• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1631-1636
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• 2015

With the advance of wireless communication technology in terrestrial area, underwater communication is also evolving very fast from a simple point-to-point transmission to an elaborate networked communications. Underwater acoustic channel has quite different features comparing with the terrestrial radio channel in terms of propagation delay, Doppler shift, multipath, and path loss. Thus, existing technologies developed for terrestrial communication might not work properly in underwater channel. Especially medium access control (MAC) protocols which highly depend on propagation phenomenon should be newly designed for underwater network. CSMA/CA has drawn lots of attention as a candidate of underwater MAC protocol, since it is able to resolve a packet collision and the hidden node problem. However, a received signal could be degraded by the interferences from the nodes locating outside the receiver's propagation radius. In this paper, we study the effects of interference on the CSMA/CA based underwater network. We derived the SNR with the interference using the sonar equation and analyzed the degradation of the RTS/CTS effects. These results are compared with the terrestrial results to understand the differences. Finally we summarized the design considerations in CSMA/CA based underwater network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.623-628
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• 2013

The retrodirective array antenna system is operated faster than existing techniques of beamforming due to its less complexity. Therefore, it is effective for beam tracking in the environment of fast vehicle. On the other hand, it also has difficulty in estimating AOA according to multipath environment or multiuser signals. To improve the certainty of estimating AOA), this article proposes hybrid digital retrodirective array antenna systme combined with MUSIC algorithm. In this paper, the digital retrodirective array antenna system is designed according to the number of antenna array by using only one digital PLL which finds angle of delayed phase. And we evaluate the performance of the digital retrodirective array antenna for the high speed tracking application. Performance is studied by simulink when the speed of mobile is 300km/h and the distance between transmitter and receiver is 100m and then we have to confirm the performance of the system in multi path environment. As a result, the mean of AOA (Angle Of Arrival) error is $4.2^{\circ}$ when SNR is 10dB and it is $1.3^{\circ}$ when SNR is 20dB. Consequently, the digital RDA shows very good performance for high speed tracking due to the simple calculation and realization.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.89-99
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• 2005

Advances of Internet and rC accelerate distribution and sharing of information, which make P2P(Peer-to-Peer) computing paradigm appear P2P computing Paradigm is the computing paradigm that shares computing resources and services between users directly. A fundamental problem that confronts Peer-to-Peer applications is the efficient location of the node that stoles a desired item. P2P systems treat the majority of their components as equivalent. This purist philosophy is useful from an academic standpoint, since it simplifies algorithmic analysis. In reality, however, some peers are more equal than others. We propose the P2P protocol considering differences of capabilities of computers, which is ignored in previous researches. And we examine the possibility and applications of the protocol. Simulating the Magic Square, we estimate the performances of the protocol with the number of hop and network round time. Finally, we analyze the performance of the protocol with the numerical formula. We call our p2p protocol the Magic Square. Although the numbers that magic square contains have no meaning, the sum of the numbers in magic square is same in each row, column, and main diagonal. The design goals of our p2p protocol are similar query response time and query path length between request peer and response peer, although the network information stored in each peer is not important.

• Journal of Distribution Science
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• v.13 no.5
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• pp.103-111
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• 2015

Purpose - When it comes to first impressions of family restaurants, people basically think of the following factors: cozy, a refreshing space, indoor lighting, atmospheric music, the best-quality service through mutual interactions with employees, birthday events, follow-up customer management, brand image, and many others. Focusing on such family restaurants characteristics, with consumption experience and customer satisfaction determined as mediator variables, this study looks into the selection factors that affect customer loyalty when choosing a family restaurant. Subsequently, the study conducts an empirical analysis of these selection factors with the greatest influence. Research design, data, and methodology - This study analyzed 200 total surveys of family restaurant customers including college students, workers, housewives, and others. The survey was conducted over two weeks in May 2014. For statistical processing, SPSS 21 was used for factor analysis and reliability analysis as well as AMOS for structural equation analysis. In terms of a variable that would influence either consumption experience or customer satisfaction at the restaurants, the study introduced the concept of customer equity. The study designed a model based on a hypothesis developed using the following factors: customer encounter service value, customer convenience value, brand equity, relationship equity, and other factors defined as components of customer equity by Rust et al. (2000) determined as independent variables as well as with customer experience and customer satisfaction set as mediator variables. The hypothesis, after all, assumed that customer loyalty would be positively (+) influenced. Results - The analysis results from the study reported that brand value, customer encounter service value, and relationship value have positive (+) effects on consumption experience and customer satisfaction. However, as for customer convenience value, this turned out not to have a statistically significant influence on consumption experience and customer satisfaction. In regard to a relation between consumption experience and customer satisfaction, the results showed that the former affects the latter, and in terms of intervening variables, both of these appeared to have a positive (+) effect on customer loyalty. Conclusions - This study suggests that family restaurants should look for strategies that focus on how to promote customer relationships. For example, restaurants could try birthday events or discount events to achieve this goal. Since the study ended up realizing relatively low levels of suitability and statistical significance, the path of the study changed. After all, in order to increase suitability and statistical significance, the study had to eliminate factors such as service quality and others and for this reason the study was unable to conduct the analysis as initially planned. In addition, the data samples of the research were mainly gathered from students, which made it hard to say that the analysis was carried out on samples from every different group. Future research should analyze the characteristics of each group of customers for factors affecting customer satisfaction and customer loyalty in the family restaurant chain.

