• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.2
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• pp.112-120
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• 2007

This paper reviews the use of parasites as 'biological tags' for studying stock analysis of salmonid fishes. Numerous definitions of stock concepts exist, but most of them essentially define a group of fish as having similar biological characteristics and being self-reproducing as stocks. It is important to manage fish stocks for human consumption and sustainable production and especially for salmonid fishes. Because these fry are considered as each country's property, it is necessary to identify and discriminate each fish stock in the open sea. Methods of separating fish stocks are very diverse. Artificial tags, parasites, otoliths scales and genetic characters have been used for stock analysis and each method has advantages and disadvantages. Of these parasites can be good biological tags because they are applied by nature at no cost. Parasites can be infected with susceptible host fishes when they enter into certain areas. Then if they move to the outside and are caught researchers can infer that the fish had been in the endemic area for a period of time during their life. Hence the host fish can be considered as naturally 'tagged' by parasites. However, if they do not pass the parasites-endemic. area, they will harbour no parasites. Therefore, researchers can discriminate each fish stocks and trace their migration routes with these biological tags. In this paper, several examples on the use of parasites as biological tags for studying salmonids, as well as other species, are listed. The advantages and limitations of parasites as biological tags are also discussed. Chum salmon (Oncorhynchus keta), the main salmonid species migrating to Korea, is distributed all around the North Pacific. Korean chum salmon are generally thought to move to the Sea of Okhotsk, the western North Pacific and the Bering Sea. However, there is no clear information on the distribution and migration pathways of Korean chum salmon, and no markers exist for separating them from others yet. Recent Korean chum salmon stock analysis including parasites information are mentioned.

• Journal of The Korean Association For Science Education
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• v.44 no.2
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• pp.167-178
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• 2024

In this study, we investigated the perceptions of science-related careers and career education among middle school science teachers. Sixty-four science teachers experienced in teaching unit 7 in the first year of middle school participated. The results of the study revealed that not only careers in science but also careers with science were found to be quite high when teachers were asked to provide examples of science-related careers. Jobs related to research/engineering, which are careers in science, comprised the highest proportion of teachers' answers, followed by jobs related to education/law/social welfare/police/firefighting/military, and health/medical, which are careers with science. However, the proportion of jobs mentioned related to installation/maintenance/production was extremely low. The skills required for science-related careers were mainly perceived to consist of tools for working and ways of working. The number of skills classified under living in the world was perceived to be extremely low across most careers, irrespective of career type. Most teachers only taught unit 7 for two to four sessions and devoted little time to science-related career education, even in general science classes. In the free semester system, a significant number of teachers responded that they provide science-related career education for more than 8 hours. Teachers mainly utilize lecture, discussion/debate, and self-study activities. Meanwhile, in the free semester system, the resource-based learning method was utilized at a high proportion compared to other class situations. Teachers generally made much use of media materials, with the use of textbooks and teacher guides found to be lower than expected. There were also cases of using materials supported by science museums or the Ministry of Education. Teachers preferred to implementing student-centered classes and utilizing various teaching and learning methods. Based on the above research results, discussions were proposed to improve teachers' perceptions of science-related careers and career education.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.3
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• pp.211-220
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• 1976

