• Journal of the Korean School Mathematics Society
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• v.12 no.1
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• pp.99-114
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• 2009

Although they are interested in Linear Algebra not only in science and engineering but also in humanities and sociology recently, a study of teaching linear algebra is not relatively abundant because linear algebra was taken as basic course in colleges just for 20-30 years. However, after establishing The Linear Algebra Curriculum Study Group in January, 1990, a variety of attempts to improve teaching linear algebra have been emerging. This article looks into series of studies related with teaching matrix. For this the method for teaching the concepts of matrix in relation to historico-genetic principle looking through the process of the conceptual development of matrix-determinants, matrix-systems of linear equations and linear transformation.

• The Korean Journal of Applied Statistics
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• v.30 no.5
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• pp.691-699
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• 2017

Data analysts sometimes test the equality of two normal population means by the inspection of the overlapping of two confidence intervals. This method seems simple to use; however, it is a common statistical misconception to suppose that two normal means are not significantly different because of no overlapping. This article will present transforming the confidence interval of the mean difference to individual confidence intervals that are visualized to inspect overlapping. It will also be shown that this technique can be extended when comparing the k normal population means with equal variances.

• Journal of the Korean Society of Food Culture
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• v.30 no.5
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• pp.587-595
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• 2015

The purpose of this article was to research the difference in additional marketing satisfaction by lifestyle of Korean restaurant customers (focus on foreign students at university in Gangwon province). In this research, factor analysis, cluster analysis, and ANOVA were carried out. Lifestyle was divided into seven factors and six clusters. Additional marketing satisfaction was divided into three factors. Additional marketing satisfaction showed a significant difference by lifestyle of foreign students. First, 'employee' had a highest point at C3 'convenience internet searching pursuit' but lowest point at C4 'brand preference pursuit' (p<0.001). 'Service process' had a highest point at C1 'safety health pursuit' but lowest point at C5 'effort pursuit' (p<0.001). 'Tangible clue' had a highest point at C3 'convenience internet searching pursuit' but lowest point at C5 'effort pursuit' (p<0.001). Additional marketing can reduce customer uncertainty, ambiguities, and wavering about eating at restaurants by intangibility of service. As a result, food-service corporations need to manage additional marketing as well as increase satisfaction and loyalty of customers.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.145-152
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• 2015

The article aims to apply a friction stir spot welding for producing the lap joint between AA5052 aluminum alloy and C11000 copper alloy. The dimension of the materials was 100 mm in length, 30 mm in width and 1.0 mm in thickness. The copper plate was set overlap the aluminum plate by 30 mm. The welding parameter was the rotating speed of 2500-4000 rpm, the pin inserting rate of 2-8 mm/min and the holding time of 6 sec. The mechanical properties test and the microstructure investigation were performed to evaluate the lap joint quality. The summarized results are as follows. The friction stir spot welding could produce effectively the lap joint between AA5052 and C11000 copper. Increase of the rotating speed and holding time directly affected to decrease the tensile shear strength of the lap joint. The optimized welding parameters in this study that indicated the tensile shear strength of 864 N was the rotating speed of 3500 rpm, the pin inserting rate of 6 mm/min and the holding time of 4sec. The experimental results also showed that the hardness of the weld metal was lower than that of the base materials.

• Korean Journal of Acupuncture
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• v.30 no.1
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• pp.16-20
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• 2013

Objectives : The objective of this study is to report the efficacy of acupuncture and moxibustion for the treatment of fetal breech presentation. Methods : We searched papers in PubMed, using the keywords "breech and moxibustion" and "breech and acupuncture". Search range includes randomized clinical trials(RCTs), controlled clinical trials(CCTs), case reports, and case series. Each original article must have an abstract in English. Finally, 7 RCTs from 102 were included in this review. Results : As a result of analyzing the 7 RCTs, five trials hold that moxibustion or acupuncture at BL67 has been shown to produce a positive effect for the correction of breech presentation and the other two trials indicated no beneficial effect. However, one of the latter could not come to a conclusion owing to the unsatisfactory compliance record of the participants. Conclusions : Acupuncture and moxibustion may be effective to correct fetal breech presentation. In this regard, the related clinical researches are worth to be conducted.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.3
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• pp.224-230
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• 2008

