• Journal of KIISE:Computing Practices and Letters
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• v.15 no.9
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• pp.617-625
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• 2009

NAND flash memory is widely used in embedded systems because of many attractive features, such as small size, light weight, low power consumption and fast access speed. However, it requires garbage collection, which includes erase operations. Erase operation is very slow. Besides, the number of the erase operations allowed to be carried out for each block is limited. The proposed garbage collection method focuses on minimizing the total number of erase operations, the deviation value of each block and the garbage collection time. NAND flash memory consists of pages of three types, such as valid pages, invalid pages and free pages. In order to achieve above goals, we use a page rate to decide when to do garbage collection and to select the target victim block. Additionally, We implement allocating method and group management method. Simulation results show that the proposed policy performs better than Greedy or CAT with the maximum rate at 82% of reduction in the deviation value of erase operation and 75% reduction in garbage collection time.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.371-375
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• 2010

SSD is a storage medium based on NAND Flash memory. Because of its short latency, low power consumption, and resistance to shock, it's not only used in PC but also in server computers. Most SSDs use FTL to overcome the erase-before-overwrite characteristic of NAND flash. There are several types of FTL, but page mapped FTL shows better performance than others. But its usefulness is limited because of its large memory footprint for the mapping table. For example, 64MB memory space is required only for the mapping table for a 64GB MLC SSD. In this paper, we propose a novel caching scheme for the mapping table. By using the mapping-table-meta-data we construct a fully associative cache, and translate the address within O(1) time. The simulation results show more than 80 hit ratio with 32KB cache and 90% with 512KB cache. The overall memory footprint was only 1.9% of 64MB. The time overhead of cache miss was measured lower than 2% for most workload.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.9
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• pp.835-840
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• 2008

This paper proposes an enhanced recommendation technique for personalized e-commerce portal analyzing various attitudes of customer. The attitudes are classifies into three types such as "purchasing product", "adding product to shopping cart", and "viewing the product information". We implicitly track customer attitude to estimate the rating of products for recommending products. We classified user groups which have similar preference for each item using implicit user behavior. The preference similarity is estimated using the Cross Correlation Coefficient. Our recommendation technique shows a high degree of accuracy as we use age and gender to group the customers with similar preference. In the experimental section, we show that our method can provide better performance than other traditional recommender system in terms of accuracy.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.8
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• pp.842-852
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• 2010

RFID applications use tags to identify objects, but recent applications tend to include diverse sensor devices such as light, temperature, and humidity sensors as well. RFID tag information is usually processed via the event driven model. However sensor devices are usually accessed via the functional call model. Therefore application developers have to deal with mixed data access models and device dependent interface functions. In this paper, we propose a sensor reader emulator that provides a consistent access interface to sensor devices regardless of the types of devices. SRE provides a more efficient way of developing RFID applications by providing a single application programmer's view to RFID tags and sensor devices. In applications where tags are fixed to a place, SRE can replace expensive sensor tags and sensor readers with inexpensive sensor devices reducing the total cost while providing the same functionality.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.3
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• pp.235-245
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• 2005

The rapid development of computer network technology has brought the Internet as the major infrastructure to our society. But the rapid increase in malicious computer intrusions using such technology causes urgent problems of protecting our information society. The recent trends of the intrusions reflect that the intruders do not break into victim host directly and do some malicious behaviors. Rather, they tend to use some automated intrusion tools to penetrate systems. Most of the unknown types of the intrusions are caused by using such tools, with some minor modifications. These tools are mostly similar to the Previous ones, and the results of using such tools remain the same as in common patterns. In this paper, we are describing design and implementation of attacker-traceback system, which traces the intruder based on the multi-agent architecture. The system first applied SOM to classify the unknown types of the intrusion into previous similar intrusion classes. And during the intrusion analysis stage, we formalized the patterns of the tools as a knowledge base. Based on the patterns, the agent system gets activated, and the automatic tracing of the intrusion routes begins through the previous attacked host, by finding some intrusion evidences on the attacked system.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.1
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• pp.1-8
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• 2006

Since most CAD tool companies are carrying out very expensive license policies, designers are sharing CAD tools with a limited number of licenses within a design working or research group. It is important to share and use them efficiently, because CAD tool licenses are very valuable resources. Designers should know CAD tool license information such as available number of licenses, types, and configuration methods to use CAD tools properly in their group. Usually, this information is provided by managers who administrate CAD tool license servers in the specific design group. In the previous CAD tool licenses sharing methods, designers have to get CAD tool license information manually and setup the environments with their own hands, If a new designer comes into the design working group, the designer wastes unnecessary time and effort due to these manual processes. As a result, designer's productivity and utilization of CAD tools will decrease. Besides, managers also waste their time and effort, since they should provide CAD tool license information manually to each desiEner. In this paper, we present a more efficient scheme to share CAD tool licenses based on directory service. The proposed method automates not only the communication processes between managers and designers, but also the license configuration steps. We expect this scheme will reduce time and effort of designers and managers as well as enhance the utilization of CAD tools.