The objective of this paper is to summarize and disicuss the results of studies for the prediction of fertilizer demands up to the year of 2000, from the agromic biew points. 1. The approximated demands of fertilizers figured out from the view point of nutrient requirement and fertilizer efficiency of major crops are 1,162,000M/T (N;554,100 M/T, $P_2O_5$; 360,100 M/T and $K_2O$, 247,000 M/T) at 1980, 1,471,400 M/T (N: 694,800 M/T, $P_2O_5$;465,400M/T and $K_2O$ ;311,200 M/T) at 1990 and 1,764,00 M/T (N;812,500 M/T, $P_2O_5$; 592,300 M/T and $K_2O$;359,200 M/T) at 2000${\cdots}{\cdots}$ (Approximation I) 2. Upon the basis of approximation on the yield levels of major crops per unit area and on the expansion of arable land, the demands of fertilizers at the years of 1980, 1990 and 2000 are predicted as 1,149,300 M/T (N;603,700 M/T $P_2O_5$; 305,500 M/T and $K_2O$, 240,100 M/T) 1,551,100 M/T(N:814,700M/T, $P_2O_5$;412,300 M/T and $K_2O$;324,00 M/T) and 2,253,800 M/T (N;1,183,800M/T, $P_2O_5$; 586,400M/T and $K_2O$, 470,900 M/T), respectively${\cdots}{\cdots}$(Approximation II) 3. When the recent relationships between the increases in yeid of major crops and the amounts of fertilizers for those crops per unit area are brought into consideration for the estimation of future demands of fertilizers, the predicted demands at the years of 1980, 1990 and 2000 are 1,287.600 M/T (N;677,100 M/T, $P_2O_5$; 342,000 M/T, and $K_2O$;268,500 M/T), 2,085,600M/T (N;1,096,700 M/T, $P_2O_5$;533,900 M/T, and $K_2O$;435,000 M/T and 3,380,600 M/T (N;1,777,800M/T, $P_2O_5$;897,800M/T and $K_2O$;705,000M/T) respectively (Approximation III) 4. Approximation I will be closer estimate under such condition that only rice will maintain self suficiency and other food crops will be covered by domestic production by around 50 percent, which is not desirable situation. 5. When higher self suficiency leveles of major food crops are sought through the introduction of improved varieties and expansion of cropping area and arable land by increased land utilization and reclamation of hillside land and tidal land, the Approximations II and III will become close to reality, If improved fertilizers and improved method of fertilizer applications are widely applied at the farmers fields to increase the fertilizer efficiency the former will be closer figure, if not, the latter may be better estimates.

• Korean Journal of Agricultural Science
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• v.3 no.1
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• pp.39-51
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• 1976

As an accempt to increase thc efficiency of land use and the food production to achieve the national goal in the food self-sufficiency, nine cropping systems on the upper-land were examined in pure-stand and in mixtures of soybean, corn, potato and radish. The important conclusions of this study were summarized as follows; 1. The flowering date of soybean was two or three days earlier in pure-stand than in the mixture with corn. The maturing date two days earlier in the pure-stand than in the mixture with corn. The flowering and maturing dates were not different among various cropping systems in corn. 2. The stem length of soybean was significantly different among various cropping systems. Soybean in pure-stand was shorter in stem length than with corn. 3. The number of pods per soybean plant did not give any significant differences among various cultivation methods. 4. The length of internode and the number of nodes per soybean plant in the mixture with corn were greater than in the pure-stand. In the number of branches per plant this was reversed. 5. The average stem dry weight of soybean per 10a was not significantly different among various cultivation methods. 6. The soybean yield per 10a in the pure-stand was obviously greater than the mixture and there were significant differences among cultivation method within the mixture with corn in soybean yield. 7. The 1,000-grain weight of soybean was significantly different and those in the pure-stand was heavier than those in the mixture with corn. 8. Grain weight per soybean plant and the stem diameter in the pure-stand were significantly lesser than those in the mixture with corn. 9. In the comparisons of corn in the pure-stand and in the mixture with soybean, plant height, number of ear per 10a, mean ear weight and remember of grain per plant, 100-grain weight, ear length, ear girth and number of ear pel plant were not significantly different among various cultivation methods except for the grain yield per 10a. 10. In the economic analysis, the mixture with soybean and corn gave the greatest gross income. The combination 7 was the best which was 47.6% increase income comparing with the soybean pure-stand. 11. As it can be assumed, soybean plant was influenced greatly than corn by various cropping system. It is necessary to study more complex cropping system finding and giving more desirable multiple cropping system for the farmer.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47
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• pp.15-32
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• 2002

