• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.822-828
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• 2005

Customer satisfaction becomes one of the important managerial concerns associated with corporate competency in current competitive environment for Internet communication service companies. Hence, it is demanding to improve a company's customer satisfaction through the total quality management perspective. In practice, engineers as well as the management hope to find major quality characteristics with Internet communication network that is closely related to customer satisfaction, consequently aiming to the raise of their company's customer satisfaction. This paper presents an empirical relationship analysis between network quality characteristics and customer satisfaction on Internet communication. Methodologically, the relationship analysis framework is based on the regression variable selection procedures. In this framework, it is implemented that; 1) iterative model building; and 2) consistent criteria application to statistical tests for selecting significant variables. A case study shows that; 1) the customer satisfaction on the network connection seems to be more closely related to the network quality characteristics compared with the customer satisfaction on the network speed; and 2) the download disconnection rate has relatively evident relationship with the customer satisfaction on the network connection.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.1
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• pp.44-54
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• 2007

In the military field, according to the MIL-STD-188-220, which is an Ad-Hoc communication protocol used for sending out or receiving data and voice smoothly among nodes in the situation that wireless communication nodes move arbitrarily, data communication is cut off because nodes can not know topology changes perpetually in the link disconnection state due to node movement in the case that transmitters do not confirm whether data is delivered to receivers or not, and transmit only the data having routine precedence continuously. In order to solve this problem, we have proposed the technique that makes efficient data communication possible by achieving a rapid topology change detection and link information update using TEST frame. We have analyzed TEST frame application effects in the two aspects of the topology update delay time and the data transmission success ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1373-1378
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• 2017

This paper presents a basic ECU(Electronic Control Unit) hardware development procedure for the functional safety of in-vehicle network systems. We consider complete hardware redundancy as a safety mechanism for in-vehicle communication network under the assumption of the wired network failure such as disconnection of a CAN bus. An ESC (Electronic Stability Control) system is selected as an item and the required ASIL(Automotive Safety Integrity Level) for this item is assigned by performing the HARA(Hazard Analysis and Risk Assessment). The basic hardware architecture of the ESC system is designed with a microcontroller, passive components, and communication transceivers. The required ASIL for ESC system is shown to be satisfied with the designed safety mechanism by calculation of hardware architecture metrics such as the SPFM(Single Point Fault Metric) and the LFM(Latent Fault Metric).

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2278-2288
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• 2017

Multilevel converter topologies are widely used in many applications. The cascaded H-bridge multilevel inverter (CHBMI), which is one of many multilevel converter topologies, has been introduced as a useful topology in high and medium power. However, it has a drawback to require a lot of switches. Therefore, the reliability of CHBMI is important factor for analyzing the performance. This paper presents a simple switch fault diagnosis method for single-phase CHBMI. There are two types of switch faults: open-fault and short-fault. In the open-fault, the body diode of faulty switch provides a freewheeling current path. However, when the short-fault occurs, the distortion of output current is different from that of the open-fault because it has an unavailable freewheeling current flow path due to a disconnection of fuse. The fault diagnosis method is based on the zero current time analysis according to zero-voltage switching states. Using the proposed method, it is possible to detect the location of faulty switch accurately. The PSIM simulation and experimental results show the effectiveness of proposed switch fault diagnosis method.

• Journal of Korean Library and Information Science Society
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• v.37 no.3
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• pp.193-208
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• 2006

The customer satisfaction. which is close with the loyalty, rate of disconnection and re-purchase and the new customer creation is important in point of the enterprise performance measurement system. There have been a number of studies that applied different models in other to assess the customer satisfaction of public and non-public area. But the general evaluation models which are existing can't consider the discrimination characteristic of different types of products or services. And these models didn't reflect the quality of the Internet environment of the public library service which appears newly. This study delved into literature of library service and customer satisfaction evaluation and suggest the classification system of public library service and the evaluation model of customer satisfaction for public library.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1054-1060
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• 2013

