• KIPS Transactions on Software and Data Engineering
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• v.6 no.3
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• pp.141-148
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• 2017

The current advancement of mobile devices enables users to collect a sequence of user positions by use of the positioning technology and thus the related research regarding positioning or location information are quite arising. An individual mobility model based on positioning data and time data are already established while group mobility model is not done yet. In this research, group mobility model, an extension of individual mobility model, and the process of establishment of group mobility model will be studied. Based on the previous research of group mobility model from two individual mobility model, a group mobility model with more than two individual model has been established and the transition pattern of the model is represented by Markov chain. In consideration of real application, the computing time to establish group mobility mode from huge positioning data has been drastically improved by use of GPGPU comparing to the use of traditional multicore systems.

• KIISE Transactions on Computing Practices
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• v.22 no.7
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• pp.320-325
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• 2016

By developing the IoT(Internet of Things) technology, devices for smart home environment have rapidly increased. With respect to mobiles, these applications are used to control and manage the various smart devices effectively. However, the existing mechanisms only provide simple information, and hence a difficulty to search or control the smart devices persists, since there is no meaningful relationship between them. In this research, we suggest an interface which visualizes the device's data and controls them effectively, based on the user's device using pattern. As a solution for this problem, we classify the user pattern based on a timeline for the associated circumstance, and visualize the device's data to make a group or to control individually in an easier approach. Also, all meaningful information could be confirmed by summarizing all the data of smart devices.

• Journal of the HCI Society of Korea
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• v.1 no.1
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• pp.29-36
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• 2006

Tactile displays can provide useful information without disturbing others and are particularly useful for people with visual or auditory impairments. They can also complement other displays. In this paper, we present a new vibrotactile display device for wearable, mobile, and ubiquitous computing environments. The proposed vibrotactile device has a $5{\times}5$ array configuration for displaying complex information such as letters, numbers, and haptic patterns as well as simple directional ques and situation awareness alarms. Commercially available coin-type vibration motors are embedded vertically in flexible mounting pads in order to best localize vibrations on the skin. An embedded microprocessor controls the motors sequentially with an advanced tracing mode to increase recognition rate. User studies with the vibrotactile device on the top of the foot show 86.7% recognition rate for alphabet characters after some training. In addition, applying vibrotactile device to driving situation shows 83.9% recognition rate. We also propose some potentially useful application scenarios including Caller Identification for mobile phones and Navigation Aids for GPS systems while driving.

• The KIPS Transactions:PartD
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• v.14D no.7
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• pp.719-726
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• 2007

Recently, NAND flash memory has been used for a storage device in various mobile computing devices such as MP3 players, mobile phones and laptops because of its shock-resistant, low-power consumption, and none-volatile properties. However, due to the very distinct characteristics of flash memory, disk based systems and applications may result in severe performance degradation when directly adopting them on flash memory storage systems. Especially, when a B-tree is constructed, intensive overwrite operations may be caused by record inserting, deleting, and its reorganizing, This could result in severe performance degradation on NAND flash memory. In this paper, we propose an efficient buffer management scheme, called IBSF, which eliminates redundant index units in the index buffer and then delays the time that the index buffer is filled up. Consequently, IBSF significantly reduces the number of write operations to a flash memory when constructing a B-tree. We also show that IBSF yields a better performance on a flash memory by comparing it to the related technique called BFTL through various experiments.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.4
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• pp.328-336
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• 2004

Recently a mobile service is changing into a system environment that offers the customer various contents service. Representative example of service is a Calling Identity Del ivory Service(CID). Such service has the problem in the case which the receiver cannot remember the phone number of the sender; it has a difficult problem that cannot easily confirm whose the phone number it is. Therefore, it is desirable to design and implement visual services that can enhance the recognition of users. In this paper, we propose the architecture that is similar to a Calling Identity Delivery Service. We propose the architecture for communication service and system that is able to visually display the information of the sender using 2D image data in mobile environment. After that we set the image information to represent the user and this method is able to visually display the information of the sender by transmitting an image data through channels from switch station or base station using the server. When the receiver receives a phone call from the sender, this method provides an efficient service by transmitting visual data with bell sound. That is, the image information of sender is appeared on liquid crystal display(LCD) of the receiver at the same time. We investigate the concepts for processing real-time transmission of image data and describe an example of the implementation result that is based on system. This technology has a potential influence on the marketing and presents an efficiency of this method.

• Journal of KIISE:Databases
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• v.33 no.1
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• pp.86-101
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• 2006

The bandwidth of channel and the power of the mobile devices are limited on a wireless environment. In this case, data broadcast has become an excellent technique for efficient data dissemination. A significant amount of researches have been done on generating an efficient broadcast program of a set of data items with different access frequencies over multiple wireless broadcast channels as well as single wireless broadcast channel. In this paper, an efficient data allocation method over multiple wireless broadcasting channels is explored. In the traditional approaches, a set of data items are partitioned into a number of channel based on their access probabilities. However, these approaches ignore a variation of access probabilities of data items allocated in each channel. In practice, it is difficult to have many broadcast channels and thus each channel need to broadcast many data items. Therefore, if a set of data items broadcast in each channel have different repetition frequencies based on their access frequencies, it will give much better performance than the traditional approaches. In this paper, we propose an adaptive data allocation technique based on data access probabilities over multiple broadcast channels. Our proposed technique allows the adaptation of repetition frequency of each data item within each channel by taking its access probabilities into at count.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.523-533
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• 2019

