• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2338-2356
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• 2019

Vehicular ad-hoc network (VANET) is the name of technology, which uses 'mobile internet' to facilitate communication between vehicles. The aim is to ensure road safety and achieve secure communication. Therefore, the reliability of this type of networks is a serious concern. The reliability of VANET is dependent upon proper communication between vehicles within a given amount of time. Therefore a new formula is introduced, the terms of the new formula correspond 1 by 1 to a class special ST route (SRORT). The new formula terms are much lesser than the Inclusion-Exclusion principle. An algorithm for the Source-to-Terminal reliability was presented, the algorithm produced Source-to-Terminal reliability or computed a Source-to-Terminal reliability expression by calculating a class of special networks of the given network. Since the architecture of this class of networks which need to be computed was comparatively trivial, the performance of the new algorithm was superior to the Inclusion-Exclusion principle. Also, we introduce a mobility metric called universal speed factor (USF) which is the extension of the existing speed factor, that suppose same speed of all vehicles at every time. The USF describes an exact relation between the relative speed of consecutive vehicles and the headway distance. The connectivity of vehicles in different mobile situations is analyzed using USF i.e., slow mobility connectivity, static connectivity, and high mobility connectivity. It is observed that $p_c$ probability of connectivity is directly proportional to the mean speed ${\mu}_{\nu}$ till specified threshold ${\mu}_{\tau}$, and decreases after ${\mu}_{\tau}$. Finally, the congested network is connected strongly as compared to the sparse network as shown in the simulation results.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.29-33
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• 2001

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4372-4388
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• 2014

Robotic sensor network (RSN) contains mobile sensors and robots providing feasible solution for many multi-agent applications. One of the most critical issues in RSN and its application is how to effectively assign tasks. This paper presents a novel connectivity preserving hybrid task allocation strategy to answer the question particularly for RSN. Firstly, we model the task allocation in RSN to distinguish the discovering and allocating processes. Secondly, a fully distributed simple Task-oriented Unoccupied Neighbor Algorithm, named TUNA, is developed to allocate tasks with only partial view of the network topology. A connectivity controller is finally developed and integrated into the strategy to guarantee the global connectivity of entire RSN, which is critical to most RSN applications. The correctness, efficiency and scalability of TUNA are proved with both theoretical analysis and experimental simulations. The evaluation results show that TUNA can effectively assign tasks to mobile robots with the requirements of only a few messages and small movements of mobile agents.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3335-3356
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• 2015

In this paper, we analyze the connectivity of cognitive radio ad-hoc networks in a log-normal shadow fading environment. Considering secondary user and primary user's locations and primary user's active state are randomly distributed according to a homogeneous Poisson process and taking into account the spectrum sensing efficiency of secondary user, we derive mathematical models to investigate the connectivity of cognitive radio ad-hoc networks in three aspects and compare with the connectivity of ad-hoc networks. First, from the viewpoint of a secondary user, we study the communication probability of that secondary user. Second, we examine the possibility that two secondary users can establish a direct communication link between them. Finally, we extend to the case of finding the probability that two arbitrary secondary users can communicate via multi-hop path. We verify the correctness of our analytical approach by comparing with simulations. The numerical results show that in cognitive radio ad-hoc networks, high fading variance helps to remarkably improve connectivity behavior in the same condition of secondary user's density and primary user's average active rate. Furthermore, the impact of shadowing on wireless connection probability dominates that of primary user's average active rate. Finally, the spectrum sensing efficiency of secondary user significantly impacts the connectivity features. The analysis in this paper provides an efficient way for system designers to characterize and optimize the connectivity of cognitive radio ad-hoc networks in practical wireless environment.

• International Journal of Knowledge Content Development & Technology
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• v.11 no.1
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• pp.29-48
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• 2021

The paper discusses the ICT infrastructure as far as the availability of (computers, local or wide area networks, Internet connectivity and its reliability, size of the bandwidth and its optimization, etc.) in the S&T research institution. It also examined the profile of the research scientists and looked at the type of ICT infrastructure that is available for their use as well as the reliability of the Internet connectivity within these research institutions. It looked at the broadband capacities of the research institutions and the ICT capabilities in respect of the technical and managerial support back-up that are available to the research institutions. The study used the survey research method with a questionnaire as well as personal observation to gather the data. From the data gathered, it was realized that the internet connectivity and the size of the bandwidth that the R&D institutions subscribed to differed significantly. Again, the extent to which the research scientists were able to access the internet in their respective institutions depended on the quality of the local network in place. Generally, the investments in ICT were made for different management objectives, and these were meant to facilitate the generation of new knowledge as well as make measurable improvements in R&D activities.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3572-3593
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• 2015

