Lee H.C.,Yuhan University
Applied Mechanics and Materials | Year: 2014
This paper analyzes a MAC (Medium Access Control) layer throughput over error-prone channel in the IEEE 802.11ac-based wireless LAN with DCF (Distributed Coordination Function) protocol and A-MPDU (MAC Protocol Data Unit Aggregation) scheme, using theoretical analysis method. The MAC saturation throughput is evaluated by using a PER (Packet Error Rate) on the condition that the number of station, transmission probability, the number of parallel beams and the number of frames in each A-MPDU are variables. When the PER is 10-2and the number of aggregated MPDUs in each A-MPDU is 20, it is identified that the MAC layer throughput of IEEE 802.11ac can be maximally attained up to a 92.8% of physical transmission rate. © 2014 Trans Tech Publications, Switzerland.
Choi D.-Y.,Yuhan University
Advanced Science Letters | Year: 2014
Handling fuzzy query in voice search on smartphones is one of the most difficult problems. It is mainly derived from the complexity and the degree of freedom of natural language. To reduce the complexity and the degree of freedom of fuzzy query in voice search on smarphones, attribute-driven approach for fuzzy query is proposed. In this paper, we design a prototype model for handling fuzzy query in voice search on smartphones. It is based on voice web search, user's physical location, search distance, search directory and user's search intentions. The filtering ratio on search results of the proposed approach compared to existing smartphones is presented. It is a further step towards location-based personalized voice search (LPVS) for smartphone users. © 2014 American Scientific Publishers All rights reserved.
Min H.,Bowling Green State University |
Min H.,Yuhan University
Benchmarking | Year: 2011
Purpose: To help fast-food restaurants enhance their competitiveness and then increase their market share, the purpose of this paper is to measure the service performances of fast-food restaurant franchises in the USA and identify salient factors influencing the service performances of fast-food restaurants over time. Design/methodology/approach: This paper develops a set of benchmarks that helps fast-food restaurants monitor their service-delivery process, identify relative weaknesses, and take corrective actions for continuous service improvements using analytic hierarchy process and competitive gap analysis. Findings: This study reveals that a service attribute considered most important to the fast-food restaurant customers' impressions of service quality is taste of food. This preference has not been changed over time. Also, we found a pattern of the correlation between the overall level of customer satisfaction with the fast-food restaurant and its word-of-mouth reputation. Furthermore, we discovered that the customers tended to be more favorable to easily accessible and national fast-food restaurant franchises than less accessible, relatively new, and regional counterparts. Research limitations/implications: The current study is limited to the evaluation of comparative service quality in the USA. Thus, this study may not capture the national differences in the restaurant customers' perceived service quality. Practical implications: For the last four decades, Americans' obsession with fast serving, cheap meals has made the fast-food restaurant a mainstay in their daily life. As the appetite for fast food grows, every corner of the American Society has been infiltrated by fast-food restaurants. With the increasing number of fast-food restaurants competing in the market, their survival often rests on their ability to sustain high-quality services and meet changing needs/preferences of customers. This paper provides practical guidelines for enhancing the competitiveness of the fast-food restaurant franchise. Originality/value: This paper is one of the first to compare the service quality of fast-food franchises in the USA and develop dynamic service quality standards for fast-food restaurant franchises using a longitudinal study. © Emerald Group Publishing Limited.
