• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of Broadcast Engineering
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• v.24 no.5
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• pp.849-858
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• 2019

Recent developments in computer graphics technology and image processing technology have increased interest in point cloud technology for inputting real space and object information as three-dimensional data. In particular, point cloud technology can accurately provide spatial information, and has attracted a great deal of interest in the field of autonomous vehicles and AR (Augmented Reality)/VR (Virtual Reality). However, in order to provide users with 3D point cloud contents that require more data than conventional 2D images, various technology developments are required. In order to solve these problems, an international standardization organization, MPEG(Moving Picture Experts Group), is in the process of discussing efficient compression and transmission schemes. In this paper, we provide a region division transfer method of 3D point cloud content through extension of existing MPEG-DASH (Dynamic Adaptive Streaming over HTTP)-SRD (Spatial Relationship Description) technology, quality parameters are further defined in the signaling message so that the quality parameters can be selectively determined according to the user's request. We also design a verification platform for ROUTE (Real Time Object Delivery Over Unidirectional Transport)/DASH based heterogeneous network environment and use the results to validate the proposed technology.

• Journal of Korea Multimedia Society
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• v.12 no.4
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• pp.512-520
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• 2009

Maximum intensity projection (MIP) is a volume rendering method which extracts maximum values along the viewing direction through volume data. It visualizes high-density structures, such as angio-graphic datasets so that it is frequently used in medical imaging systems. We have proposed an efficient two-step MIP acceleration method that uses the recent CPUs. First, we exploited SIMD instructions to reduce conditional branch instructions which take up a considerable part of whole rendering process, so that we improved rendering speed. Second, we proposed a new method, which accesses volume and image data successively by modifying the shear-warp rendering. This method improves memory access patterns so that cache misses are reduced. Using the current CPUs, our method improved the rendering speed by a factor of 7 than that of the shear-warp rendering.

• Journal of Popular Narrative
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• v.27 no.2
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• pp.107-142
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• 2021

Emergence of new media platform had changed relationship between the broadcaster and the viewer, which used to form 'performer-audience' structure. This research has focused on the transition of 'streamer-viewer' role in single-media broadcasting, such as Youtube or Twitch, and identify how they progress group storytelling as a team. Walter Benjam and Leslie Marmon Silko's notion of 'story and storyteller' and Erving Goffman's 'social role theory' was used to define participants' role in new media broadcasting. channel, on Youtube, was selected and analyzed as example case. The domain of 'front stage' was broadened in recorded contents comparing to live streaming. The audience of live streaming is included to the front stage during the expansion. The role of streamer, game participant, and live stream contents viewer is also adjusted during the change, which leads to group-creation of the contents. Streamer plays a role of main-storyteller and suggest identity of the community. Game participants work as sub-storyteller, filling in the blank space in game storytelling and making it sophisticated. They also perform based on community's identity, which streamer has built in advance. Lastly, live steam viewers are intermittent sub-storyteller, which seldom add up the narrative. Though, their main role is to preserve identity of game broadcasting community by reacting according to community's identity. As a result, the game broadcasting narrative is developed by combining and adding up pieces of story made in different level and role of participants. The research redefine the role of viewer and storytelling method in new media, especially in single-person broadcasting. Considering the rapid shift in recent media and contents, a new approach to the streamer-veiwer role and group storytelling of this research can be one of the new method to analyze contents produced in new media, such as Youtube.

• The KIPS Transactions:PartC
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• v.13C no.6 s.109
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• pp.767-774
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• 2006

In order to support overlay multicast with scalability and reliability, in this paper, we introduced a new multicast tree construction method and a regional multicast. The architecture we introduce efficiently transmits streaming data to the users from multicast source in an environment in which non-multicast network and multicast network. The new multicast tree construction method enables the connection with a remote relay which is an optimum condition in case there is no relay in subnet. Besides, by defining a new service type to traffic class of IPv6 header, a selective adoption or FEC and a distinctive transmission became possible. In order to verify the effect of the solution we suggested, we embodied an environment which is similar to the actual service environment by a simulator and tested it. The result of the test shows that the proposed method is more efficient than the traditional unicast approach method and the existing overlay multicast.

