• Journal of Internet Computing and Services
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• v.6 no.6
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• pp.23-34
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• 2005

In a large scale parallel computation, failures of some nodes or communication links end up with waste of computing resources, Several fault-tolerant MPI libraries have been proposed so far, but the programs written by using such libraries have a portability problem since fault-tolerant features are not supported by the MPI standard yet, In this paper, we propose an application-level fault-tolerant linear system solver that uses the asynchronous iteration algorithm and the standard MPI functions only, which does not have a portability problem and is more efficient by adopting a simplified recovery mechanism.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2192-2197
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• 2003

This paper suggests remote experiments using the internet for the control education. The remote experiment is composed of equipment server computers, networks accessible to internet, and real plants such as inverted pendulums, crane systems and microcontrollers. Additionally, it requires a server program that has I/O functions with plants and calculate the control, an interface program bridging between web and the server program, and the home page including the detail explanation for the usage. For effective educations, how to perform experiments and how to combine the experiment with lectures will be discussed. The simple experiments by entering a few control parameters and the complex experiments by designing overall controls, will be explained. Technologies related with the remote experiment and other possible remote experiment will be introduced. It is demonstrated that the remote experiment will be very useful, particular for control education where students have difficulties in performing the experiments for lack of experimental equipments.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.99-102
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• 2004

Caching is one of essential functions in a wireless internet proxy server cluster. To serve best quality of service and choose suitable a proxy server for user, load balancer have to consider cache cooperation between proxy servers. Usually hashing is a simple way to support cache cooperation. In this paper, we compare and analysis static hashing and MD 5 that can be used for cache cooperation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.6
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• pp.1433-1448
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• 2013

This study presents empirical evidence of the benefit of viewing narrative video clips on embedded virtual reality (VR) websites of hotels to relieve travel anxiety. As the effectiveness of using VR functions to relieve travel anxiety has been shown, we proposed that a VR website enhanced with narrative video clips could relieve travelers' anxiety about accommodations by showing the important aspects of a hotel. Thus, we created a website with a narrative video showing the escape route from a hotel room and another narrative video showing the surrounding neighborhood. We then conducted experiments by having human subjects explore the enhanced VR website and fill out a questionnaire. The results confirmed our hypothesis that there is a statistically significant relationship between relief from travel anxiety and the use of narrative videos on embedded VR websites of hotels.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3435-3454
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• 2016

Device-to-device (D2D) communication is a potential solution to the incessant increase in data traffic on cellular networks. The greatest problem is how to control the interference between D2D users and cellular mobile users, and between D2D users themselves. This paper proposes a solution for this issue by putting the full control privilege in cellular network using the software-defined networking (SDN) concept. A software virtual switch called Open vSwitch and several components are integrated into mobile devices for data forwarding and radio resource mapping, whereas the control functions are executed in the cellular network via a SDN controller. This allows the network to assign radio resources for D2D communication directly, thus reducing interference. This solution also brings out many benefits, including resource efficiency, energy saving, topology flexibility, etc. The advantages and disadvantages of this architecture are analyzed by both a mathematical method and a simple implementation. The result shows that implementation of this solution in the next generation of cellular networks is feasible.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.27-36
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• 2020

The popularization of smartphones allows people to instantly get the information that they want, through mobile apps, including financial services, movies and public transportation reservations, games and shopping. Furthermore, leisure activities through overseas travel are increasing due to the improvement of the living standards of people. These increases in overseas travel and the use of mobile apps lead to the increased use of mobile travel apps when booking tour packages. Although there are many studies on the usability assessment and user interface improvement for mobile apps, studies on the usability assessment for mobile travel apps are limited. We tested the usability for mobile travel apps to present some suggestions for improvements so that anyone can purchase travel packages easily and simply. We selected the top three mobile travel apps on Rankey.com that have different UIs. The heuristic method was used to evaluate usability. We present a better UI to allow users to use the app functions more easily by analyzing user interaction, ease of learning, readability, efficiency, and satisfaction for the entire use.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.3254-3272
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• 2017

With the development of wireless access technologies and the popularity of mobile intelligent terminals, cloud computing is expected to expand to mobile environments. Attribute-based encryption, widely applied in cloud computing, incurs massive computational cost during the encryption and decryption phases. The computational cost grows with the complexity of the access policy. This disadvantage becomes more serious for mobile devices because they have limited resources. To address this problem, we present an efficient verifiable outsourced scheme based on the bilinear group of prime order. The scheme is called the verifiable outsourced computation ciphertext-policy attribute-based encryption scheme (VOC-CP-ABE), and it provides a way to outsource intensive computing tasks during encryption and decryption phases to CSP without revealing the private information and leaves only marginal computation to the user. At the same time, the outsourced computation can be verified by two hash functions. Then, the formal security proofs of its (selective) CPA security and verifiability are provided. Finally, we discuss the performance of the proposed scheme with comparisons to several related works.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.840-855
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• 2011

In the context of additive noise steganography model, we propose a method to detect least significant bit (LSB) matching steganography in grayscale images. Images are decomposed into detail sub-bands with local linear transform (LLT) masks which are sensitive to embedding. Novel normalized characteristic function features weighted by a bank of band-pass filters are extracted from the detail sub-bands. A suboptimal feature set is searched by using a threshold selection algorithm. Extensive experiments are performed on four diverse uncompressed image databases. In comparison with other well-known feature sets, the proposed feature set performs the best under most circumstances.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.202-215
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• 2013

The generalization trend of smartphones has brought many smartphone games into daily lives. These games are mainly dependent on the interactions on the display of the phone using finger touches. On the other hand, functions for detecting the positions and actions of the phones such as gyro-sensors have been rapidly developed over the former orientation sensors and acceleration sensors. Though it has become technologically possible to detect the users' motion via the smartphone devices and to use the phone device directly as the game device, it is hard to find the actualized cases. This paper proposes a new paradigm that includes basic frameworks and algorithms for the games combining the motion tracking and mutual communications on the smartphones and presents the details of its implementation and results.

• Journal of Internet Computing and Services
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• v.21 no.3
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• pp.21-28
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• 2020

Fireworks Algorithm (FWA) is a relatively novel swarm-based metaheuristic algorithm for global optimization. To solve the low-efficient local searching problem and convergence of the FWA, this paper presents a Variable Amplitude Coefficient Fireworks Algorithm with Uniform Local Search Operator (namely VACUFWA). Firstly, the explosive amplitude is used to adjust improving the convergence speed dynamically. Secondly, Uniform Local Search (ULS) enhances exploitation capability of the FWA. Finally, the ULS and Variable Amplitude Coefficient operator are used in the VACUFWA. The comprehensive experiment carried out on 13 benchmark functions. Its results indicate that the performance of VACUFWA is significantly improved compared with the FWA, Differential Evolution, and Particle Swarm Optimization.