• Journal of Digital Convergence
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• v.12 no.10
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• pp.317-327
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• 2014

To improve the efficiency of wireless channel, IEEE 802.11ac uses the DL MU-MIMO MAC scheme through which an AP transmits multiple frames to different mobile nodes simultaneously. IEEE 802.11ac DL MU-MIMO MAC needs a new step, called as TXOP sharing, between legacy IEEE 802.11n DL SU-MIMO's two operations, the obtaining an EDCA TXOP and the transmitting multiple frames for EDCA TXOP. In the TXOP sharing operation, both wireless channel destinations and frames transmitted for its TXOP period should are determined. So this paper deals with the TXOP sharing for improving IEEE 802.11ac MAC performance. However, the EDCA priority based method mentioned by IEEE 802.11ac standard document not fair among the buffers and the frames of buffers, and occurs in high_loss rate and high_delay about specific buffers. In this paper, we propose a new scheme of the TXOP sharing with sequencing p-AC, s-AC in similar properties, and all S-AC. This method provides a differentiated service without damage of EDCA characteristics.

• Journal of the Korea Society of Computer and Information
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• v.19 no.2
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• pp.183-191
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• 2014

In this study Cyclomatic Complexity of Web Software has been analyzed quantitatively by correlation between complexity and Number of Classes(NOC), and Number of Methods(NOM) which are object oriented programming measures. Based on the frequency distribution of complexity, NOC and NOM of software at the Web environment, correlation between complexity threshold and NOC threshold, and NOM threshold has been measured and more than 4,000 ASP files of 10 Web real projects have been used as the sample. The empirical result shows that NOC threshold is 21, NOM threshold is 40 and complexity threshold is 68 as high value, and 8 projects among of 10 except 2 projects with especially high frequency distribution shows that NOC threshold is 12, NOM threshold is 21 and complexity threshold is 52 with relatively low value, so correlation has been found out as exists. And also 8 projects with low threshold of complexity, NOC and NOM were internal management software, and the other 2 projects were external sales service software, Number of Classes and Number of Methods can be defined at the design stage according to business properties, and also the complexity can be estimated in order to improve the software quality.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.123-135
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• 2011

The domestic market of database in Korea is estimated to be over 3.663 trillion won. The data migration is getting to be more important along with the continuous growth of the database industry. g-CRM and private recommending function are examples of the service that can be given through coupling among customer database, product database, geographic information database, and others. The core infrastructure is also the database which is integrated, perfect, and reliable. There are not enough researches on efficient way of data migration and integrating process and investigation of migrated data though trends of database in IT environment as above. In connection with this issue, we have made a model for data migration on scientific and technological contents and suggest the result of data migration process adapting that model. In addition, we verified migration's exhaustiveness, migration's consistency, and migration's coherence for investigation of migrated data and database. From the result, we conclude data migration based on proper model has a significant influence on the database consistency and the data values correctness and is essential to maintain high qualified database.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.209-217
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• 2011

Recently, As it takes charge of the customer service in many enterprises, the importance of call center has been emphasized more and more. The growth of call center industry is leading lots of call center agents. But, Call center agent's frequent turnover deteriorates the labor productivity and quality. Also, This turnover increases training cost and recruit cost. For these reasons, management turnover in call center is emerging as an important issue. The purpose of this study is to analyze the relationship of job satisfaction factors, job satisfaction, organizational commitment and turnover intention of call center agent. To achieve these objective, as a conceptual model of the study, job satisfaction factors, job satisfaction, organizational commitment and turnover intention were reviewed and the model could be estimated through path analysis. According th the finding of this study, job satisfaction factors have positively impact on the job satisfaction, organizational commitment but have not directly impact on the turnover intention. Also job satisfaction and organizational commitment have negatively impact on the turnover intention. As a result, the meaningful implication of this study suggests that the increase of both job satisfaction and organizational commitment through the improvement of job satisfaction factors should be regard as important dimensions to decrease of turnover intention of call center agents.

• Journal of Digital Convergence
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• v.14 no.7
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• pp.403-409
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• 2016

This study is a food shopping experience of omni-channel. Food threats and healthy living concerns bring different channels in led to increase reasonable way such as various demand. Omni-channels should be premised on understanding customer behavior as well as empirical user types in which considerations including the value of experience and understanding consumer behavior. Online survey result showed that, (1)offline food shopping, major retail store with quality, buy fresh food directly 2~3 times a month (2)online food shopping, e-commerce site with costs, buy fruits & nuts 2~3 times a month. After in-depth interview with eight high quality participants, I analyzed needs for food shopping experience in regard to the four steps food purchasing journey then derived a persona with integral value 'health' and 'diet'. It is classified into two types. One is the primary persona, family and health oriented, considering household money 'saving', and other is secondary persona, work and personal oriented, looking forward to 'automatic supply'. The result of this study provided an insight that help us explore ways to resolve function and services in the context of a healthy and balanced diet for improving food shopping experience of omni-channel.