• Journal of Distribution Science
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• v.12 no.9
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• pp.101-112
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• 2014

Purpose - Recently, although corporate social responsibility activities have been increasing in size, they do not have to achieve qualitative improvements and can be passive and cost consuming. Therefore, companies should make quantitative as well as qualitative improvements in their efforts in corporate social responsibility activities. In this study, the classification of social responsibility activities in a variety of studies was analyzed through a more specific path than in previous studies. Corporate behavior image, social behavior image, and corporate contributions image were analyzed through a more detailed analysis of performance. This study suggests that more detailed and concentrated social responsibility activities be pursued by forming companies. Research design, data, and methodology - The purpose of study is to gauge the corporate need for a more intensive, specific area of CSR activities. For this purpose, the sample of consumers that were targeted for CSR activities, recognized as 261 persons, have been investigated. Through a theoretical discussion on previous research, nine hypotheses were established on corporate image, the influence of corporate performance on CSR, and the CSV regulation effect. In order to test the hypothesis, a survey was conducted on 261 male and female consumers who were targeted for CSR, being persons in their 20s to 40s. PASW Statistics 18.0 and AMOS 18.0 were used for statistical analysis. Results - Corporate behavior image was formed through legal responsibility activities and economic responsibility activities. In addition to economic responsibilities, ethical responsibilities and environmental responsibilities were confirmed to have influence on social behavior image. Corporate social responsibility and philanthropic responsibility were confirmed to have influence on economic contribution image. Corporate image has positive effects on brand attitude, corporate reputation, and corporate competition. In addition, when CSV awareness is high, consumers perceive corporate image only through economic responsibility. However, when CSV awareness is low, economic responsibility as well as legal responsibility through charitable activities form the corporate image that influences the brand attitude and corporate reputation, as well as corporate competitiveness. It would appear that the area of corporate social responsibility needs more intensive management for corporate image and corporate competitive advantage. Conclusion - First, the findings of this study show that each CSR activity has a different effect on corporate image and thus, the corporate image influences corporate performance in distinct ways, depending on the CSR activity. This implies that reactive strategies should be tailored to the required image. Second, there is a difference in CSV awareness between groups. When the CSV awareness is low, we can confirm that legal responsibility activities have an especially significant effect on corporate image, implying that corporations should pursue their economic objectives within legal regulations and need to invest significant time and effort for this. This study has limited generalization potential because the result of the model fit has insufficient reference value. In future research, we need to approach various dimensions of corporate performance.

• Journal of Distribution Science
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• v.11 no.10
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• pp.17-25
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• 2013

Purpose - This study analyzes the effect of customers' perceived service innovativeness of service centers for electronic goods, on repurchase intentions of customers, using behavior intentions of service centers as a mediator variable. In customer management and customer relationship marketing, service centers can be the most representative customer relationship management departments because they are most closely placed at the interface with customers. In addition, this study intends to investigate if continuous relationship with customers during one-time product-selling can affect their repurchase intentions. Specifically, this research aims to investigate if the expansion of the saturated physical market of the manufacturing business, to intangible service markets, can be competitive enough to satisfy customer needs. Research design, data, and methodology - This study targets college students, and especially those who have computers, digital cameras, or cell-phones, and often use electronic products and services. In order to investigate our hypothesis, we analyzed dates through SEM (structural equation modeling) using SPSS for Windows 18.0 and AMOS 18.0. In addition, we measured Cronbach's α coefficient using SPSS for Windows 18.0 in order to measure reliability. Further, using AMOS 18.0, this research statistically measured convergent validity as well as discriminant validity, and examined mediation models and path models in which service innovativeness leads to customers' repurchase intentions of electronic products. Results - As a result, this research shows that customers' perceived service innovativeness of service centers for electronic goods has significant positive influence on customers' behavior intentions of service centers. In addition, service innovativeness of electronic goods' service centers also has significant positive influence on repurchase intentions of customers. Conclusion - This study investigates the effect of customers' positive relation with the innovativeness of electronic service center on their behavior intention and product repurchase. The more concrete, important results of the study are as follows. Through the mediating effect, the findings of the study suggest that customers' behavior intentions of service centers partially mediate the effect of customers'perceived service innovativeness of service centers for electronic goods on customers' repurchase intentions. This research also provides an insight that the importance of service innovativeness and innovative approaches in managing customers should be recognized in the process of repurchase and service roles of manufacturing business as a way for customer management. As a result, the relationship between customer satisfaction and service quality of service centers for the electronic products is very sensitive. Although previous studies focus on certain aspects of the case for enhancing service innovation (Kim, 2012), this research recommends that the service centers need to understand the customers'desire first and try to adapt to achieve customer satisfaction by being innovative. This innovativeness of service centers would make customers visit them consistently, which in the long run, will also influence their repurchase decisions.

