• The Journal of the Convergence on Culture Technology
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• v.7 no.2
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• pp.377-388
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• 2021

With the growth of the global sharing economy market, various sharing services have recently appeared in South Korea. Seoul city unmanned public bicycle rental service, "Ttareuni" is one of the services representing the shared mobility industry in South Korea. Although many users use this service, the usability of the mobile application, which is the essential medium of utilizing the service, is not improving. In this regard, this study conducted usability testing and in-depth interviews for Ttareungi's main users in their 20s and 30s to improve the user experience of the mobile application of Ttareungi. As a result, the problems of Ttareungi mobile application were identified, and based on this, design considerations for shared mobility services having publicity like Ttareungi were proposed. This is expected to contribute to improving the user experience of shared mobility services.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.19-32
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• 2009

In this paper, we design thin-client framework capable of application sharing & data access on the Internet, and apply related skills, such as X windows system, pseudo server, CODA file system, MPI(Message Passing Interface). We suggest a framework for the thin client to access data produced by working on a server optimally as well as to run server side application, even in the case of network down. Additionally, it needed to reflect all local computing changes to remote server when network is restored. To design thin client framework with these characteristics, in this paper, we apply distributed pseudo server and CODA file system to our framework, also utilize MPI for the purpose of more efficient computing & management. It allows for implementation of network independent computing environment of thin client, also provide scalable application service to numerous user through the elimination of bottleneck on caused by server overload. In this paper, we discuss the implementing method of thin client framework in detail.

• Journal of Power Electronics
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• v.14 no.2
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• pp.351-361
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• 2014

The discrete torque generation mechanism and inherently nonlinear magnetic characterization of switched reluctance motors lead to unacceptable torque ripples and limit the application of these motors. In this study, a phase current profiling technique and torque sharing function are proposed in consideration of magnetic saturation effects and by minimizing power loss in the commutation area between the adjacent phases. Constant torque trajectories are considered in incoming and outgoing phase current planes based on nonlinear T-i-theta curves obtained from experimental measurements. Optimum points on constant torque trajectories are selected by improving drive efficiency and minimizing copper loss in each rotor position. A novel analytic invertible function is introduced to express phase torque based on rotor position and its corresponding phase current. The optimization problem is solved by the proposed torque function, and optimum torque sharing functions are derived. A modification method is also introduced to enhance the torque ripple-free region based on simple logic rules. Compared with conventional torque sharing functions, the resultant reference current from the proposed method has less peak and effective values and exhibits lower copper loss. Experimental and simulation results from a four-phase 4 KW 8/6 SRM validate the effectiveness of the proposed method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3377-3395
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• 2015

Recently, several approaches to share road conditions and/or digital contents through VANETs have been proposed, and such approaches have generally considered the radial distance from the information source as well as the TTL to provision an ephemeral, geographically-limited information sharing service. However, they implement general MANETs and have not been tailored to the constrained movement of vehicles on roads that are mostly linear. In this paper, we propose a novel application-level mechanism that can be used to share road conditions, including accidents, detours and congestion, through a VANET. We assign probabilities to roads around each of the intersections in the neighborhood road network. We then use the graph representation of the road network to build a spanning tree of roads with the information source as the root node. Nodes below the root represent junctions, and the edges represent inter-connecting road segments. Messages propagate along the branches of the tree, and as the information propagates down the branches, the probability of replication decreases. The information is replicated until a threshold probability has been reached, and our method also ensures that messages are not delivered to irrelevant vehicles, independently of their proximity to the source. We evaluated the success rate and performance of this approach using NS-3 simulations, and we used IDM car following and MOBIL lane change models to provide realistic modeling of the vehicle mobility.