In this article, $TiO_2$ nanoparticles were synthesized by using $O_2$-enriched coflow, hydrogen, diffusion flames. We investigated the thermal stability of the flame-synthesized $TiO_2$ nanoparticles by examining the crystalline structures of the nanoparticles. Also, the results were compared with those of commercial P-25 nanoparticles. $TiO_2$ nanoparticles, which were spherical with diameters approximately ranging from 30 to 60nm, were synthesized. From the XRD analyses, about 96wt% of the synthesized nanoparticles were anatase-phase. After the heat-treatment at $800^{\circ}C$ for 30 minutes, the synthesized $TiO_2$ nanoparticles showed no significant changes of their shapes and crystalline phases. On the other hand, most of the commercial particles sintered with each other and changed to the rutile-phase. Based on the result of XRD analysis it is believed that the flame-synthesized $TiO_2$ nanoparticles have higher thermal stability at $800^{\circ}C$ than the commercial particles.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.193-195
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• 2015

The Palomar Transient Factory is a project making use of a Schmidt 48 inch telescope located on the Palomar Mountain, which is surveying the sky with dynamical cadences. It was deployed in 2009 and the observed sky region is over 1200 square degrees. We have studied the long-term periodic variabilities of the known galactic cataclysmic variables (CVs). More than 20 of the sources had been found to have long term periodic signals, ranging from several tens of days to several hundreds of days. Some possible scenarios are proposed to explain the results, such as a magnetic field change of the companion star, precession of the accretion disk, triple systems and superoutburst cycles. Some preliminary discussion will be presented in this article.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.18-23
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• 1996

Fluctuation statistics of scattering strength are not only important because they impact the performance of active sonar systems, but also because they may provide insight into the major scattering process. In this article, analysis of the statistical characteristics of bottom backscattering, measured in shallow water, are presented. The slowly moving experimental sonar was operated at 30kHz to gather data over the bottom. Spatial and temporal correlation functions of the signal amplitudes were measured. The distribution function and probability of false alarm function of the detected envelope of widebeam and narrowbeam signals were measured. An attempt was made to compare the results with existing theoretical models. The result suggests that the statistical characteristics of bottom backscattering fluctuation of moving source is differ from that of fixed source.

• Journal of Families and Better Life
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• v.30 no.5
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• pp.59-74
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• 2012

The purpose of this study was to explore the structures of consciousness on the experiences of formation and adjustment in multicultural families. A qualitative study was designed in this article. The research participants were 10 dyads of immigrant married women and their mothers-in-law. Before the marriage, the mother-in-law's expectation about her daughter-in-law was not high, and the daughter-in-law held the same opinion of her mother-in-law. During the marriage process, the mother-in-law had difficulties in terms of physical, emotional, and material aspects. The daughter-in-law endured the wedding procedure by holding onto hope and anticipation for the future. After the marriage, the mother-in-law eventually became satisfied with her daughter-in-law, and the daughter-in-law grew to feel thankful for her new family members and expressed that she was living a happy life. Consequently, the essence of formation and adjustment in multicultural families was "obtaining precious family members through the undergoing of trial and error."

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.601-607
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• 2019

Ammonia would be formed in natural gas containing small amount of nitrogen reforming process in the process natural gas, which might damage the Pt catalyst and Prox catalyst. In the article, the effect of nitrogen contents on the formation of ammonia in the reforming process has been studied. In the experiments, Ru based and Ni based catalysts were used and the concentration of ammonia in the reformate gas at various gas hourly space velocity was measured. Experimental result shows that relatively higher ammonia concentration was measured with Ru based catalyst than with Ni based catalyst. It also shows that the concentration of ammonia increased rapidly after most of the methane converted into hydrogen. Based on the experimental results to reduce ammonia concentration it might be better to finish methane conversion at the exit position of the reforming reactor to minimize the contact time of catalyst and nitrogen with high concentration of hydrogen.