• Journal of KIISE:Computing Practices and Letters
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• v.10 no.2
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• pp.134-145
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• 2004

With rapid growth in the amount of data transferred on the Internet, traditional storage systems have reached the limits of their capacity and performance. SAN (Storage Area Network), which connects hosts to disk with the Fibre Channel switches, provides one of the powerful solutions to scale the data storage and servers. In this environment, the maintenance of data consistency among hosts is an important issue because multiple hosts share the files on disks attached to the SAN. To preserve data consistency, each host can execute the disk I/O whenever disk read and write operations are requested. However, frequent disk I/O requests cause the deterioration of the overall performance of a SAN cluster. In this paper, we introduce a SANtopia global buffer manager to improve the performance of a SAN cluster reducing the number of disk I/Os. We describe the design and algorithms of the SANtopia global buffer manager, which provides a buffer cache sharing mechanism among the hosts in the SAN cluster. Micro-benchmark results to measure the performance of block I/O operations show that the global buffer manager achieves speed-up by the factor of 1.8-12.8 compared with the existing method using disk I/O operations. Also, File system micro-benchmark results show that SANtopia file system with the global buffer manager improves performance by the factor of 1.06 in case of directories and 1.14 in case of files compared with the file system without a global buffer manager.

• Journal of Information Management
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• v.34 no.2
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• pp.67-88
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• 2003

There have been increased interests in information visualization. Information visualization has been considered as a way to summarize textual data so that the users can access large amount of data more efficiently and effectively. However, many information visualization techniques stem from scientific visualization techniques, which might be difficult for the regular users to understand. More importantly, the system models used by most of the information visualization techniques do not have real world counterpart. For example, most of the users do not represent or process the textual data in terms of fisheye view or a topological map. This means that there is no affordance on the current information visualization systems from the users point of view. In this paper, we analyzed this problem by using the user interface design principles to point out what lacks in the current information visualization systems. More specifically, we have applied Nielson's Heuristic Evaluation technique to review four representative information visualization techniques. The analysis results confirmed our original hypothesis on why the current information visualization systems are not part of the mainstream information systems. Finally, we suggested to invest more efforts in improving the currently prevalent and familiar bullet list type textual information presentation method based on the usability studies and the intelligent content analysis.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.1_2
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• pp.137-146
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• 2006

Traditional live video streaming systems support the limited field of view (FOV) of image to the remote users. A server system based on the pan/tilt camera provides a user with wide view by changing the view direction of the camera mechanically. But, when many clients try to access to the server, this system can not offer their own view to every user simultaneously, and moreover it has the delay by camera motion. In order to offer wide views to several users, we propose new streaming system using the panorama image that has wide view. Our system is a kind of implementation of software pan/tilt camera. The server acquires panorama video and sends a part of the video to clients. Then, each client can control their own view. We need the effective way to reduce the average transmission data size and server burden to the compression because generally the full size of panorama video is too big to be served by the real-time streaming. To solve this problem, we propose an strip-based video compression and adaptive transmission of the compressed multiple strip videos. Experimental results show that our system can be adapted quickly to the change of view and the number of clients. Furthermore, proposed method effectively reduce the transmission data.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.3
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• pp.195-204
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• 2011

Introduction: This study examined the regulatory mechanism underlying the meal-induced changes in the hypothalamic-pituitary-adrenal gland (HPA) axis activity. Materials and Methods: Male Sprague-Dawley rats (250-300 g) were hired for two different experiments as follows; 1) rats received either 8% sucrose or 0.2% saccharin ad libitum after 48 h of food deprivation with the gastric fistula closed (real feeding) or opened (sham feeding). 2). rats received 5 ml of intra-oral infusion with 0.2% saccharin or distilled water after 48 h of food deprivation. One hour after food access, all rats were sacrificed by a transcardiac perfusion with 4% paraformaldehyde. The brains were processed for c-Fos immunohistochemistry and the cardiac blood was collected for the plasma corticosterone assay. Results: Real feedings with sucrose or saccharin and sham feeding saccharin but not sucrose, following food deprivation decreased the plasma corticosterone level. c-Fos expression in the nucleus tractus of solitarius (NTS) of the fasted rats was increased by the consumption of sucrose but not saccharin, regardless of the feeding method. On the other hand, the consumption of sucrose or saccharin with real feeding but not the sham, induced c-Fos expression in the paraventricular nucleus (PVN) of the fasted rats. The intra-oral infusion with saccharin or water decreased the plasma corticosterone level of the fasted rats. Intra-oral water infusion increased c-Fos expression in both the PVN and NTS, but saccharin only in the NTS in the fasted rats. Conclusion: Neither restoration of the fasting-induced elevation of plasma corticosterone nor the activation of neurons in the PVN and NTS after refeeding requires the palatability of food or the post-ingestive satiety and caloric load. In addition, neuronal activation in the hypothalamic PVN may not be an implication in the restoration of the fasting-induced elevation of the plasma corticosterone by oropharyngeal stimuli of palatable food.