This paper proposes a vehicle ad-hoc network (VANET) routing algorithm to reduce the probability of routing path discontinuity in urban intersections. In urban intersections, the vehicles may frequently change their moving directions. It can cause the disconnection of routing path and the increase of a packet transmission delay. In order to resolve this problem, the proposed routing algorithm exploits the information of moving directions in urban intersections. In this way, the proposed algorithm can reduce the probability of the local maximum which causes the increase of the number of routing hops and packet transmission delay. Simulation results show that the proposed algorithm can reduce the local maximum probability by 10% and increase the successful packet transmission ratio by 5% compared to the conventional VANET routing algorithms.

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2969-2979
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• 2000

A mobile host has failure causes such as failure of the mobile host, disconnection of the mobile host, and wireless link failure that have not been seen in traditional computing environments. So far there have been few studies on fault tolerance of a mobile host in mobile computing environments. The Lazy scheme, a failure recovery technique of the mobile host, is a cost-effective one. However, this scheme has a defect that the mobile host cannot be recovered from failure of the base station with acheckpoint of the mobile host. In this paper, we propose and evaluate the Redundant Lazy scheme for performance improvement of the Lazy scheme.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.101-111
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• 2004

As different from wired internet, wireless internet has limitations due to the following characteristics; low bandwidth, frequent disconnection, low computing power, small screen in user terminal, and user mobility. Also, wireless internet server should be scalable to handle a large scale traffic due to rapidly growing users. Wireless proxy servers are used for the wireless internet because their caching and transcoding functions are helpful to overcome the above limitation. TranSend was proposed as a clustering based wireless proxy server but its scalability is difficult to achieve because there is no systematic way to do it. In this Paper. we proposed a clustering based wireless internet proxy server which can be scalable in a systematic way. We performed experiments using 16 PCs and experimental results show 32.17% performance improvement of the proposed system compared to TranSend system.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.19-23
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• 2012

This thesis is the result of conducting an analysis to find the solution to the phenomenon of power stoppage due to the disconnection of a CT (Current Transformer) because of vibration. The CT which measures the most essential current is used in power industries as part of a generator protection relay. When it comes to the bottom plate of a CT, nonconductor; such as bakelite and laminates; these material elements should be used because it is impossible to utilize the conductor when measuring the current of a generator which carries a high current if you use other materials. These nonconductor's material properties are irregular and interpretation errors often occur because the weight is light. In addition, since the change of dynamic characteristics which are related to the temperature often occur, it is important to match the real situation by considering an error of interpretation rather than selecting the quality of the material. Lastly, the conclusion that the study drew is that it is possible to avoid the resonance by utilizing three changes to the components to solve the problem concerning the high vibration which is caused by non-conductive objects. These changes are the most crucial points in this thesis: First, material changes to the Plate. Second, weight changes to the Coil. Third, thickness changes to the Plate.

• The Journal of Industrial Distribution & Business
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• v.10 no.1
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• pp.19-27
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• 2019

Purpose - The purpose of the paper is to examine disconnection between supply and demand shipping market, which means shipowner has determined to raise capacity in bust period. Research design, data, and methodology - The research method to be applied is first to look into conceptual theory about shipping market, and then to study imbalance of supply and demand situations in shipping on crisis, and next, to analyses paradoxical aspects traced. Results - Shipping market is a volatile and cyclic characteristics, and its situations have to be examined very carefully. Since financial crisis has broken up in 2008, it is natural to think that world trade volumes has reduced rapidly, which means demand for shipping service has fallen, and accordingly, tonnage should be stagnated as well. However, shipping companies have put capacity into market as unexpectedly. This is because of economy of scale and time lag. Here, this can be explained in terms of paradox that is proved in this paper. Conclusions - From careful research in this paper, it is found that supply and demand are not always got along with market situations, in other words supply side could be working well, in spite of depression time of demand situations in world shipping markets.