• Journal for History of Mathematics
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• v.18 no.1
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• pp.49-66
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• 2005

We briefly survey the history of abacus and counting rods which had been most widespread devices for arithmetical calculations. And we explain and compare the methods and principles of calculation on the abacus and counting rods. Only multiplication and division are presented here with examples. In these course we can see that the principles of calculation on the abacus are inherited from that of calculation on the counting rods. We also discuss the educational value of the abacus.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.44-52
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• 2017

In this paper, we propose a DFD (Digital Frequency Discriminator) design that has better frequency discrimination and a smaller size. Electronic warfare equipment can analyze different types of radar signal such as those based on Frequency, Pulse Width, Time Of Arrival, Pulse Amplitude, Angle Of Arrival and Modulation On Pulse. In order for electronic warfare equipment to analyze radar signals with a narrow pulse width (less than 100ns), they need to have a special receiver structure called IFM (Instantaneous Frequency Measurement). The DFD (Digital Frequency Discriminator) is usually used for the IFM. Because the existing DFDs are composed of separate circuit devices, they are bulky, heavy, and expensive. To remedy these shortcomings, we use a three delay line ($1{\lambda}$, $4{\lambda}$, $16{\lambda}$) in the DFD, instead of the four delay line ($1{\lambda}$, $4{\lambda}$, $16{\lambda}$, $64{\lambda}$) generally used in the existing DFDs, and apply the microwave integrated circuit method. To enhance the frequency discrimination, we detect the pulse amplitude and perform temperature correction. The proposed DFD has a frequency discrimination error of less than 1.5MHz, affording it better performance than imported DFDs.

• Education of Primary School Mathematics
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• v.21 no.4
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• pp.415-430
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• 2018

The purpose of this study was to get reflections on teaching numbers and operations for special education from analyzing lessons for counting, addition and subtraction of natural number with counting board for students with autism. In order to attain these purposes, this study analyzed the lessons for counting, addition and subtraction of natural number to students with autism in 4th and 6th graders in special class at regular elementary school using counting board for one hour per week for 30 weeks. According to the analysis, counting board that reveals the structure of numbers becomes an effective mathematical materials, and using the counting strategy and computation strategy can be an effective method of teaching, and it is possible to teach mathematical communication to students with autism. From this result, this study presented suggestions for teaching counting, addition and subtraction for students with disabilities.

• Proceedings of the Korean Society for History of Mathematics Conference
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• 2004.10a
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• pp.4.2-4.2
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• 2004

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.126-128
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• 2018

왜(倭)는 15-20회의 견당사를 파견하였는데, 838년 견당사의 항해와 관련해서는 이에 동승한 엔닌(円仁)이 "입당구법순례행기"를 남김으로써 그 항해의 전말이 상세하게 남아 있다. 이 기록에서 특히 관심을 끄는 것은 엔닌이 승선한 견당사선이 중국의 양주 해릉현 연안에 표착하였을 당시 기사에 언급된 정체를 알 수 없는 '누아'에 관한 기사다. 여기에서 누(?)는 ?(괭이 누), ?(김맬 누)와 같으며, '낫'이나 '호미'를 뜻하지만, 아는 중국이나 일본에서 전혀 사용되지 않는 한자어여서 글자 그대로 무엇을 의미하는 지가 불분명하다. 따라서 누아가 무엇을 의미하는지에 대해 선저 결구, 횡강력재, 피수판 등 여러 견해가 제기된 바 있다. 이 논문은 "입당구법순례행기"에 기록된 선박부재 '누아'가 무엇인지 살펴본 것이다. 먼저 "입당구법순례행기"의 여러 편역본에 '누아'가 어떻게 번역 내지 해석되고 있는지 살펴보고, 왜의 견당사선의 선형이 어땠을 지를 검토한 뒤, 이 선형의 견당사선이었을 경우 '누아'는 선박의 어떤 부재였을지를 추정해 보고자 한다. 특히 누아를 '피수판'으로 보는 최근식의 견해와 '??(진복)'의 오기로 보아 '횡강력재'로 보는 허일의 견해를 비판적으로 재검토할 것이다. 결론적으로 누아는 녹복(??)(기댈 녹, 들보 복, 즉 지지용 들보)의 오기로 판단했다. 또한 일본학자들이 견당사선을 '중국형 정크선'으로 추정하는 것과는 달리, 중국형 선박에는 선저와 상부에 횡강력재가 각각 독립해 있는 부재가 없는 것으로 보아 견당사선은 화선형 선박이거나, 한선형 선박일 것으로 추정하였다. 결론적으로 엔닌이 언급한 누아는 화선형 선박일 경우 船梁(후나바리), 한선형 선박일 경우 가룡목과 가목으로 볼 수 있다.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.53-58
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• 2006