• Journal of Digital Contents Society
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• v.12 no.1
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• pp.23-32
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• 2011

For the past few years, unlike wireless widespread United States and Japan, expensive cost and platform of the mobile web carrier underground and self-centered made achievement of domestic mobile web market sluggish. Nowadays, more and more people pay attention to the mobile web service because of the increased quality of wireless internet, development of mobile device and variety of the flat-rate payment system. However, another big problem is that mobile web is too hard to use. Also, the poor content of mobile web service is an extremely serious problem. In this paper, we put forward a new method for easy to access mobile web service which is use WINC expansion numbers and users can use these numbers to shit their own website. Along with the benefits of purchase WINC number general users are able to make website and control their website at less time and energy.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.231-239
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• 2006

In recent years, a hierarchical security architecture has been widely studied because it can efficiently protect information by allowing an authorized user access to the level of information. However, the conventional hierarchical decryption methods require several decryption keys for the high level information. In this paper, we propose a hierarchical image encryption using random phase masks and Walsh code having orthogonal characteristics. To decrypt the hierarchical level images by only one decryption key, we combine Walsh code into the hierarchical level system. For encryption process, we first perform a Fourier transform for the multiplication results of the original image and the random phase mask, and then expand the transformed pattern to be the same size and shape of Walsh code. The expanded pattern is finally encrypted by multiplying with the Walsh code image and the binary phase mask. We generate several encryption images as the same encryption process. The reconstruction image is detected on a CCD plane by a despread process and Fourier transform for the multiplication result of encryption image and hierarchical decryption keys which are generated by Walsh code and binary random phase image. Computer simulations demonstrate that the proposed technique can decrypt hierarchical information by using only one level decryption key image and it has a good robustness to the data loss such as random cropping.

• Journal of KIISE:Databases
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• v.33 no.4
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• pp.396-408
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• 2006

Moving object databases manage a large amount of past location data which are accumulated as the time goes. To retrieve fast the past location of moving objects, we need index structures which consider features of moving objects. The KDB-tree has a good performance in processing range queries. Although we use the KDB-tree as an index structure for moving object databases, there has an over-split problem in the spatial domain since the feature of moving object databases is to increase the time domain. Because the over-split problem reduces spatial regions in the MBR of nodes inverse proportion to the number of splits, there has a problem that the cost for processing spatial-temporal range queries is increased. In this paper, we propose the dynamic split strategy of the KDB-tree to process efficiently the spatial-temporal range queries. The dynamic split strategy uses the space priority splitting method for choosing the split domain, the recent time splitting policy for splitting a point page to maximize the space utilization, and the last division policy for splitting a region page. We compare the performance of proposed dynamic split strategy with the 3DR-tree, the MV3R-tree, and the KDB-tree. In our performance study for range queries, the number of node access in the MKDB-tree is average 30% less than compared index structures.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.76-86
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• 2012

The purpose of this study is to investigate the environmental equity of the accessibility to public transportation services in the city of Daegu. The 2005 census data as well as bus stop and subway station datasets were integrated for building the GIS database. Public transportation service areas were then identified by a coverage method. Mann Whitney U test was used for statistically comparing the socioeconomic characteristics over different levels of access to the public transportation services. Both Dong-gu, Suseong-gu, Dalseo-gu, and Buk-gu located outside of the city had worse accessibility than others while Jung-gu, Seo-gu, and Nam-gu had better accessibility than others. There appeared no environmental inequity pattern in terms of the percentages of men, women, and teenagers over the city of Daegu whereas there existed some environmental inequity pattern in terms of the percentages of people above the age of 65 and people below poverty line. This environmental inequity pattern would be caused by some factors. Firstly, the lower income class has tended to reside in the declined or blighted areas far away from public transportation facilities since this class can not afford to pay expensive rents and land prices around the main roads with higher accessibility. Many old people belonging to the lower income class also reside in the declined or blighted areas. Secondly, there has been no law to locate bus stops and subway stations considering residents' socioeconomic characteristics and the spatial distribution of public transportation facilities has been not managed systematically by the city government. This research would shed insight on building the public transportation policy to locate bus stops and subway stations and to select the routes of buses and subways considering the spatial distribution of residents' socioeconomic characteristics.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.6
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• pp.1-10
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• 2005

This paper describes the implementation of HTML converter for wireless internet access in wireless application protocol environment. The implemented HTML converter consists of the contents conversion module, the conversion rule set, the WML file generation module, and the frame contents reformatting module. Plain text contents are converted to WML contents through one by one mapping, referring to the converting rule set in the contents converting module. For frame contents, the first frameset sources are parsed and the request messages are reconstructed with all the file names, reconnecting to web server as much as the number of files to receive each documents and append to the first document. Finally, after the process of reformatting in the frame contents reformatting module, frame contents are converted to WML's table contents. For image map contents, the image map related tags are parsed and the names of html documents which are linked to any sites are extracted to be replaced with WML contents data and linked to those contents. The proposed conversion method for frame contents provides a better interface for the users convenience and interactions compared to the existing converters. Conversion of image maps in our converter is one of the features not currently supported by other converters.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.67-74
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• 2008

This paper proposes two peak-windowing algorithms for peak-to-average power reduction(PAPR) of orthogonal frequency division multiple access(OFDMA) downlink systems. The Proposed algorithms mitigate the effect of excessive suppression due to successive peaks or relatively high peaks of the signal. First, multi-stage peak windowing algorithm is proposed, which exploits multiple threshold of target PAPR in order to step down the peaks gradually. Secondary, variable-length peak windowing algorithm is proposed, which adapts the window length with respect to the existence of successive peaks within a half of window length. Therefore, the proposed method reduces the distortion of signal amplitude caused by window overlapping. The proposed algorithms outperform the conventional peak windowing with the aid of window-length adaptation or sequential peak power reduction. Simulation results show the efficiency of the proposed algorithms over OFDMA downlink systems, especially WiBro systems.