• Journal of Digital Convergence
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• v.11 no.10
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• pp.103-122
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• 2013

It has been realized that the flavor of coffee depends on the coffee-producing region and the growing condition. It has also been realized that the species of coffee beans influence the taste of coffee. However, coffee education is currently underway mainly for the simple job training of baristas such as roasting, extracting and customer service, and very little education on green coffee is being done. Therefore, this study is to contribute to the basic research material for the curriculum development of green coffee education. Through surveys to coffee instructors and students to investigate the current situation of green coffee education and awareness level of green coffee, the requirements of green coffee education has been analyzed. Further, the teaching direction and learning factors of green coffee have also been analyzed through Interview Analysis to coffee professionals. Based on the result thereof, this study is to suggest systematic lecturing-learning standards by presenting an education goal of green coffee, selection of education contents, determination of subject name, and composition and listing of education units to be learned. This study will be one of the basic research materials to plan and design the curriculum for green coffee education.

• Culinary science and hospitality research
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• v.21 no.1
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• pp.250-266
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• 2015

This study concentrated on the dining out consumption behaviors, dining out selection attributes, and changes in eating habits of silver generation. Total 216 residents in metropolitan area were employed for statistical analysing. The results are as follows. First, as the result of t-test and ANOVA showed that female and higher academic background tended to regularly take high level of fruits, vegetables, meat, and fish eating habits. These results identified that dining out culture and dietary lifestyle are closely linked. Second, as the result of difference in dining out consumption attitudes on eating habit of silver generation, consumers who have better eating behaviors tended to consider the physical environment, variety of menu, and service quality when they choose a restaurant. Third, as the result of analysis on changes in dining out consumption behavior based on eating behavior of silver consumers, groups differences were found from only the source for information on dining out business and standard variable in selection of dining out business. Fourth, physical environment, variety of menu, business quality, and service were indicated as significant selection attributes of dining out among silver peoples. Fifth, dining out consumption behaviors of silver consumers were developed through newspapers, magazines, and previous visiting experiences. In conclusion, the results of present study showed that silver consumers tend to select a restaurant based on word-of-mouth and various factors related to experiences. Hence, various promotional activities are necessary for the business succession.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1A
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• pp.25-33
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• 2003

We derive the outage probabilities for the Erlang capacity and link margin based on handoffs in the reverse link of a CDMA system of 14.4 kbps/1.9 GHz band, calculate them with the same parameters, and then with the maximum realizable Erlang capacity analyze newly the cell coverage in different areas by the COST-231 model If it decreases from 5 % to 2 % in case of $E_b/N_0$=5 dB under a soft handoff, the result shows a very reliable link with additional increment of 0.88 dB in the margin and a high quality of service within the coverage decrease of 0.12 km, 0.25 km, and 1 km in a city, suburban, and open areas respectively on the decrease of 2 Erlang in the capacity. When the $E_b/N_0$ decreases from 7 dB to 5 dB within the outage probability of 5 %, it shows the increase of 9 Erlang and of 0.2 km in a city on the same margin of 2.8 dB. Then, comparing it with a single cell, it shows the decrease of more than 10 Erlang in the capacity, but the enlargement of 0.17 km, 0.3 km, and 1 km in them on the margin decrease of 1.31 dB, also, with a hard handoff, the soft handoff gain of the increase of 10 Erlang and of 0.22 km, 0.5 km, and 2 km on the decrease of 2.16 dB.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.65-76
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• 2002

QoS routing is a routing technique for finding feasible path that satisfies QoS requirements required by application programs. Since QoS routing determines such paths in terms of dynamic network state, it satisfies the requirement of applications and increases the utilization of the network. The overhead is, however, generated by routers to exchange the information of the dynamic state of network. In order to reduce this protocol overhead, a timer based update mechanism is proposed in which router checks the change of the network status periodically and network state information is exchanged if the change is greater than a certain value. Using large update period makes, though, routing performance irresponsive to the parameters which determine the update of the network state of the router. In addition to this, large update period may result in inaccurate network state information at routers and cause resource reservation failure. The resource reservation failure generates additional overhead to cancel the resource reservation of the part of the path. In this paper, we propose mechanisms enhancing the existing network state update policy with respect to these two problems. Performance of the proposed schemes are evaluated through a course of simulation.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.1-14
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• 2002

The most important issue in providing multimedia traffic on a mobile computing environments is to guarantee the mobile host(client) with consistent QoS(Quality of Service). However, the QoS negotiated between the client and network in one cell may not be honored due to client mobility, causing hand-offs between cells. In this paper, a call admission control mechanism is proposed to provide consistent QoS guarantees for multimedia traffics in a mobile computing environment. Each cell can reserve fractional bandwidths for hand-off calls to its adjacent cells. It is important to determine the right amount of reserved bandwidth for hand-off calls because the blocking probability of new calls may increase if the amount of reserved bandwidth is more than necessary. An adaptive bandwidth reservation based on an MPP(Mobility Pattern Profile) and a 2-tier cell structure has been proposed to determine the amount of bandwidth to be reserved in the cell and to control dynamically its amount based on its network condition. We also propose a call admission control based on this bandwidth reservation and "next-cell prediction" scheme using an MPP. In order to evaluate the performance of our call admission control mechanism, we measure the metrics such as the blocking probability of our call admission control mechanism, we measure the metrics such as the blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of the existing mechanisms such as NR-CAT1, FR-CAT1, and AR-CAT1.