• Journal of Astronomy and Space Sciences
• /
• v.21 no.4
• /
• pp.493-504
• /
• 2004

The history books of East Asia about astronomical phenomena have the more records of the solar eclipse frequently than any other ones. It is because traditionally, the solar eclipse moaned the fate of dynasty and the king's rule. The Sun, the biggest thing in the heaven symbolized the king, and the solar eclipse foresaw that the king had the problem in private including the body, and the country might suffer from difficulties in a great scale. So the king and all of the ministers used to gather to hold a ceremony named Gusikrye(구식례) which solar eclipse may pass safely. Consequently, kings always had concernments on collecting informations of solar eclipse. Inspite of importance of solar eclipse predictions, but at the beginning of the Choseon, the predictions of the solar eclipse didn't fit. King Sejong compiled the Chiljeongsan-naepion (칠정산내편) and the Chiljeongsan-oepyeon(칠정산외편) to calculate the celestial phenomena including the solar eclipse. By the publications of these two books, the calendar making system of Choseon was firmly established. The Chiljeongsan-oepyeon adopted Huihui calendar(회회력) of Arabia. The Solar eclipse predictions of Chiljeongsan-oepyeon were relative correct compared to modern method in early Choseon dynasty.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.135-140
• /
• 2006

In the experimental study of $N_2$ purge cold flow test of impinging(FOOF) injector for determining of instability region, the whistling sound which has a specific frequency is generated. The frequency of whistling is proportional to the gas flow velocity in part of the oxidizer orifice and due to the coupling of the vibrating gas column and the natural frequency of pipe-orifice shape, the discontinuous jumping phenomena arises. The whistling phenomena have no effect on the combustion instability. Compared the damping factor of 1T1L mode with the hot fire test, the instability region of $N_2$ purge cold flow test is very much like that. It means that flow instability by impinging or mixing of jet is the main reason of combustion instability of impinging injector(FOOF) in the hot firing test.

• Journal of The Korean Association For Science Education
• /
• v.1 no.1
• /
• pp.35-44
• /
• 1978

In this study, concept centered approach and process centered approach in developing integrated science curriculum were compared and compromised between two approaches. It seems that two approaches are in antagonistic relations. The superficial conflictions getween two approaches are not because they are antagonistic in their nature, but because their interesting points are different. The concept centered approahc is interest in fundamental scientific concepts and the process centered approach is interested in scientific enquiry. If science is the composition of enquiry processes and concepts produced by enquiry processes, scientific enquiry process and scientific concept must not be inconsistant. Although concepts are not unchangeable, new concepts and advanced concepts are based on the old concepts. Enquiry activity which is not based on concepts also cannot be significant enquiry. Although fundamental concepts in science is very important, in order to apply concepts to varios phenomena, and to understand concepts more deeply the student should understand concept through the process by which the concepts are derived. As we have discussed above, only the concept centered approach or the process centered approach itself is not complete. Comparing these two uncomplete approaches to integrated science curriculum, we can find out that two approaches are in complementary relations. Because integrated science is based on the idea that natural phenomena should not be understood in fragments, but should be understood as mutually related system' the integrated science curriculum includes both the fundamental scientific concepts and scientific enquiry processes.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.6
• /
• pp.794-801
• /
• 2012

Finite Element Method is a strong tool to analyse static and dynamic problem of a structure. FEM is a good method for static problem, but for dynamic problem there are some differences between real phenomena and analyzed phenomena. Therefore some modifications are needed to identify two results. In this paper authors propose a genetic algorithm method 1) to adjust dimensions of plate for identifying natural frequencies, 2) to fit amplitude of FEM Frequency Response Function(FRF) onto it of real FRF. Analysis by raw FEM data gave questions if the results were for the same object. By only adjusting Young's modulus much better accordances were obtained, but limitation existed still. Very good agreements were achieved by shape modification and damping coefficient identification.

• Atmosphere
• /
• v.22 no.2
• /
• pp.199-208
• /
• 2012

This study was conducted in order to analyze weather characteristics during the reign of King Sejo in the Chosun Dynasty based on The Annals of the Chosun Dynasty. For this purpose, first of all, we need to determine whether The Annals of the Chosun Dynasty is a reliable material for research on weather characteristics. Thus, we compared weather phenomena during the reign of King Sejo with those in China and Japan in the same period. From the results, it was found that The Annals of the Chosun Dynasty is a useful material at least to grasp macroscopic trends in weather phenomena. Based on this assumption, we analyzed weather characteristics during the reign of King Sejo using data from The Annals of the Chosun Dynasty. During the days of King Sejo, the climate was not changed violently and there were not many disasters caused by abnormal climate such as bad harvests. This suggests that the climate was relatively stable during the period of King Sejo. As a consequence of stable weather, famine decreased markedly. However, this was not only because of stable climate but also because of the government's active efforts to reduce disasters. As droughts and floods were not frequent, social costs for recovery from disasters also decreased considerably and the saved money could be invested in the construction of social safety nets for the prevention of disasters. One of factors supporting the enthronement of King Sejo was a series of heavily damaging bad harvests during the reign of Kings Munjong and Danjong. The prevention of bad harvests was a historical mission given to the regime of King Sejo. During his reign, King Sejo promoted various policies in order to stop bad harvests. Such efforts included the government's active construction of embankments, introduction of seeds suitable for reclaimed lands, and inspiration of the consciousness of forceful farming enduring natural disasters such as floods. As a result, abnormal weathers such as floods and droughts did not lead directly to bad harvests.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.6 no.2
• /
• pp.33-45
• /
• 2003

