• Journal of Educational Research in Mathematics
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• v.14 no.1
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• pp.71-88
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• 2004

The purpose of this study was to examine particular variables that play a significant role in the difficulty of math test items in College Scholastic Ability Test (CSAT). The study also aimed to develop a model of measuring the item difficulty. Variables correlated to item difficulty were drawn from the review of the related literature and the analysis of the content and difficulty of the past test items of CSAT. The first instrument was designed by using the correlated variables. According to the results of correlation analysis, the second instrument was made by deleting the variables which showed relatively low correlation with item difficulty and by refining some variables. Several models were proposed by using the revised instrument. The comparison of the R square and cross validity of each model reveals that integrated regression model was the most stable and accurate among the proposed models. The study also showed that statistically significant predictors were choice format, content domain, behavior domain, and the degree of item familiarity in the order of proportion of variance accounted by the predictors. Despite the limited scope of the present research, it can be suggested that its findings provide useful insights into predicting math test item difficulty.

• School Mathematics
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• v.11 no.1
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• pp.131-145
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• 2009

This research was designed to investigate the possibility to teach function concept and graph representation of functions in explicit manner toward at elementary level. Eight class-hours instruction was given to four Grade 5(age 11) students, and dynamic geometry software GSP was partially used in the class. Results indicate that the students could conceptualize the function relation, interpret linear function graphs, recognize the meaning of their slopes, and discuss the relationships among linear graphs and real life situation. Results also indicate that GSP helped students to recognize the relation between dots and the linear graph clearly and that GSP-line graph did decisive role for children to understand the meaning of graph representation of function.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.6
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• pp.718-731
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• 2003

SAN(Storage Area Network) was developed in response to the requirements of high availability of data, scalable growth, and system performance. In order to use the SAN more efficiently, most of the SAN operating software supports storage virtualization concepts that allow users to view physical storage devices of the SAN as a large volume. A logical volume manager plays a key role in storage virtualization. It realizes the storage virtualization by mapping logical addresses to physical addresses. In this paper, we design and implement an efficient and flexible mapping method for the logical volume manager. Additionally we also design and implement a free space management method for flexible mapping. Our mapping method supports a snapshot that preserves a volume image at certain time and on-line reorganization to allow users to add or remove storage devices to and from the SAN even while the system is running. To justify our mapping method, we compare it with the mapping method of the GFS (Global File System) through various experiments.

• Journal of KIISE:Software and Applications
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• v.33 no.10
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• pp.823-835
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• 2006

Multimedia is a very popular service in the Internet. But, we cannot provide multimedia service at a uniform content, because networks and devices are various. Thus, an adaptive service is needed for multimedia transmission. Video Transcoding is the good solution that can service multimedia adaptively. This paper proposes the streaming system that is composed of encoder, transcoder, decoder The encoder enhanced time complexity and PSNR in case of transcoding using PP(Prediction Period). The decoder is almost same as the traditional media player. Transcoder reduced time complexity through combination of prediction period in encoder and skipping period to control frame rate in transcoder. In simulation results, the performances of proposed scheme outperform the system with traditional transcoder in time complexity and PSNR.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.173-180
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• 2008

Certified e-Document Authority keep it with protection legal as a system a guarantee and identifies originality of an e-Record, It presume to be authenticity e-Records and contents of an e-Record prove what was not changed. But, e-Records has high medium degree of dependence and loss danger of information has very high problems. In addition, Because correction(attachment and deletion) and a revision of information are easy, a problem for integrity and the originality of an e-Record is caused. Existing system show the following inefficient. For the originality guarantee, an existing e-Documents encryption method accomplishes a encrypted process of a whole document with a symmetric key, if the information revised midway, the whole documents content must accomplish re-scanning and re-encryption process again. To get over such inefficient, this paper maximize efficiency which occurred at the time of partial information revision request by encryption and managing using the link information based on the linkage characteristics of the each page on the registered requested e-Documents, It was able to increase security configuration by minimizing problems on an information exposure through increasing complicated of the key management.