• Journal of Distribution Science
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• v.11 no.4
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• pp.51-60
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• 2013

Purpose - The objective of this paper is to investigate the effect of asset specificity, the level of information sharing, the importance of information sharing, and an integrated collaborative environment on supply chain performance. Research design, data, and methodology - Data collection was implemented as follows: questionnaires were distributed to 250 companies that have business ties with Halla Climate Control Corporation. The empirical study to test our hypothesis was based on statistical analysis (using SPSS 18.0 and AMOS 18.0). The hypothesis of this paper is that the asset specificity variable has positive effects on the following variables: Level of information sharing, the importance of information sharing, and integrated collaborative environment. Moreover the variables, the level of information sharing, and the importance of information sharing are strongly influenced by the variable integrated collaborative environment, and these when combined, have an effect on the dependent variable, supply chain performance. We tested our hypothesized model utilizing path analysis with latent variables. Results - According to the results of our analysis, hypothesis H1, which tests whether there is a relationship between asset specificity and the integrated collaborative environment, is supported at the 0.01 level. Hypotheses H2 and H3 were also confirmed, and asset specificity had positive effects (+) on the level of information sharing variable. The importance of the information sharing variable was statistically significant at the 0.01 level. Hypotheses H4 and H5 posited that the integrated collaborative environment variable would have a positive effect on the level of information sharing; the importance of information sharing variable was strongly supported statistically, with a significant p-value below. Moreover, the level of information sharing (H6), and the importance of information sharing (H7) variables also had a statistically relevant influence on supply chain performance. As a result, existence of a collaborative system between companies would influence supply chain performance by strengthening real-time information access and information sharing. Thus, it is important to construct a collaborative environment where information sharing among companies and cooperation is possible. Conclusions - First, with rapid changes in the business environment, it becomes necessary for enterprises to acquire the right information in order to properly implement SCM. For successful SCM, firms should understand the importance of collaboration with supply chain partners and an internally built collaboration system, which in turn will better promote a partnership commitment with suppliers as well as collaborative integration with buyers. A collaborative system, as we suggest in this paper, facilitates the maintenance of a long-term relationship of trust, and can help reinforce information sharing. Second, it is necessary to increase information sharing over time via a collaborative system so that employees of the suppliers become aware of the system. The more proactive and positive attitudes are towards such a collaborative system by the managerial group, the higher the level of information sharing will be among the users. Successful SCM performance is achieved by information sharing through a collaborative environment rather than by investing only in setting up an information system.

• Journal of Distribution Science
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• v.11 no.4
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• pp.73-80
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• 2013

Purpose - As the smart-phone market adds new technologies and introduces new marketing trends, competition among companies is getting fierce. Now, smart-phone companies need to pay attention not only to attaining new customers but also to retaining customers, which means managing relationships to prevent customer defection. Therefore, how to satisfy customer needs and maintain long-term relations are both important to make consistent progress in the rapidly changing smart-phone market. To illustrate this point, the study focuses on analyzing the effects of consumption value on relational factors and buying intentions among smart-phone users. First, consumption value was divided into functional, economic, and emotional values. After that, the effects of these values on satisfaction and brand trust were confirmed. Additionally, effects of satisfaction and brand trust on repurchase intention were analyzed. Research design, data, and methodology - The data was collected in a self-administered survey among 270 undergraduate students, using smart-phones between June 4th-12th, 2012. A total of 257 questionnaires were collected and used for the data analysis. A path analysis based on Lisrel 8.54 was used for the hypothesis test. Consumption value was divided into functional, economic, and emotional values. Subsequently, the effects of these values on satisfaction and trust in the brand were confirmed. Additionally, the effects of satisfaction and trust in the brand on repurchase intention were analyzed. Results - First, functional value, economic value, and emotional value - especially emotional value - were revealed to have positive effects on satisfaction. Second, emotional value was shown to have positive effects on brand trust, while functional and economic values did not. Third, satisfaction had positive effects on brand trust. In considering the relative influence on brand trust, satisfaction was the most crucial factor. It is clear that in the evaluation of the direct experience, using the product or the service plays an important role in building brand trust. Fourth, satisfaction and brand trust positively influenced repurchase intention. This indicates that both factors must be achieved to induce the repurchase Intention among customers. Conclusions - One can see that the enjoyable emotions consumers feel while using smart-phones is the most important factor in increasing levels of satisfaction. Moreover, this indicates that consumers pursue economic desires along with convenient functions in order to reduce opportunity costs. Additionally, consumers are affected by psychological and emotional messages in building trust, rather than practical and rational ones. Thus, in order to appeal to young clients as an attractive brand in the smart-phone market, approaching customers with an emotional value is recommended. In addition, in order for the brand to gain trust, the overall experience the consumer feels while using smart phones should be maximized. After all, one must fulfill the consumers' desire for a new experience and show a willingness to faithfully accomplish the responsibility of the brand to strengthen relationships with customers in the smart-phone market.

