hurst exponent of 0.5). When using ANNs, training data are achieved from theoretical forward scattering models, Integral Equation Model (IEM). and Sentinel-1 measurements. The network is trained by 20 neurons and one hidden layer, and one input layer. On the other hand, fractal surface roughness is generated by fitting 1D power spectrum model with roughness spectra. Fractal roughness profile is produced by a stochastic process describing probability between two points, and Hurst exponent, as well as rms heights (a standard deviation of surface height). Main interest of this study is to estimate a spatial variability of roughness without the need of local measurements. This non-local approach is significant, because we operationally have to be independent from local stations, due to its few spatial coverage at the global level. More fundamentally, SAR roughness is much different from local measurements, Remote sensing data are influenced by incidence angle, large scale topography, or a mixing regime of sensors, although probe deployed in the field indicate point data. Finally, demerit and merit of these approaches will be discussed.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.549-555
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• 2023

Jacking force loss management inside the PSC Box girder of a common high-speed railway is a very important feature in girder performance, and requires detailed management during the maintenance of the girder. This study aimed to analyze the timing of re-tension prediction of PSC Box girder based on the reduction level of the packing force inside the girder and the results of the tension loss measured without the train load test. As a result of predicting the timing of re-tension according to the level of tension reduction of the PSC Box Girder, the Jacking Force Loss curve was gently analyzed before the structure reached 17 years after confirmed completion, and 17 years later, it was found that the jacking force loss curve progressed rapidly. The results confirmed that the tension of the structure decreases with the service life increase, but considerably decreases as the structure ages. Therefore, more data and research on tension loss of facilities over 20 years are much required.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.6
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• pp.1619-1637
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• 2016

With wide distribution of smart phones and development of mobile network, social network service (SNS) is displaying remarkable growth rates. Users build new social relations by sharing their interests, which brings surging growth to the SNS based on the combination between the strength of expanding the place for communication and distribution of smart phones featured with easy portability. This study is designed to understand impact factors of SNS on users in Korea and to conduct empirical research on casual relationship between the factors above and the factors affecting personal information behavior through the privacy protection and self-efficacy. In order to accomplish the objective above, the study presented a research model applied with key variables of the Health Belief Model (HBM) predicting behaviors capable of recognizing and preventing individual diseases in the field of health communication. To perform empirical verification on the research model of this study, a survey was conducted upon college students at N university located in Chungcheongnam-do and K university in rural area, who have experiences using the SNS. Through this survey, a total of 186 samples were collected, and path analysis was performed in order to analyze the relationship between the factors. Based on the findings from the survey, first, variables Perceived probability, Perceived severity, Perceived impairment of the HBM, key factors of personal information protection behavior on the SNS, were found to exhibit negative relationship with self-efficacy, and Perceived probability, Perceived benefit, Perceived impairment were found to exhibit negative relationship with privacy protection. But the above, Perceived severity showed positive relationship with privacy protection, and Perceived benefit and self-efficacy also displayed positive relationship. Second, although self-efficacy, a parameter, showed positive relationship with privacy protection, it demonstrated negative relationship with personal information protection behavior. Lastly, privacy protection exhibited positive relationship with personal information protection behavior. By presenting theoretical model reflected with characteristics of prevention based on these findings above unlike previous studies on personal information protection using technologies threatening personal information, this study is to provide theoretical and operational foundation capable of offering explanations how to predict personal information protection behavior on the SNS in the future.

• KDI Journal of Economic Policy
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• v.12 no.1
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• pp.127-148
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• 1990

A Milgrom-Roberts style signalling model of limit pricing is developed to analyze the possibility and the scope of limit pricing in general, noncooperative oligopolies. The model contains multiple incumbent firms facing a potential entrant and assumes an information asymmetry between incombents and the potential entrant about the market demand. There are two periods in the model. In period 1, n incumbent firms simultaneously and noncooperatively choose quantities. At the end of period 1, the potential entrant observes the market price and makes an entry decision. In period 2, depending on the entry decision of the entrant, n' or (n+1) firms choose quantities again before the game terminates. Since the choice of incumbent firms in period 1 depends on their information about demand, the market price in period 1 conveys information about the market demand. Thus, there is a systematic link between the market price and the profitability of entry. Using Bayes-Nash equilibrium as the solution concept, we find that there exist some demand conditions under which incumbent firms will limit price. In symmetric equilibria, incumbent firms each produce an output that is greater than the Cournot output and induce a price that is below the Cournot price. In doing so, each incumbent firm refrains from maximizing short-run profit and supplies a public good that is entry deterrence. The reason that entry is deterred by such a reduced price is that it conveys information about the demand of the industry that is unfavorable to the entrant. This establishes the possibility of limit pricing by noncooperative oligopolists in a setting that is fully rational, and also generalizes the result of Milgrom and Roberts to general oligopolies, confirming Bain's intuition. Limit pricing by incumbents explained above can be interpreted as a form of credible collusion in which each firm voluntarily deviates from myopic optimization in order to deter entry using their superior information. This type of implicit collusion differs from Folk-theorem type collusions in many ways and suggests that a collusion can be a credible one even in finite games as long as there is information asymmetry. Another important result is that as the number of incumbent firms approaches infinity, or as the industry approaches a competitive one, the probability that limit pricing occurs converges to zero and the probability of entry converges to that under complete information. This limit result confirms the intuition that as the number of agents sharing the same private information increases, the value of the private information decreases, and the probability that the information gets revealed increases. This limit result also supports the conventional belief that there is no entry problem in a competitive market. Considering the fact that limit pricing is generally believed to occur at an early stage of an industry and the fact that many industries in Korea are oligopolies in their infant stages, the theoretical results of this paper suggest that we should pay attention to the possibility of implicit collusion by incumbent firms aimed at deterring new entry using superior information. The long-term loss to the Korean economy from limit pricing can be very large if the industry in question is a part of the world market and the domestic potential entrant whose entry is deterred could .have developed into a competitor in the world market. In this case, the long-term loss to the Korean economy should include the lost opportunity in the world market in addition to the domestic long-run welfare loss.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.92-102
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• 2017

Fischer-Tropsch synthesis reaction converts syngas (mixture of CO and H2) to valuable hydrocarbon products. Simulation of low temperature Fischer -Tropsch Synthesis reaction and heat transfer at intensified process condition using catalyst filled single and multichannel microchannel reactor is considered. Single channel model simulation indicated potential for process intensification (higher GHSV of $30000hr^{-1}$ in presence of theoretical Cobalt based super-active catalyst) while still achieving CO conversion greater than ~65% and $C_{5+}$ selectivity greater than ~74%. Conjugate heat transfer simulation with multichannel reactor block models considering three different combinations of reactor configuration and coolant type predicted ${\Delta}T_{max}$ equal to 23 K for cross-flow configuration with wall boiling coolant, 15 K for co-current flow configuration with subcooled coolant, and 13 K for co-current flow configuration with wall boiling coolant. In the range of temperature maintained (498 - 521 K), chain growth probability calculated is desirable for low-temperature Fisher-Tropsch Synthesis.