• The KIPS Transactions:PartA
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• v.9A no.3
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• pp.311-316
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• 2002

LZW is a popular variant of LZ78 to compress text documents. LZW yields a high compression rate and is widely used by many commercial programs. Its core idea is to assign most probably used character group an entry in a dictionary. If a group of character which is already positioned in a dictionary appears in the streaming data, then an index of a dictionary is replaced in the position of character group. In this paper, we propose a new efficient method to find least used entries in a dictionary using counter. We also achieve higher compression rate by preassigning widely used tags in hyper-text documents. Experimental results show that the proposed method is more effective than V.42bis and Unix compression method. It gives 3∼8％ better in the standard Calgary Corpus and 23∼24％ better in HTML documents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8C
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• pp.777-785
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• 2006

H.264 is the prominent video coding standard in various applications such as real-time video streaming and digital multimedia broadcasting, since it provides enhanced compression performance, error resilience tools, and network adaptation. Since compressed video stream is vulnerable to packet loss, error resilience and error concealment(EC) tools are essential for the transmission of video over the Internet. In this paper, we first propose a simple temporal EC method that improves the EC performance for intra-frame in H.264 when the amount of motion is relatively small. Then we propose a new hybrid EC method for intra-frame in H.264, which combines the spatial EC and temporal EC adaptively. The simulations are performed in packet-lossy environments, and the proposed hybrid EC method shows about 0.5-4dB PSNR improvement compared to the conventional spatial EC method that is used for intra-frame in H.264.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2S
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• pp.721-732
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• 2000

Multimedia communication systems require not only high-performance computer hardwares and high-speed networks, but also a buffer management mechanism to process many data efficiently. Two buffer handling methods, Push and Pull, are commonly used. In the Push method, a server controls the flow of dat to a client, while in the Pull method, a client controls the flow of data from a server. Those buffering schemes can be applied to the data transfer between the packet receiving buffer, which receives media data from a network server, and media playout devices, which play the recived media data. However, the buffer management mechanism in client-sides mainly support either one of the Push or the Pull method. Consequently, they have some limitations to support various media playout devices. Futhermore, even though some of them support both methods, it is difficult to use since they can't provide a unified structure. To resolved these problems, in this paper, we propose an efficient and flexible Push/Pull buffer management mechanism at client-side. The proposed buffer management scheme supports both Push and Pull method to provide various media playout devices and to support buffering function to absorb network jitter. The proposed scheme can support the various media playback devices using a single buffer space which in consequence, saves memory space compared to the case that a client keeps tow types of buffers. Moreover, it facilitates the single buffer as a mechanism for the absorbing network jitter effectively and efficiently. The proposed scheme has been implemented in an existing multimedia communication system, so called ISSA (Integrated Streaming Service Architecture), and it shows a good performance result compared to the conventional buffering methods in multimedia communication environments.

• The KIPS Transactions:PartD
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• v.16D no.6
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• pp.859-870
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• 2009

Despite the surge in the research for keyword search method over relational database, only little attention has been devoted to studying on relational data stream.The research for keyword search over relational data stream is intense interest because streaming data is recently a major research topic of growing interest in the data management. In this regard we first analyze the researches related to keyword search methodover relational data stream, and then this paper focuses on the method of minimizing the join cost occurred while processing keyword search queries. As a result, we propose an advanced keyword search method that can yield more meaningful results for users on relational data streams. We also propose a query optimization method using layered-clustering for efficient query processing.

• Journal of KIISE
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• v.42 no.1
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• pp.122-129
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• 2015

This paper proposes a method for providing the information about multimedia streams for telepresence services to heterogeneous services such as IMS (IP Multimedia Subsystem) and RTCWeb (Real-Time Communication in WEB-browsers). First of all, we design an interworking gateway for each service and suggest a procedure for providing the information about multimedia streams, which is defined by CLUE, a working group for standardization, to the heterogeneous services. We also apply the method of the actual CLUE information exchange and implement it in our experiment environment. Finally, we show that the proposed method can exchange more information than previous methods even though the media session re-establishment time is similar to legacy systems in terms of performance analysis. With the proposed method, the heterogeneous services can collect a variety of information about the telepresence service and use it according to user preference. In this way it provides rich multimedia streaming services for many areas.