This article investigates the topology control problem in the space information network (SIN) using a hierarchical autonomous system (AS) approach. We propose an AS network topology control (AS-TC) algorithm to minimize the time delay in the SIN. Compared with most existing approaches for SIN where either the purely centralized or the purely distributed control method is adopted, the proposed algorithm is a hybrid control method. In order to reduce the cost of control, the control message exchange is constrained among neighboring sub-AS networks. We prove that the proposed algorithm achieve logical k-connectivity on the condition that the original physical topology is k-connectivity. Simulation results validate the theoretic analysis and effectiveness of the AS-TC algorithm.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.25-30
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• 2022

Since Tim Berners-Lee introduced the idea of the web to the world in the late 1980s, the way information is produced, accessed and used has been constantly changing. This was once again an era of upheaval after Apple's Steve Jobs introduced the smartphone to the world in the mid-2000s. Before the advent of smart devices, web browsing was mainly done using desktops. After the advent of this device, the era of solving almost all human needs with a small PC in the palm of your hand has arrived. The necessity of seamless connectivity between devices, which are constantly emerging and evolving, asks our attention more than ever. In this study, we will discuss a case of design and development of a national open access website, which is optimized for dynamic online user behaviors with diverse devices. Our goal is to provide one true web for people to use in their environment. Device makers need to provide products identical to the desktop environment as much as possible. Service providers should also provide services optimized for each device in hyper-connected environments. Providing a web, optimized for user's online context, will eventually result in a sustainable user experience.

• International journal of advanced smart convergence
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• v.8 no.4
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• pp.179-187
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• 2019

Vehicular density is usually low in a highway environment. Consequently, connectivity of the vehicular ad hoc networks (VANETs) might be poor. We are investigating the problem of deploying the approximation optimal roadside units (RSUs) on the highway covered by VANETs, which employs VANETs to provide excellent connectivity. The goal is to estimate the minimal number of deployed RSUs to guarantee the connectivity probability of the VANET within a given threshold considering that RSUs are to be allocated equidistantly. We apply an approximation algorithm to distribute RSUs locations in the VANETs. Thereafter, performance of the proposed scheme is evaluated by calculating the connectivity probability of the VANET. The simulation results show that there is the threshold value M of implemented RSUs corresponding to each vehicular network with N vehicles. The connectivity probability increases slowly with the number of RSUs getting larger.

• Journal of Korean Institute of Industrial Engineers
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• v.32 no.2
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• pp.82-90
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• 2006

Reconfigurability of machine tools is one of the critical factors to realize the responsive manufacturing systems to satisfy the mass customization production. This paper presents the methods to model the reconfigurable machine tools (RMTs) on Internet in response to change in the machining requirements. Specifically, the structure and motion model of machine tools using module combination rules and connectivity graph are developed. And we developed Internet-based simulator for designing of RMTs (ISD-RMT). In response to the user requirements, various structures of RMTs can be derived using the module combination rules and connectivity graph relationships. In addition, the user can verify generating structures through the control and simulation procedures.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.1-6
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• 2016

The Internet of Things (IoT) is a new technology paradigm demanding one packaged system of various semiconductor and MEMS devices. Therefore, the development of electronic packaging technology with very high connectivity is essential for successful IoT applications. This paper discusses both fan-out wafer level packaging (FOWLP) and 3D stacking technologies to achieve the integrattion of heterogeneous devices for IoT. FOWLP has great advantages of high I/O density, high integration, and design flexibility, but ultra-fine pitch redistribution layer (RDL) and molding processes still remain as main challenges to resolve. 3D stacking is an emerging technology solving conventional packaging limits such as size, performance, cost, and scalability. Among various 3D stacking sequences wafer level via after bonding method will provide the highest connectivity with low cost. In addition substrates with ultra-thin thickness, ultra-fine pitch line/space, and low cost are required to improve system performance. The key substrate technologies are embedded trace, passive, and active substrates or ultra-thin coreless substrates.