• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.153-162
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• 1992

A mathematical model for a long range water supply planning is developed as a dynamic capacitated facility location problem, in which operating costs and two types of fixed costs are considered. The fixed costs are for water supply systems such as dams and reservoirs and for water conveyance systems of waterways or conduits from each water supply points. A spreadsheet model is developed to support the efficiency of user interface and to implement a heuristic solution procedure. The proposed solution procedure utilizes SOLVER tool and it has been applied to a system with fictitious data but with reality and applicability in mind. As a result of the mathematical analysis, not only the most economic construction timings of surface water facilities and distribution systems but also the most economical water supply operating patterns are identified.

• Journal of Drive and Control
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• v.9 no.4
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• pp.19-25
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• 2012

This paper explains how eliminating contamination from the manufacturing processes will lead to better product quality and hence the need for reworking, a trouble free commissioning period and greatly improved production efficiency. All of these will reduce costs and energy usage. It will also ensure that the product is delivered to the customer in a condition that will ensure improved reliability and longer life, again reducing both energy and other operating costs. Correctly designing the contamination control measures will achieve and maintain the level of fluid cleanliness that is required by the end user. The filter is critical to cleanliness management and should be selected with the same degree of thought and consideration as for other major components. This paper explains the role that Cleanliness Management plays in the reducing the carbon footprint of systems and processes by making them perform more efficiently for longer periods. It also examines two differing ways of selecting filters to incorporate the features of newer designs, and shows how significant savings in the costs of ownership can be achieved using these approaches.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.171-174
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• 2003

Shortest path problems are among the most studied network flow optimization problems, with interesting applications in various fields. One such field is the route determination service, where various kinds of shortest path problems need to be solved in location-based service. Our research aim is to propose a route technique in real-time location-based service (LBS) environments according to user's route preferences such as shortest, fastest, easiest and so on. Turn costs modeling and computation are important procedures in route planning. We propose a new rest modeling method for turn costs which are traditionally attached to edges in a graph. Our proposed route determination technique also has an advantage that can provide service interoperability by implementing XML web service for the OpenLS route determination service specification.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1249-1265
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• 2022

Video streaming has become one of the most popular applications for mobile devices. The network bandwidth required for video streaming continues to exponentially increase as video quality increases and the user base grows. Multi-Path TCP (MPTCP), which allows devices to communicate simultaneously through multiple network interfaces, is one of the solutions for providing robust and reliable streaming of such high-definition video. However, mobile video streaming over MPTCP raises new concerns, e.g., power consumption and cellular data usage, since mobile device resources are constrained, and users prefer to minimize such costs. In this work, we propose a mobile video streaming framework over MPTCP (mDASH) to reduce the costs of energy and cellular data usage while preserving feasible streaming quality. Our evaluation results show that by utilizing knowledge about video behavior, mDASH can reduce energy consumption by up to around 20%, and cellular usage by 15% points, with minimal quality degradation.

• The Journal of the Korea Contents Association
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• v.14 no.11
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• pp.533-540
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• 2014

As for the application system or the user authentication scheme that is used in the system, various technologies including simple ID/PW, certificate, fingerprint/iris, phone, security card, and OTP are being used. But simple ID/PW and phone certification lack security features. As for the certificate, fingerprint/iris, and security card/OTP, the weakness in security has been quite strengthened, but there are costs and complexity involved to use these. This paper proposes a new measure of much safer and low-cost user authentication that improves the security level and uses mobile external storage media such as USB that people commonly have.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.6169-6187
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• 2017

