• School Mathematics
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• v.15 no.2
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• pp.315-335
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• 2013

Probability has distinctive characteristics which are different from other areas of school mathematics. The critical change can be noticed in the domain, 'probability and statistics' of 2009 revised national curriculum for elementary school mathematics. This indicates that the concept of chance is supposed to be taught in the 5~6 grade band instead of the definition of probability which is moved to the middle school level. The purpose of this study is to seek desirable methods for teaching the concept of chance which reflect the achievement criteria and the attention point for teaching and learning of the curriculum at the point of time when textbooks haven't yet been developed. To do this, based on theoretical considerations and comparative analysis of the curricula in the longitudinal - latitudinal dimensions respectively, the validity of the latest curriculum change was confirmed and several learning activities were devised. And then two lessons were planned for applying these activities to eight fifth graders and were implemented along the plan. As a result, the relevance of the learning activities was examined and students' difficulties in learning the concept of chance with educational implications were discussed.

• Applied Biological Chemistry
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• v.12
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• pp.75-81
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• 1969

In order to obtain a method of scouring of raw silk and degumming of cocoon by the appling of bacterial enzyme of sericinase, a strain of proper bacteria was isolated and some properties of the enzyme produced by the isolated bacteria were studied and the following results were obtained. 1) Optimum pH and temperature were indicating 7.5 and $50^{\circ}C$. and on these conditions, the silk fibroin will get no modification at all. 2) Sericinase activity was inhibited by calcium ion in the free incubation but same ions reacted as an activator in the reaction with substrate. So, degumming of Tussah cocoon which contains calcium oxalate in the cocoon layer will be possible by the treatment of this enzyme. 3) This bacterial sericinase never gives any affection to the fibroin layer of the silk. 4) The factors of smooth-surface condition, damage of fibroin layer, touching, luster and degumming effect of the silk resulting by the enzyme treatment were more appropriate than the results of other scouring methods, saponin, alkali and saponin-alkali using methods. We expect to get the same scouring result that compared with the papain or pancreatin were applied.

• Journal of Food Hygiene and Safety
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• v.34 no.4
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• pp.367-373
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• 2019

In order to evaluate the microbiological safety of ice cream products, the total viable bacterial counts were measured in 6 kinds of ice pops, 5 kinds of non-milk fat ice cream, and 5 kinds of milk fat ice cream, sold in local markets. In addition, E. coli, S. aureus, B. cereus, and L. monocytogenes were artificially inoculated in three types of ice cream products and stored at $-5^{\circ}C$, $-10^{\circ}C$, and $-18^{\circ}C$, respectively, and after inoculation, viable cells were measured periodically. As a result of the total viable count, about 1~2 log CFU/mL was detected in 16 kinds of ice cream products. As a result of inoculation with microorganisms at various temperatures, the number of viable cells decreased as the storage period became longer, and the higher the storage temperature, the faster the microorganisms died. Especially, the microorganisms were killed faster in the ice pop products than in the other ice cream products, and the microorganisms were killed relatively slower in the milk ice cream. L. monocytogenes and S. aureus were relatively stable in frozen conditions compared to other microorganisms. The microbial contamination of commercial ice cream was lower than the allowable standard of the Korean Food Code. Microorganisms did not proliferate when the microorganism was inoculated at freezing temperature. Therefore, it is expected that the microbiological safety of frozen foods will be ensured if the sanitary control and disinfection of raw materials are thoroughly carried out during the production of frozen confections and the temperature control during distribution and storage is well maintained.