• Journal of the Korea Society of Computer and Information
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• v.17 no.1
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• pp.203-209
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• 2012

Recently, k-nearest neighbors query methods based on wireless broadcasting environment are actively studied. The advantage of wireless broadcasting environment is the scalability that enables collective query processing for unspecified users connected to the server. However, in case existing k-NN query is applied in wireless broadcasting environment, there can be a disadvantage that backtracking may occur and consequently the query processing time is increasing. In this paper proposes a hierarchical bitmap-based spatial index in order to efficiently process the k-NN queries in wireless broadcasting environment. HBI reduces the bitmap size using such bitmap information and tree structure. As a result, reducing the broadcast cycle can reduce the client's tuning time and query processing time. In addition, since the locations of all the objects can be detected using bitmap information, it is possible to tune to necessary data selectively. For this paper, a test was conducted implementing HBI to k-NN query and the proposed technique was proved to be excellent by a performance evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5A
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• pp.459-468
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• 2006

Current routing in sensor networks focuses on finding methods for energy-efficient route setup and reliable relaying of data from the sensors to the sink so that the lifetime of the network is maximized. The existing routing protocols do not have routing tables to determine a path when packets are transferred. A sensor network by a routing table increases a cost of maintaining and updating a path, because sensor nodes have characteristics to be mobile and constrained capacity and resources. This paper proposes a new routing algorithm by broadcasting a bitmap in order to reduce the number of messages transferred when routing paths are established. Each node has a routing table with a bitmap, which contains link information. A bitmap is formed two-dimensional array, which consists of each row and column represented with a bit. The node only updates its own bitmap if it receives a bitmap from another adjacent nodes after the broadcasting. There by, each node has a bitmap with partial links information not total links information on the network. The proposed routing algorithm reduces the number of messages for routing establishment at least 10% compared with the previous algorithms.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.11-16
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• 2014

Block truncation coding (BTC) is a recent technique used for compression of monochrome image data. The original algorithm of BTC implement to use the standard mean and the standard deviation. For data hiding, it is needed to modify bit-planes of an images. These modifications yields unacceptable quality of BTC images. Thus, we propose IODBTC (Improved Ordered dithering BTC) improving BTC. In this paper, we improve this problem. Experimental results show that the reconstructed secret messages are the same as the original secret messages, and that the proposed scheme exhibits a good BTC images compared to that of previous schemes.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.269-277
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• 2007

Network clustering has been proposed to provide that sensor nodes minimize energy and maximize a network lifetime by configuring clusters, Although dynamic clustering brings extra overhead like as head changing, head advertisement, it may diminish the gain in energy consumption to report attribute tasks by using cluster heads. Therefore, this paper proposes a new routing algorithm which configures cluster to reduce the number of messages when establishing paths and reports to the sink by way of cluster heads when responding sens ing tasks. All sensor nodes only broadcast bitmap once and maintain a bitmap table expressed by bits, allowing them to reduce node energy and to prolong the network lifetime. After broadcasting, each node only updates the bitmap without propagation when the adjacent nodes broad cast same query messages, This mechanism makes nodes to have abundant paths. By modifying the query which requests sensing tasks, the size of cluster is designed dynamically, We try to divide cluster by considering the number of nodes. Then, all nodes in a certain cluster must report to the sub- sink node, The proposed routing protocol finds easily an appropriate path to report tasks and reduces the number of required messages for the routing establishment, which sensor nodes minimize energy and maximize a network lifetime.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.1
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• pp.25-30
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• 2008

In this paper, we propose a color quantization method regarding facial image for mobile services. For facial images, skin colors are more emphasized. First, we extract skin-color mask in the image and divide the image into two regions. Next, we extract color pallette for two regions respectively. In the proposed method, the loss in the face region is minimized and it can be useful for mobile services considering facial images. From the 8-bit color quantization experiment, we show that the proposed method works well.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.37-43
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• 2009

In this paper, we proposed that a novel method base on a binary image that technique is proposed for data hiding into binary images and halftone image. A binary image is bitmap image and halftone is composed by two-tone value in a limited region in an image. For this reason, it is not easy to hide messages in binary images. PWLC is a new method to hide a message in binary images. However, it yields images of unacceptable quality, unless you should change very few of it. Therefore, in order to solve this problem, we used run-length method into binary images. That is, we find a proper region to hide messages. In this paper, we proposed new method to hide messages in binary images. In addition, we proved that our algorithm is better than PWLC through the experiment.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.6
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• pp.27-34
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• 2009

Block truncation coding (BTC) is a simple and efficient image compression technique. However, it yields images of unacceptable quality and significant blocking effects are seen when the block size is increasing. Ordered dither block truncation coding (ODBTC) was proposed to solve above problem maintaining the same compression capability. In this paper, we propose a data hiding method which can be applied to halftone images. EMD was developed by Zhang and Wang [6] for data hiding in the grayscale image. Therefore, EMD is not proper for bitmap images. In this paper, we show that EMD can be used to apply bitmap halftone image. In our experiments, we prove that our method is efficient in a halftone image.

• The KIPS Transactions:PartD
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• v.16D no.2
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• pp.191-200
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• 2009

Location based services (LBSs) have drawn huge attention as the growing number mobile devices and wireless technology demand more pervasive information access. In LBSs, Constraint nearest neighbor queries are one of the important queries of human to fulfill his desired quickly through wireless technology. We propose new query processing of constrained nearest neighbor query on the air to support mobile clients which demand optimal uses of wireless broadcast channel and using minimum battery power of client. First we proposed NN query processing with constrained region and then explain the novel NN query processing with various types of constraints. We have proposed novel algorithms to support Constrained Nearest Neighbor queries on the air based on Distributed Spatial Index and Bitmap-based Spatial Index.