With the fast growth of mobile services, Mobile Cloud Computing(MCC) has gained a great deal of attention from researchers in the academic and industrial field. User authentication and privacy are significant issues in MCC environment. Recently, Tsai and Lo proposed a privacy-aware authentication scheme for distributed MCC services, which claimed to support mutual authentication and user anonymity. However, Irshad et.al. pointed out this scheme cannot achieve desired security goals and improved it. Unfortunately, this paper shall show that security features of Irshad et.al.'s scheme are achieved at the price of multiple time-consuming operations, such as three bilinear pairing operations, one map-to-point hash function operation, etc. Besides, it still suffers from two minor design flaws, including incapability of achieving three-factor security and no user revocation and re-registration. To address these issues, an enhanced and provably secure authentication scheme for distributed MCC services will be designed in this work. The proposed scheme can meet all desirable security requirements and is able to resist against various kinds of attacks. Moreover, compared with previously proposed schemes, the proposed scheme provides more security features while achieving lower computation and communication costs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.713-720
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• 2010

Lately, IPTV is in the limelight using a broadband information service to provide video content and broadcast services. Current IPTV system is combining CAS and DRM system for VOD contents to protect transmitting contents and authentication, but it has drawbacks such as system's complexity and high construction costs. Multicast DRM system emerged as a method to improve them, but, in the multicast DRM system, if the key is intercepted by a malicious user, it can be viewed by an unauthorized user of illegal broadcasting which can be a problem. In this paper, we suggest to protect content from a malicious user by applying the techniques using user authentication in the multicast DRM system.

• The Journal of Information Systems
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• v.18 no.2
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• pp.1-18
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• 2009

Recently, internet banking is growing rapidly. Moot banks in Korea provide internet banking services. Internet banking becomes a major trend in the financial marketplace. With advanced computer technology and declining communication costs, many customers prefer online alternatives such as internet banking, mobile banking or phone banking rather than going to banks by themselves. The number of customers using those alternatives is skyrocketing and domestic commercial banks encourage them of the use. As the internet is highly developed, customers demand higher quality services and banks develop and provide diverse services in order to respond to them. However, internet banking service users are still afraid of their personal and financial information being exposed on the internet. The purpose of this research is to empirically analyze the influence that appropriate internet banking affect user's security intention. The research model proposed in this study includes user's security intention which is influenced by self-efficacy, security trust, Internet banking attitude, perceived security and security intention. According to the result of this study, self-efficacy and security trust are related to the security attitude. There is a significant relationship between security attitude and perceived security. Also, user's security attitude and perceived security is significantly affected by security intention.

• The Journal of the Korea Contents Association
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• v.19 no.7
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• pp.421-426
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• 2019

Nowadays, various type of technologies are used for user authentication, such as knowledge based(ID/PW, etc.) authentication, biometric based(Iris/fingerprint/vein recognition) authentication, ownership based(OTP, security card, etc.) authentication. ID/PW authentication technology, a knowledge based authentication, despite the advantages of low in implementation and maintenance costs and being familiar to users, there are disadvantages of vulnerable to hacking attacks, Other authentication methods solve the vulnerability in ID/PW authentication technology, but they have high initial investment cost and maintenance cost and troublesome problem of reissuance. In this paper, we proposed to improve security and convenience over existing ID/PW based authentication technology, and to secure user authentication without restriction on the devices used for authentication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2490-2506
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• 2022

In Mobile Edge Computing (MEC), attackers can speculate and mine sensitive user information by eavesdropping wireless channel status and offloading usage pattern, leading to user privacy leakage. To solve this problem, this paper proposes a Privacy-preserving and Energy-efficient Offloading Algorithm (PEOA) based on Lyapunov optimization. In this method, a continuous Markov process offloading model with a buffer queue strategy is built first. Then the amount of privacy of offloading usage pattern in wireless channel is defined. Finally, by introducing the Lyapunov optimization, the problem of minimum average energy consumption in continuous state transition process with privacy constraints in the infinite time domain is transformed into the minimum value problem of each timeslot, which reduces the complexity of algorithms and helps obtain the optimal solution while maintaining low energy consumption. The experimental results show that, compared with other methods, PEOA can maintain the amount of privacy accumulation in the system near zero, while sustaining low average energy consumption costs. This makes it difficult for attackers to infer sensitive user information through offloading usage patterns, thus effectively protecting user privacy and safety.