The endeavors enhancing the grain quality of high-yielding japonica rice were steadily continued during 1980s-1990s along with the self-sufficiency of rice production and the increasing demands of high-quality rices. During this time, considerably great progress and success was obtained in development of high-quality japonica cultivars and quality evaluation techniques including the elucidation of interrelationship between the physicochemical properties of rice grain and the physical or palatability components of cooked rice. In 1990s, some high-quality japonica rice cultivars and special rices adaptable for food processing such as large kernel, chalky endosperm, aromatic and colored rices were developed and its objective preference and utility was also examined by a palatability meter, rapid-visco analyzer and texture analyzer, Recently, new special rices such as extremely low-amylose dull or opaque non-glutinous endosperm mutants were developed. Also, a high-lysine rice variety was developed for higher nutritional utility. The water uptake rate and the maximum water absorption ratio showed significantly negative correlations with the K/Mg ratio and alkali digestion value(ADV) of milled rice. The rice materials showing the higher amount of hot water absorption exhibited the larger volume expansion of cooked rice. The harder rices with lower moisture content revealed the higher rate of water uptake at twenty minutes after soaking and the higher ratio of maximum water uptake under the room temperature condition. These water uptake characteristics were not associated with the protein and amylose contents of milled rice and the palatability of cooked rice. The water/rice ratio (in w/w basis) for optimum cooking was averaged to 1.52 in dry milled rices (12% wet basis) with varietal range from 1.45 to 1.61 and the expansion ratio of milled rice after proper boiling was average to 2.63(in v/v basis). The major physicochemical components of rice grain associated with the palatability of cooked rice were examined using japonica rice materials showing narrow varietal variation in grain size and shape, alkali digestibility, gel consistency, amylose and protein contents, but considerable difference in appearance and texture of cooked rice. The glossiness or gross palatability score of cooked rice were closely associated with the peak, hot paste and consistency viscosities of viscosities with year difference. The high-quality rice variety "IIpumbyeo" showed less portion of amylose on the outer layer of milled rice grain and less and slower change in iodine blue value of extracted paste during twenty minutes of boiling. This highly palatable rice also exhibited very fine net structure in outer layer and fine-spongy and well-swollen shape of gelatinized starch granules in inner layer and core of cooked rice kernel compared with the poor palatable rice through image of scanning electronic microscope. Gross sensory score of cooked rice could be estimated by multiple linear regression formula, deduced from relationship between rice quality components mentioned above and eating quality of cooked rice, with high probability of determination. The $\alpha$-amylose-iodine method was adopted for checking the varietal difference in retrogradation of cooked rice. The rice cultivars revealing the relatively slow retrogradation in aged cooked rice were IIpumbyeo, Chucheongyeo, Sasanishiki, Jinbubyeo and Koshihikari. A Tonsil-type rice, Taebaegbyeo, and a japonica cultivar, Seomjinbyeo, showed the relatively fast deterioration of cooked rice. Generally, the better rice cultivars in eating quality of cooked rice showed less retrogradation and much sponginess in cooled cooked rice. Also, the rice varieties exhibiting less retrogradation in cooled cooked rice revealed higher hot viscosity and lower cool viscosity of rice flour in amylogram. The sponginess of cooled cooked rice was closely associated with magnesium content and volume expansion of cooked rice. The hardness-changed ratio of cooked rice by cooling was negatively correlated with solids amount extracted during boiling and volume expansion of cooked rice. The major physicochemical properties of rice grain closely related to the palatability of cooked rice may be directly or indirectly associated with the retrogradation characteristics of cooked rice. The softer gel consistency and lower amylose content in milled rice revealed the higher ratio of popped rice and larger bulk density of popping. The stronger hardness of rice grain showed relatively higher ratio of popping and the more chalky or less translucent rice exhibited the lower ratio of intact popped brown rice. The potassium and magnesium contents of milled rice were negatively associated with gross score of noodle making mixed with wheat flour in half and the better rice for noodle making revealed relatively less amount of solid extraction during boiling. The more volume expansion of batters for making brown rice bread resulted the better loaf formation and more springiness in rice breed. The higher protein rices produced relatively the more moist white rice bread. The springiness of rice bread was also significantly correlated with high amylose content and hard gel consistency. The completely chalky and large grain rices showed better suitability far fermentation and brewing. The glutinous rice were classified into nine different varietal groups based on various physicochemical and structural characteristics of endosperm. There was some close associations among these grain properties and large varietal difference in suitability to various traditional food processing. Our breeding efforts on improvement of rice quality for high palatability and processing utility or value-adding products in the future should focus on not only continuous enhancement of marketing and eating qualities but also the diversification in morphological, physicochemical and nutritional characteristics of rice grain suitable for processing various value-added rice foods.ice foods.