Min H.,Bowling Green State University |
Min H.,Yuhan University
Benchmarking | Year: 2013
Purpose: The purpose of this paper is to help fast-food restaurants successfully penetrate foreign markets and then strengthen their foothold in those markets by identifying cross-cultural differences in the perceived service quality of fast-food restaurants; and by examining how those differences affect the globalization of fast-food restaurant franchises based in the USA and Korea. Design/methodology/approach: This paper develops a set of target performance standards that helps fast-food restaurants monitor their service delivery process, identify relative weaknesses, and take corrective actions for continuous service improvements in cross-cultural settings using analytic hierarchy process and competitive gap analysis. Findings: This study reveals that a service attribute considered most important to the fast-food restaurant customers' impressions of service quality differs from one country (USA) to another (Korea). It was found that US customers valued taste of food most whereas Korean customers valued cleanliness most. Also, it was discovered that Koreans considered employee courtesy far more important for their service impression of service quality than Americans, while they were less concerned about food price than their US counterparts. Furthermore, Koreans tended to be more brand-conscious than Americans and thus considered word-of-mouth reputation more seriously than Americans for restaurant selection. Research limitations/implications: The current study is limited to the evaluation of comparative service quality of fast-food restaurants in only two countries (namely the USA and Korea). Thus, this study cannot be generalized to the restaurant customers' perceived service quality in other countries or cultural settings. Also, this paper focuses on the performance aspect of benchmarking rather than the strategic aspect of benchmarking. Practical implications: Saturated with the US restaurant market selling fast-serving and cheap meals, a growing number of US fast-food restaurant franchises began to explore foreign markets to increase world-wide customer bases. However, it is not easy for them to duplicate their domestic success in foreign soils due to different needs, tastes, and preferences of foreign customers. This paper helps the fast-food restaurant franchises develop viable market penetration and localization strategies and then provides practical guidelines for enhancing their competitiveness in the emerging foreign markets. Originality/value: This paper is one of the first to compare the service quality of fast-food franchises in the USA to that of Korean fast-food restaurant franchises from the cross-cultural perspectives. © Emerald Group Publishing Limited.
Park N.S.,Yuhan University |
Ko S.C.,Jeonju University
Journal of Mechanical Science and Technology | Year: 2011
Large eddy simulation (LES) of turbulent premixed flame stabilized by the bluff body is developed by using sub-grid scale combustion model based on the G-equation describing the flame front propagation. The basic idea of LES modeling is to evaluate the filtered-front speed, which should be enhanced in the grid scale by the scale fluctuations. The dynamic sub-grid scale models newly introduced into the G-equation are validated by the premixed combustion flow behind the triangle flame holder. The objective of this study is to investigate the validity of the dynamic sub-grid G-equation model to a complex turbulent premixed combustion such as bluff body stabilized turbulent premixed flames for realistic engineering application. A new turbulent flame speed model, introduced by the sub-grid turbulent diffusivity and the flame thickness, is also proposed and is compared with the usual model using sub-grid turbulent intensity and with the experimental data. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
Jeong K.,Yuhan University
ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning | Year: 2014
The heating ventilating and air conditioning system is changing rapidly from the traditional HVAC central supply system to the individual supply system with Electrical Heat Pump system (EHP) in Korean school buildings. The individual supply system has advantages to turn on and off individually and to adjust the thermal comfort separately, but energy is wasted in the unoccupied classroom when the last leaving occupant does not turn off the controller. If the controller is to be off automatically while the classroom is not in use, energy consumption would decrease dramatically. This project aims to cease the unnecessary EHP supply in a vacant classroom by inputting the class schedule from the central control room to reduce the energy-spending. Experimental measurements were carried out between the controlled classroom that is turned off when not in use and the uncontrolled room that is turned on continually. Occupant's comfort and energy consumption were measured and compared between the controlled case and the uncontrolled case. The energy consumption of controlled classroom case is 30-60% less than that of the non-controlled classroom case. This result shows that controlling the cooling supply for the unoccupied classroom using the class schedule can decrease the energy consumption remarkably. This supply control system can be used to conserve energy in school structures like universities.
