• The Journal of Korean Association of Computer Education
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• v.19 no.4
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• pp.59-66
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• 2016

It has been studied to reflect the number of co-rated items for solving data sparsity problem in collaborative filtering systems. A well-known method of Jaccard index allowed performance improvement, when combined with previous similarity measures. However, the degree of performance improvement when combined with existing similarity measures in various data environments are seldom analyzed, which is the objective of this study. Jaccard index as a sole similarity measure yielded much higher prediction quality than traditional measures and very high recommendation quality in a sparse dataset. In general, previous similarity measures combined with Jaccard index improved performance regardless of dataset characteristics. Especially, cosine similarity achieved the highest improvement in sparse datasets, while similarity of Mean Squared Difference degraded prediction quality in denser sets. Therefore, one needs to consider characteristics of data environment and similarity measures before combining Jaccard index for similarity use.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2089-2099
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• 2015

This study examined the relationships between the blood heavy metal (Pb, Hg and Cd) concentration and exposure-related factors. The subjects were 2,042 (male: 953, female: 1,089) who were recruited through a National Health and Nutrition Examination Survey. Differences in the concentrations of mercury were observed in males, whereas females showed differences in lead and cadmium. Analyses of the blood concentrations according to body mass index and waist circumference showed significantly higher concentrations of mercury. In males, high-density lipoprotein cholesterol of dyslipidemia was higher than normal in the blood lead concentration. In females, low-density lipoprotein cholesterol of dyslipidemia was higher than normal in the blood lead concentration. The blood lead and cadmium concentrations of male smokers was higher than non-smokers, and cadmium showed the same results in females. The blood lead levels were higher in male alcohol consumers than non-drinkers. The blood concentrations of mercury and cadmium showed significant differences according to household income. Blood concentrations of heavy metals were closely related to exposure-related factors, and age, smoking, drinking alcohols, obesity, hyperlipidemia, and household income were found to be relevant.

• Polymer(Korea)
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• v.38 no.4
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• pp.496-501
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• 2014

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in terms of physical and chemical characteristics such as low pour point (PP), and high viscosity index (VI). This paper first reports a novel preparation route for a synthetic lubricant via alkylation of isoparaffins using a peroxide initiator without olefin. Alkylation of three kinds of isoparaffins such as i-$C_{16}$, i-$C_{18}$, and i-$C_{23}$ as well as alkylation of i-$C_{18}$ with 2-pentene using di-tert butyl peroxide initiator were conducted under various conditions to confirm alkylation reaction from isoparaffins themselves i.e; Single-molecule alkylation. Various properties of each alkylates (VI and PP) were investigated as a synthetic lubricant. Single-molecule alkylation made from i-$C_{16}$ a,nd i-$C_{18}$ showed ultra high VI (>140) and low PP (< $-30^{\circ}C$).

• Journal of Preventive Medicine and Public Health
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• v.27 no.1 s.45
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• pp.25-43
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• 1994

To estimate the factors to the inclination of the criminal violence, the content of trace minerals and toxic metals in the scalp hair were measured during the period from May 1992 to October 1992. One hundred eleven violent and 89 nonviolent criminal inmates of Taegu Correctional Institute were selected. The inmates of violent criminals were imprisoned by murder, robber, rape, injury and violent acts. Those of nonviolent criminals were swindle, larceny, and adultery and had no history of institutional violence. The contents of two toxic metals (cadmium, lead) and five trace minerals (Cu, Fe, Zn, Mg, Na) were determined by an atomic absorption spectrophotometer (IL. 551). The contents of cadmium and lead in hair of violent criminals were significantly higher as $0.56{\pm}0.14ppm,\;11.53{\pm}3.32ppm$, respectively, than $0.42{\pm}0.20ppm,\;9.63{\pm}4.31ppm$ of nonviolent group (p<0.01). But the level of copper was significantly lower than nonviolent group (p<0.05). The factors that had a significant correlation with the inclination of violence in multiple logistic regression analysis were cadmium (odds ratio=98.09), unmarried (odds ratio=0.39), many times of criminal history(odds ratio=1.57) and residence of rural area (odds ratio=0.44). The results suggest that the sub-toxic contents of cadmium and lead in the hair may be of potential effect on behavior, and the mineral analysis may be an important adjunctive diagnostic procedure. Further studies into this problem are necessary.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.267-273
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• 2011

In this paper, we proposed the method to detect brain tumor region in MR images. Our method is composed of 3 parts, detection of tumor slice, detection of tumor region and tumor boundary detection. In the tumor slice detection step, a slice which contains tumor regions is distinguished using symmetric analysis in 3D brain volume. The tumor region detection step is the process to segment the tumor region in the slice distinguished as a tumor slice. And tumor region is finally detected, using spatial feature and symmetric analysis based on the cluster information. The process for detecting tumor slice and tumor region have advantages which are robust for noise and requires less computational time, using the knowledge of the brain tumor and cluster-based on symmetric analysis. And we use the level set method with fast marching algorithm to detect the tumor boundary. It is performed to find the tumor boundary for all other slices using the initial seeds derived from the previous or later slice until the tumor region is vanished. It requires less computational time because every procedure is not performed for all slices.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.5
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• pp.23-36
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• 2010

Signcryption is a cryptographic primitive which offers authentication and confidentiality simultaneously with a cost lower than signing and encrypting the message independently. We propose a new cryptographic notion called Identity-based online/offline signcryption. The notion of online/offline scheme can be divided into two phases, the first phase is performed offline prior to the arrival of a message to be signed or encrypted and the second phase is performed online phase after knowing the message and the public key of recipient. The Online phase does not require any heavy computations such as pairings or exponents. It is particularly suitable for power-constrained devices such as smart cards. In this paper, we propose ID-based signcryption scheme and ID-based online/offline signcryption scheme where the confidentiality and authenticity are simultaneously required to enable a secure and trustable communication environment. To our best knowledge, this is the first ID-based online/offline signcryption scheme that can be proven secure in the standard model.