• Journal of Convergence Society for SMB
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• v.5 no.2
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• pp.1-6
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• 2015

Small and medium-sized companies lack countermeasures to secure the safety of a information system. In this circumstance, they have difficulties regarding the damage to their images and legal losses, when the information is leaked. This paper examines the information leakage of the system and hacking methods including APT attacks. Especially, APT attack, Advanced Persistent Threats, means that a hacker sneaks into a target and has a latency period of time and skims all the information related to the target, and acts in the backstage and neutralize the security services without leaving traces. Because he attacks the target covering up his traces not to reveal them, the victim remains unnoticed, which increases the damage. This study examines attack methods and the process of them and seeks a countermeasure.

• The KIPS Transactions:PartB
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• v.14B no.5
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• pp.351-360
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• 2007

Video Completion refers to a computer vision technique which restores damaged images by filling missing pixels with suitable color in a video sequence. We propose a new video completion technique to fill in image holes which are caused by removing an unnecessary object in a video sequence, where two objects cross each other in the presence of camera motion. We remove the closer object from a camera which results in image holes. Then these holes are filled by color information of some others frames. First of all, spatio-temporal volumes of occluding and occluded objects are created according to the centroid of the objects. Secondly, a temporal search technique by voxel matching separates and removes the occluding object. Finally. these holes are filled by using spatial search technique. Seams on the boundary of completed pixels we removed by a simple blending technique. Experimental results using real video sequences show that the proposed technique produces new completed videos.

• KSBB Journal
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• v.9 no.3
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• pp.339-345
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• 1994

Deletions between UASG and the GALI TATA box reduced glucose repression and allowed constitutive expression of the gene product in the absence of galactose. The relative inducer level (ratio of galactose/glucose concentrations) affected the extent of gene expression and glucose repression. Glucose repression was reduced by a factor of 2 to 5 as the relative inducer level increased. In the medium containing galactose only, induction of ${\beta}$-galactosidase synthesis by galactose increased with plasmid copy number. On the contrary, plasmid copy number did not affect significantly ${\beta}$-galactosidase synthesis in the medium containing both glucose and galactose (2% glucose＋2% galactose), which might be due to glucose repression caused by high glucose concentration. However, when the medium contained the relatively high inducer level (0.4% glucose＋0.8% galactose), ${\beta}$-galactosidase synthesis increased with plasmid copy number, indicating that the beneficial effect of higher galactose concentration was weaker than the repressive effect of higher glucose concentration.

• Korean journal of applied entomology
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• v.32 no.4
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• pp.395-406
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• 1993

This experiment was carried out to develop an artificial diet and a mass rearing system, which is essentIal in the pheromone research for Ostrmia furnacalis. Component deletion and addit.ion methods were applied t.o define the nut.ritional Importance of some components, especially yeast, Wesson's salt mixture and vitamin complex. Secondly we have developed a proper rearmg syst.em for O. furnacalis. and also tried to find out the factors affecting rapid sclerotization (dark-canning) of pupae. AddItion of yeast raIsed the pupal weight. and pupation rate. However Wesson's salt mixture got the female pupae lighter. Vitamin complex as a substitue for yeast showed a good survivahty in an early larval stage buL pupal weight was lower than that of the individuals reared on the yeast dIet. Also corrugated cardboard was found to be very good for pupation. And the rate of dark~tannmg in pupae was higher as the period of larval development was shorter.

• The Journal of Bigdata
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• v.1 no.1
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• pp.61-66
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• 2016

With big data analysis, companies use the customized marketing strategy based on customer's information. However, because of the concerns about privacy issue and identity theft, people start erasing their personal information or changing the privacy settings on social network site. Facebook, the most used social networking site, has the feature called 'Likes' which can be used as a tool to predict user's demographic profiles, such as sex and age range. To make accurate analysis model for the study, 'Likes' data has been processed by using Gaussian RBF and nFactors for dimensionality reduction. With random Forest and 5-fold cross-validation, the result shows that sex has 75% and age has 97.85% accuracy rate. From this study, we expect to provide an useful guideline for companies and marketers who are suffering to collect customers' data.