• The Journal of Industrial Distribution & Business
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• v.8 no.5
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• pp.95-109
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• 2017

Purpose - The purpose of this study is to classify the quality factors of coffee shop customers with the service quality based on the SERVQUAL, selection attributes, and service qualities used in previous studies. The path structure of coffee shops' quality factors → customer satisfaction → trust → behavioral intention was analyzed in order to confirm the system of coffee shops' quality factors. Research design, data, and methodology - The survey of was conducted with college students of Kangwon University. A total of 250 questionnaires were distributed, with 232 collected. Of them, Excluding 36 respondents' because of incomplete answers and missing values, 196 responses were used in the final analysis. Empirical analysis was made through factor analysis, correlation analysis, multiple regression analysis, simple regression analysis and mediating regression analysis by using Statistics Package SPSS 19.0. Results - The results are as follows: Firstly, coffee shops' quality factors were classified into seven categories like service encounter quality, product quality, cleanliness, overall interior, purchase quality, convenience, and aesthetics. Secondly, service encounter quality, product quality, purchase quality, and aesthetics had a positive effect on customer satisfaction, respectively. Thirdly, it showed that service encounter quality, product quality, overall interior, purchase quality, and aesthetics had a positive effect on trust, respectively. Fourthly, customer satisfaction had a positive effect on behavioral intention. Lastly, after verifying the effect relations of trust between customer satisfaction about coffee shop and behavioral intention, customer satisfaction has a positive effect on trust and trust has a positive effect on behavioral intention. On the other hand, trust did not have a mediating effect between customer satisfaction and behavioral intention. But, cleanliness, convenience, and overall interior did not have a positive effect on customer satisfaction. Conclusions - Coffee shop consumers put importance on price, discount systems, taste, and freshness, but more on courteous and kind services of coffee shop staff or comfortable and calming atmosphere of inner space. Thereby, coffee shop marketers need to take factors like service encounter quality and aesthetics into more consideration. In addition, customer satisfaction has an effect on trust, while trust on behavioral intention, even though trust is not mediated between customer satisfaction and behavior intention.

• Journal of Korean Physical Therapy Science
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• v.27 no.2
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• pp.25-35
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• 2020

Background: There are many situations where walking in an actual community needs to change direction along with walking on a straight path, and this situation needs to be reflected in assessing walking ability of the community. Therefore, in this study, we tried to determine whether the assessments can distinguish the level of walking in the community. Design: Retrospective cohort study. Methods: Fifty-two survivors with chronic stroke have participated in the study. According to the evaluation result of 10mWT, the subjects of 0.8m/s and above were classified as the group who could walk in the community (n=22), and the subjects of 0.4m/s~0.8m/s were classified into the group who could not walk in the community (n=30). Modified Rivermead Mobility Index, Postural Assessment Scale for Stroke, Fugl-Meyer Assessment, Berg Balance Scale, 10-meter Walk Test (10mWT) were used to evaluate the motor skills. Furthermore, Activities-specific Balance Confidence Scale was used to evaluate psychological factors, and Timed Up & Go Test (TUG), Figure-of-Eight Walk Test (F8WT), Four Square Step Test (FSST), Step Test (ST) were applied to evaluate dynamic balance and mobility. Results: As a result for distinguishing walking levels in the community, TUG was 14.25 seconds, F8WT was 13.34 seconds, FST was 19.43 seconds, and ST of affected side and non-affected side were 6.5 points and 7.5 points, respectively. TUG (AUC=0.923), F8WT (AUC=0.905), and FST (AUC=0.941) were highly accurate, but the ST of affected side and non-affected side (AUC=0.806, 0.705) showed the accuracy of the median degree, respectively. Conclusion: To distinguish walking levels in the community of survivors with chronic stroke, TUG and FSST have been found to be the best assessment tool, and in particular, FSST could be very valuable in clinical use as the most important assessment tool to distinguish walking levels in the community.