The convergence of engineering and IT technology has brought many changes to the industry as well as academic research. In particular, computer simulation technology has evolved to a level that can accurately simulate actual physical phenomena and analyze them in real time. In this paper, we describe the CFD technology, which is mainly used in industry, and the post processor that uses the augmented reality which is emerging as the post-processing. Research on the visualization of fluid simulation results using AR technology is actively being carried out. However, due to the large size of the result data, it is limited to researches that are published in a desktop environment. Therefore, it is limitation that needs to be reviewed in actual space. In this paper, we discuss how to solve these problems. We analyze the fluid analysis results in the post-processing, and then perform optimizing data (more than 70%)to support operation in the mobile environment. In the visualization, lightweight data is used to perform real-time tracking using cloud computing, The analysis result is matched to the screen and visualized. This allows the user to review and analyze the fluid analysis results in an efficient and immersive manner in the various spaces where the simulation is performed.

• Journal of Korea Multimedia Society
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• v.9 no.8
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• pp.1030-1036
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• 2006

The rapid proliferation of wireless networks and mobile computing applications has changed the landscape of network security. Anomaly detection is a pattern recognition task whose goal is to report the occurrence of abnormal or unknown behavior in a given system being monitored. This paper presents an efficient rough set based anomaly detection method that can effectively identify a group of especially harmful internal masqueraders in cellular mobile networks. Our scheme uses the trace data of wireless application layer by a user as feature value. Based on the feature values, the use pattern of a mobile's user can be captured by rough sets, and the abnormal behavior of the mobile can be also detected effectively by applying a roughness membership function considering weighted feature values. The performance of our scheme is evaluated by a simulation. Simulation results demonstrate that the anomalies are well detected by the method that assigns different weighted values to feature attributes depending on importance.

• Journal of Intelligence and Information Systems
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• v.18 no.3
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• pp.35-51
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• 2012

Cloud computing is internet-based computing where computing resources are offered over the Internet as scalable and on-demand services. In particular, in case a number of various cloud services emerge in accordance with development of internet and mobile technology, to select and provide services with which service users satisfy is one of the important issues. Most of previous works show the limitation in the degree of user satisfaction because they are based on so called concept similarity in relation to user requirements or are lack of versatility of user preferences. This paper presents cloud service selection reasoning which can be applied to the general cloud service environments including a variety of computing resource services, not limited to web services. In relation to the service environments, there are two kinds of services: atomic service and composite service. An atomic service consists of service attributes which represent the characteristics of service such as functionality, performance, or specification. A composite service can be created by composition of atomic services and other composite services. Therefore, a composite service inherits attributes of component services. On the other hand, the main participants in providing with cloud services are service users, service suppliers, and service operators. Service suppliers can register services autonomously or in accordance with the strategic collaboration with service operators. Service users submit request queries including service name and requirements to the service management system. The service management system consists of a query processor for processing user queries, a registration manager for service registration, and a selection engine for service selection reasoning. In order to enhance the degree of user satisfaction, our reasoning stands on basis of the degree of conformance to user requirements of service attributes in terms of functionality, performance, and specification of service attributes, instead of concept similarity as in ontology-based reasoning. For this we introduce so called a service attribute graph (SAG) which is generated by considering the inclusion relationship among instances of a service attribute from several perspectives like functionality, performance, and specification. Hence, SAG is a directed graph which shows the inclusion relationships among attribute instances. Since the degree of conformance is very close to the inclusion relationship, we can say the acceptability of services depends on the closeness of inclusion relationship among corresponding attribute instances. That is, the high closeness implies the high acceptability because the degree of closeness reflects the degree of conformance among attributes instances. The degree of closeness is proportional to the path length between two vertex in SAG. The shorter path length means more close inclusion relationship than longer path length, which implies the higher degree of conformance. In addition to acceptability, in this paper, other user preferences such as priority for attributes and mandatary options are reflected for the variety of user requirements. Furthermore, to consider various types of attribute like character, number, and boolean also helps to support the variety of user requirements. Finally, according to service value to price cloud services are rated and recommended to users. One of the significances of this paper is the first try to present a graph-based selection reasoning unlike other works, while considering various user preferences in relation with service attributes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.1
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• pp.123-134
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• 2010

In this paper we propose ubiquitous virtual reality framework and its application for fostering a sustainable content ecosystem in the convergence space of virtual reality and real space. The ubiquitous virtual reality framework supports fundamental infrastructure which consists of platforms for end-users and service providers and dual space management. The platform for the service provider allows experts to generate contents related to real objects while the platform for the end-users allows to consume, share and regenerate the contents contextually augmented over real objects. The dual space management stores, visualizes and provides the contents generated and extended by them for connecting different users and service providers. The proposed framework allows users to continuously generate, share and extend the contents and thus contribute to making multimedia service environment. We also implemented and evaluated the framework consisting of a desktop authoring platform, mobile authoring platform and a dual space management server. We then introduced a promising application scenario to show how the content ecosystem is empowered by ubiquitous virtual reality framework and is realized in our life. Consequently, we are expecting that the ubiquitous virtual reality technology will play a vital role in building continuously evolving multimedia service environment for the future computing environment.