Along with the development of costal engineering, various type of breakwaters have been built. The main purpose of breakwaters are to provide harbour protection against waves, to stabilize beaches against erosion due to large wave action, and to provide for temporary wave protection for installation on or under water surface. This paper an application example of PIV system for analyzing the flow of Floating Breakwater with double barriers. We introduce an analysis method to predict the characteristics of flow around the neighboring fields of Floating Breakwater with double barriers in order to develop a high performance model. Flow visualization has conducted in circulating water channel by a high speed camera and etc. Flowing phenomenon according to velocity distribution and flow separation around the breakwater with double barriers were obtained by 2-D PIV system.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.567-572
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• 2005

Trade between nations has been globalized since establishing the WTO(World Trade Organization). By lowering trading barriers under the WTO's system, trade in goods has been gradually increased It requires global logistic system that transports goods in between nations. To save cost of product, cargo of product is containerized and container ships to carry container cargo is going to be bigger: In the market, there are many vendors to provide artificial intelligent modules to operate container terminal. In order to integrate automated container terminal system easily and successfully, this thesis proposes high-level XML/ JMS( eXtensive Markup Language/Java Message Service) communication model and multi-agent based system architecture to share knowledges, solve problems, and active objectives by cooperating between autonomous and intelligent agents that are developed by 3rd party companies in the market. This thesis analyzed current situation of advanced automated container terminal with case studies on implemented systems and difficulties to develop automated container terminal system, reviewed technologies of intelligent agent, communication and automation that unmaned automated container terminal is required.

• Korean Journal of Environmental Agriculture
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• v.29 no.4
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• pp.354-361
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• 2010

Soil physico-chemical properties and microbial densities are affected by organic sources and soil amendment applied to improve soil environments or quality. Generally organic fertilizer effects on forage crops yield and soil properties are partly due to changes of soil composition. We investigated the effects of swine slurry (SS), swine slurry composting-biofilteration(SCB) and chemical fertilizer(F) with gypsum(G) combinations on soil physico-chemical properties and yields of summer forage crop in the Sukmoon reclaimed tidal land in Korea. The forage crops used in this experiment were corn and sorghum$\times$sudangrass hybrid(hereafter sorghum). Our results showed that the soil physico-chemical properties in the combined (F+G, SS+G, SCB+G) treatments increased contents of organic matter and exchangeable $Ca^{2+}$, but exchangeable $Na^+$, $K^+$ and $Mg^{2+}$ reduced to 1-10% for two forage crops, compared to non-combined (F, SS, SCB) treatment. The density of soil microorganism such as bacteria, actinomycetes and fungi, increased significantly by SS+G and SCB+G treatments. This means that treatment of combined organic fertilizer with G lowered salinity levels and improved with microbial growth. The combined treatments also increased the total yields 2.3-6.2% for corn and 2.0-8.7% for sorghum, compared with non-combined treatment. This experiment suggests the combined treatments could increase the total yields of summer forage crops and change of soil physico-chemical properties in the Sukmoon reclaimed tidal land in Korea.

• Journal of Practical Agriculture & Fisheries Research
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• v.24 no.1
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• pp.23-28
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• 2022

The centipede is predatory arthropod that form head and numerous segments. It is known that there are about 3,000 species worldwide and 44 species (four species and seven families) in Korea. Among them, Scolopendra subspinipes called "Wang-ji-ne" has been known as an important medicinal resource and its value is expected to increase in the future. In this study, the Scolopendra subspinipes in Korea was classified as Chilopoda through morphological analysis of forcipule and venom gland, and a method for sex determination was established. These results are expected to be used as basic data for artificial breeding of Scolopendra subspinipes in the future, and through this, it is expected that it will greatly contribute to the expansion of the Scolopendra subspinipes market as medicinal resources.