Choi S.,Kyung Hee University |
Shin Y.,Yuhan University |
Park H.-K.,Kyung Hee University
Expert Systems with Applications | Year: 2011
This paper presents a new analysis method for aortic and mitral insufficiency murmurs using wavelet packet (WP) decomposition. We proposed four diagnostic features including the maximum peak frequency, the position index of the WP coefficient corresponding to the maximum peak frequency, and the ratios of the wavelet energy and entropy information to achieve greater accuracy for detection of heart murmurs. The proposed WP-based insufficiency murmur analysis method was validated by some case studies. We employed a thresholding scheme to discriminate between insufficiency murmurs and control sounds. Three hundred and thirty-two heart sounds with 126 control and 206 murmur cases were acquired from four healthy volunteers and 47 patients who suffered from heart defects. Control sounds were recorded by applying a wireless electric stethoscope system to subjects with no history of other heart complications. Insufficiency murmurs were grouped into two valvular heart defect categories, aortic and mitral. These murmur subjects had no other coexistent valvular defects. The proposed insufficiency murmur detection method yielded a high classification efficiency of 99.78% specificity and 99.43% sensitivity. © 2010 Elsevier Ltd. All rights reserved.
Lee H.C.,Yuhan University
Proceedings - 3rd International Conference on Advances in Mesh Networks, MESH 2010 | Year: 2010
This paper analyzes the effect of RTS (Request To Send) and CTS (Clear To Send) frames on the network performance in the ad hoc-based mobile LAN. An ad hocbased mobile LAN with two clients and one server is simulated using OPNET simulator to analyze network load, connection congestion window size and traffic received from each client in the FTP server. We found that both the connection congestion window size and network load about Clients are affected by the node mobility. The server terminates the FTP session with ClientA earlier if RTS/CTS is enabled. On the other hand, the server terminates the FTP session with ClientB later if RTS/CTS is enabled. We also identified that applying RTS/CTS scheme does not always improve the performance of the "traffic received from each client in the FTP server" in all network environments. © 2010 IEEE.
Yoon T.J.,Yuhan University |
Koppula S.,Konkuk University |
Lee K.H.,Konkuk University
Anti-Cancer Agents in Medicinal Chemistry | Year: 2013
Beta-glucans (β-glucans), naturally occurring polysaccharides, are present as constituents of the cell wall of cereal grains, mushrooms, algae, or microbes including bacteria, fungi, and yeast. Since Pillemer et al. first prepared and investigated zymosan in the 1940s and others followed with the investigation of β-glucans in the 1960s and 1970s, researchers have well established the significant role of β-glucans on the immune system relative to cancer treatment, infection immunity, and restoration of damaged bone marrow. However, information on their biological role in anti-metastatic activity remains limited. As an immunomodulating agent, β-glucan acts through the activation of innate immune cells such as macrophages, dendritic cells, granulocytes, and natural killer cells. This activation triggers the responses of adaptive immune cells such as CD4+ or CD8+ T cells and B cells, resulting in the inhibition of tumor growth and metastasis. Reports have shown that β-glucans exert multiple effects on cancer cells and cancer prevention. However the mechanisms of their actions appear complex due to differences in source, chemical structure, insufficiently defined preparation, and molecular weight, hence the inconsistent and often contradictory results obtained. This review is focused on the potential of β-glucans as anti-metastatic agents and the known mechanisms underlying their biological effects. © 2013 Bentham Science Publishers.
Lee H.-H.,University of Texas at Austin |
Chang E.,Yuhan University
Journal of Computer-Mediated Communication | Year: 2011
This study investigates consumer attitudes toward the online codesign process in mass customization among Korean consumers. The extended Technology Acceptance Model (TAM) was our theoretical framework, along with the constructs of perceived control and enjoyment. Web skill and fashion involvement were integrated as individual characteristics variables in the model. Data from 749 self-administered surveys collected in South Korea were used in this study. Findings indicated that TAM was an effective conceptual framework in explaining consumer response to the online codesign process. The statistically significant results of the perceived enjoyment and control constructs in the extended TAM suggest the importance of their addition to building a model to explain consumer attitudes toward the online codesign process. © 2011 International Communication Association.