• Journal of Digital Contents Society
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• v.13 no.1
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• pp.119-127
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• 2012

In this study, it was witnessed that a variety of tests are implemented in a type of convergence of multimedia such as photos, sounds, and videos as well as letters and drawings, components of existing traditional comics as comics are digitalized and are converted to various devices. Therefore, we studied the concept of multimedia comics as a basis of this study by judging that new barometer to comics lies in convergence with such multimedia. After recognizing components of multimedia comics which are currently emerging, we categorized them into three types depending on how to use these elements. First, convergence type webtoon has a very similar format with existing vertical scrolling webtoon and has characteristics that background & effects sounds are added to emphasize the features of webtoon, or photos or videos are inserted in part, and there is no function to control these elements; Second, motion comic, a medium format between comic and animation has a characteristic that sound, video, paging are auto-played like watching animation but it keeps the format of comics within one frame; Third, interactive comic has a characteristic that effects sound, motion, and story are made by active participation of viewers. As a result of analyzing comics which having above multimedia characteristics, its implications are as followings: First, multimedia elements should be used depending on genre, age, and media; Second, high level of control technology considering the features of comic-viewers is needed. In other words, in continuously evolving media environments, comic contents being proper to targets and use purposes of viewers should be developed. For this, multimedia elements of comics should be used in order that comic-viewers can have active & interactive communication with contents.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.4
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• pp.467-478
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• 1999

실시간 태스크의 최악 실행시간을 예측할 때 과예측이 발생하는 원인은, 첫째 프로그램의 동적인 최악 실행 행태를 정적으로 분석하는 것이 근본적으로 어렵기 때문이며, 둘째 최근의 RISC 형태 프로세서에 포함되어 있는 파이프라인 실행 구조와 캐쉬 등이 그러한 정적 분석을 더욱 어렵게 만들기 때문이다. 그런데 기존의 연구에서는 각각의 과예측 원인을 해결하기 위한 방법에 대해서만 언급하고 있을 뿐 분석의 정확도에서 각 원인이 차지하는 비중에 대해서는 언급하고 있지 않다. 이에 본 연구에서는 최악 실행시간 예측시 과예측을 유발하는 원인들, 즉 분석 요소들의 영향을 정량적으로 조사함으로써 기존의 최악 실행시간 분석 기법들이 보완해야 할 방향을 제시하고자 한다. 본 연구에서는 실험이 특정 분석 기법에 의존하지 않도록 하기 위하여 시뮬레이션 방법에 기반한다. 이를 위해 분석 요소별 스위치가 포함된 MIPS R3000 프로세서를 위한 시뮬레이터를 구현하였는데, 각 스위치는 해당 분석 요소에 대한 분석의 정확도 수준을 결정한다. 모든 스위치 조합에 대해서 시뮬레이션을 반복 수행한 다음 분산 분석을 수행하여 어떤 분석 요소가 가장 큰 영향을 끼치는지 고찰한다.Abstract Existing analysis techniques for estimating the worst case execution time (WCET) of real-time tasks still suffer from significant overestimation due to two types of overestimation sources. First, it is unavoidably difficult to predict dynamic behavior of programs statically. Second, pipelined execution and caching found in recent RISC-style processors even more complicate such a prediction. Although these overestimation sources have been attacked in many existing analysis techniques, we cannot find in the literature any description about questions like which one is most important. Thus, in this paper, we quantitatively analyze the impacts of overestimation sources on the accuracy of the worst case timing analysis. Using the results, we can identify dominant overestimation sources that should be analyzed more accurately to get tighter WCET estimations. To make our method independent of any existing analysis techniques, we use simulation based methodology. We have implemented a MIPS R3000 simulator equipped with several switches, each of which determines the accuracy level of the timing analysis for the corresponding overestimation source. After repeating simulation for all of the switch combinations, we perform the variance analysis and study which factor has the largest impact on the accuracy of the predicted WCETs.

• Biomedical Science Letters
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• v.22 no.2
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• pp.37-45
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• 2016

High risk human papillomavirus (HR-HPV) is major risk factor for uterine cervical cancer. There are approximately 15 types of HR-HPV. Liquid based cytology samples (116 samples) with high grade cervical lesions belonging to cervical intraepithelial neoplasia (CIN) 2, CIN 3, carcinoma in situ (CIS) and squamous cell carcinoma (SCC) were used after histologic confirmation. HR-HPV genotype assay was conducted using DNA chips. The HR-HPV infection rate was 81.9% with SCC samples showing the highest HR-HPV infection rate of 31%. CIN 3, CIS and CIN 2 showed infection rates of 25%, 16.4% and 9.5%, respectively. According to age with HR HPV infection rate, the 30~39 years-old group showed the highest infection rate by 92.3%. According to distribution with HR HPV genotyping, HPV 16 showed the highest infection rate by 42.3% whereas HPV 33 and HPV 58 showed infection rates of 11.7% and 10.8%, respectively. HPV 18 which is the second most common infected HPV genotype in the world showed 3.6%. Of the three most common oncogenic HR-HPV genotypes in CIN 2, we detected HPV 16, 35, 58; CIN 3 was HPV 16, 33, 58; CIS was HPV 16, 58, 33 (35/52); and SCC was HPV 16, 33, and 18 (31/52/58). Among the HPV 18, CIN 2, CIN 3, CIS and SCC showed 0.9%, 0.9%, 0% and 1.8%, respectively. The most often used preventive vaccines for cervical cancers use HPV 16 and HPV 18 as targets. However, results derived from this study suggest that a preventive vaccine against HPV 16 and HPV 18 would not be optimal for populations in this study.