• Journal of Korean Society of Forest Science
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• v.34 no.1
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• pp.31-46
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• 1977

The study was made to give some helpful information for policy-making on ornamental tree cultivation by doing a survey on general situations, management analysis, and future prospects of the ornamental tree growing. The study was carried out through literature studies related to the subject, questionaire surveys, and on-the-spot investigation. The questionaire surveys could be divided into two parts: pre-questionaire survey and main-questionaire survey. In the pre-questionaire survey, the researchers intended to identify the total number of ornamental tree growers, cultivation areas in size and their locations. The questionaires were sent to each town and county administration authorities, forest cooperatives, and related organizations through-out the nation. The main-questionaires were prepared for detailed study and the questionaires were sent to 200 tree growers selected by option by taking considerations of the number of tree growers and the size of cultivating areas in regions. The main findings and some information obtained in the survey were as follows: 1. The total land for ornamental tree growing was amounted to 1,873.02 hectares and the number of cultivators was totaled to 2,717. 2. The main occupations of the ornamental tree growers were found in horticulture (41.9%), agronomy (25.9%), officialdom (11.3%), animal husbandry (6.5%), business circle(4.8%), and forestry (3.2%) in sequence. 3. The ornamental trees were cultivated mostly upperland (54.8), forest land (19.4%), rice paddy (11.3%) and others. 4. The educational training of the tree growers seemed quite high. The results of the survey indicated that a large number of tree growers was occupied by college graduates (38.7%), and then high school graduates (34.7%), middle school graduates (12.9%) in order. 5. The tree farming was undertaken as a side-job (41.9%) rather than main-job (23.4%), but a few of respondents rated as subsidiary-job (18.6%). 6. The management status classified by the rate of hired labors used was likely to belong to three categories: independant enterprise management (41.9%); half independant management (31.5%); and self-management (32.4%). 7. The majority of the tree growers sold their products to the consumers through middle-man channel (48.4%), or directly to the house-holder and detailers (13.7%), but a few of the respondents answered that they disposed of their products by bidding (11.2%) or by direct selling to the contractors (4.8%). 8. The channel cf marketing seemed somewhat complicated. The results of the survey were as: (1) producers ${\rightarrow}$consumers (22.6%) (2) producers ${\rightarrow}$field middle-men${\rightarrow}$consumers (33.1%) (3) producers ${\rightarrow}$field middle-men${\rightarrow}$first stage brokers${\rightarrow}$consumers (15.3%) (4) producers ${\rightarrow}$field middle-men${\rightarrow}$second stage middle-men${\rightarrow}$brokers${\rightarrow}$consumers (5.7%) (5) producers${\rightarrow}$field middle-men${\rightarrow}$third stage middle-men${\rightarrow}$second stage middlemen${\rightarrow}$brokers${\rightarrow}$consumers (4.8%) 9. It was responded that the margin for each stage of middle-men or brokers was assumed to be 30-50%(33.1%), 20-30%(32.3%), 50-100%(9.7%), and 100-200%(2.4%) in sequence. 10. The difference between the delivery price of consumers and field selling price of the producers seemed quite large. Majority of producers responded that they received half a price compared to the consumer's prices. 11. About two thirds of the respondents opposed to the measure of "Law on Preservation and Utilization of Agricultural Land" in which says that all the ornamental trees grown on flat agricultural lands less than 8 degrees in slope must be transplanted within three years to other places more than 8 degrees in slope. 12. The tree growers said that they have paid rather high land taxes than they ought to pay (38.7%), but come responded that land tax seemed to be appropriate (15.3%), and half of the respondents answered "not known". 13. The measures for the standardization of ornamental trees by size were backed up by a large number of respondents (57.3%), but one third of the respondents showed negative answer (29.8%). 14. About half of the respondents favored the systematic marketing through organization such as forest cooperatives (54%), but quite a few respondents opposed to organizing the systematic marketing channel (36.3%). 15. The necessary measures for permission in ornamental tree cultivation was rejected by a large number of respondents (49.2%) than those of favored (43.6%).