• Journal of the Korea Society of Computer and Information
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• v.23 no.10
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• pp.73-80
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• 2018

The shared economy began with the concept of sharing the physical and intellectual assets of individuals with others. Nowadays, the concept of shared economy is becoming one of the industries as an enterprise type. Especially, with the development of the Internet and smart devices, various forms of shared economy have been developed in accordance with the need of sharing of individual income. Digital content is also a shareable commodity and it is seeking to utilize it as an item of shared economy. Accordingly, when digital contents are used as a shared economy, there are various possible threats -security threats that may arise in the course of transactions, potential for theft, alteration and hacking of contents. In this paper, we propose transaction method and content protection method using block chain-ethereum technology to reduce security threats and transparent transactions that can occur in digital contents transactions. Through the proposed method, the trust of the consumer and the supplier can be measured and the encryption can be performed considering the characteristics of the data to be traded. Through this paper, it is possible to increase the transparency of smart transaction of digital contents and to reduce the risk of content distortion, hacking, etc.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.587-592
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• 2007

This paper explains the design and implementation of the EC_NH. EC_NH is a system that is suitable for detecting, sharing and recovering software error based on multimedia CSCW(Computer Supportes Cooperated Work). With error sharing system, a group cooperating users can share error applications. From the perspective of multimedia collaborative environment, an error application becomes another interactive presentation error is shared with participants engaged in a cooperative work. Our Digital Carousel enables user to share media objects through media synchronization mechanism. We implemented the Digital Carousel so that the users participated in collaborative work may refer shared media or error objects as the same view to others.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.188-194
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• 2020

This paper presents a high-efficiency Switch Mode Line Transformer (SMLT) composed of load-shared dual modules, which is based on the AC/AC LLC resonant converter. Given that the conventional adaptor is usually composed of two power stages, namely, the PFC and DC/DC converters, its system size can be increased according to the output power. However, given that the proposed SMLT can separate the PFC converter from the adaptor, the size reduction of the system can be achieved. Meanwhile, the SMLT with a single module has the limit of the size reduction because of a high resonant current. Thus, it can be configured with dual or multiple modules to reduce the resonant current. Then, their load sharing can be guaranteed by only the proposed transformer structure without an extra current controller. The validity of the proposed converter is proven through a 850-W prototype.

• Journal of Power Electronics
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• v.15 no.2
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• pp.327-337
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• 2015

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.

• International Journal of Knowledge Content Development & Technology
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• v.9 no.2
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• pp.33-44
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• 2019

This paper discussed the factors that necessitated information networking, types of networks, benefits of information networking, library information networking and the University of Port 0Harcourt library network initiatives. Information networking is a process of communication, exchange of ideas, resource sharing and collaboration between individuals, organizations, institutions and libraries and it is facilitated by ICTs and the internet for improved accessibility. It has been brought about by information explosion, rapid advancement in information communication technologies, inadequate funding and increased demand for quality information. Networks can be classified into local, national, regional, and international networks and are formed to serve different categories of user communities. Benefits of information networking include resource sharing, on-line conferences and participation in programmes at distant centers, collaboration among scholars in different countries. Communication flow through the internet, social media, and electronic mail. Library information networking started with the interlibrary loan which has metamorphosed into library consortia in which groups of libraries partner to coordinate activities, share resources and combine expertise. The University of Port Harcourt Library network initiatives started with an e-granary (a CD ROM) and the establishment of a local area network. The library subscribes to more than 10 electronic databases. Information networking has greatly improved the sharing of resources in acquisition and dissemination of information resources since no single institution can acquire the overwhelming number of information resources in their various formats.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.205-212
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• 2019

With the rapid spread of mobile phones, users are continuously interested in using the mobile phone in connection with personal activities. Also, increasingly users want to share (transmit and receive) and save data more easily and simply in the mobile environment. This paper suggests motion recognition of mobile phone to share personal information with any people located within a certain distance using location-based service with GCM service. The suggested application is based on Google Cloud Messaging which enables asynchronous communication with the mobile applications executed in Android operating system. The requirements of light-weight mechanism can be satisfied as it is possible to access sharing of personal information easily, simply and in real time through all mobile devices anywhere.