This paper defines the prototype of the geographic-object field that links the geographic-object and the geographic-field using an object-oriented geographic information system, and then implements the flood simulation in the saemangeum water resources management system that manipulates the water quantity of saemangeum lake and the height of gate using the watershed-object field. This paper combines the natural phenomena with the artificial phenomena that occurs on the water resources of the saemangeum, and designs the object oriented class hierarchy that is composed of the total watershed-object field, and then presents the algorithm for flood control. To visualize the class hierarchy of the whole geographic-object field and the partial geographic-object field, I use the UML(Unified Modeling Language). Attributes and methods of each class can acquire the functional reusability and compatibility using the COM of the ZEUS and the Visual Basic 6.0 of Win32 APIs. By means of implementing the flood simulation in the Saemangeum water resources management system, finally, this paper contributes on the efficient management of water resources.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.5
• /
• pp.385-393
• /
• 2013

In this paper, the mechanism identification and the avoidance measures on the phenomena of transient acoustic vibration amplified at the water-supply piping system to regulate the steam temperature of the boiler reheater in 500MW class supercritical power plant are presented. The pressure pulsation waves induced by the impeller passing of two feed-water pumps with five blades are coincident with the local acoustic modes of boiler reheater water-supply piping system. There are the phenomena amplified at the peaks of 5X, 10X, 15X and 20X in spectrums of piping vibration, sound pressure, and the feed-water's pressure pulsation waves. The shut-off device is installed in the piping system for the interception of pressure pulsation waves transmitted from two feed-water pumps and the modified design change of the piping layout is applied for the acoustic resonance avoidance. The acoustic natural frequencies are separated from the harmonics of pressure pulsation waves induced by the pump impellers passing through the design change of the span length. The acoustic vibration is gone by resonance avoidance measures. As a result, more than 20 dBA reduction is achieved from 100 dBA to 80 dBA.

• Korean Journal of Veterinary Research
• /
• v.40 no.1
• /
• pp.153-165
• /
• 2000

To identify, the effects of acua-acupuncture of Bletillae rhizoma extract on the duodenal ulcer induced by HCl-aspirin in rats, the changes of histological profiles, number of mucous-producing goblet cells (PAS-positive cells), and morphology and/or number of chole-cystokinin (CCK)-8 and serotonin-immunoreactive (IR) cells in the gastrointestinal tract were observed after acua-acupuncture of Bletillae rhizoma extract on Ganshu locus ($BL_{14}$). Samples were collected at 1, 3 and 5 days after treatment. Histologically, very severe injury, atrophy of villus, necrosis of epithelial cell and hemorrhage, to the duodenal mucosa including epithelium were observed in HCl-aspirin administrated control groups, and these injuries were increased with time intervals. But in acua-acupuncture groups and nontreated normal groups, no gross lesion of ulcer was demonstrated and histologically minor injury to the apex of villas epithelium was observed. Compared to the PAS-positive cells of the control groups, those of the acua-acupuncture groups were increased. Severe degranulation of CCK-8- and serotonin-IR cells were observed in the control groups but these phenomena seldom occur in the acua-acupuncture groups. Serotonin-IR cells were significantly decreased in control groups but increased in the acua-acupuncture groups compared to control groups. However, these degranulation of IR cells of the aqua-acupuncture groups were less severe than those of normal groups, and number of serotonin-IR cells were lower than those of normal groups but these phenomena were decreased with time intervals and in 5 days after treatment, they were observed like those of normal groups. These result indicated that acua-acupuncture of Bletillae rhizoma extract would be accelerated the healing of the duodenal ulcer but the functional mechanisms were unknown.

• School Mathematics
• /
• v.12 no.4
• /
• pp.455-471
• /
• 2010

Understanding of randomness is essential for learning and teaching of probability and statistics. Understanding of randomness prompts to understand natural and social phenomena from the point of view of mathematics, and plays a role of base in understanding of judgments based on rational interpretation on these phenomena. This study examined whether pre-service teachers recognize this, and they understand randomness included in various contexts. According to results, they did not have a understanding of randomness in the context related to measuring, while they grasped randomness in simple and joint events. This implies that they lack the understanding of variability which is essential in the context of measuring. This study, therefore, suggests that the settings of measuring should be introduced into probability and statistics education, especially that data from measuring should be analyzed focusing on the variability in the data set.

• Proceedings of the Botanical Society of Korea Conference
• /
• 1987.07a
• /
• pp.191-211
• /
• 1987

Common usage of the concept of juvenility implies that there is one physiological phase, the juvenile phase, which manifests itself in the various morphological and physiological phenomena observed in juvenile higher plants. The juvenile phase is often defined as that time from seed germination until the plant attains the ability to flower regulating such behaviour. This definition precludes plants from flowering in the juvenile phase. It is of major interest, therefore, to identify the physiological controls(Bluehreife) regulating such behavior. The length of the juvenile period in higher plants ranges from one year to over 60 years in different species. The long juvenile period of seedling is the main cause of the long duration of the breeding process. I determined the length of the juvenile period in various plants and its control of phase changes in natural system in relation to factors such as plant size and age, shoot morphology, apex size, root system and phytohormonal and nutritional status is reviewed. From the own experimental and observational evidence available it appears that both hormonal and nutritional factors can be involved in control of juvenility but that a specific juvenile or flowering hormone is not involved. Grafting, ringing, scoring, root pruning and fertilization have been used to accelerate flowering, but in most cases these cultured treatments are only successful on plants that were passed the juvenile phase. It is suggested that there are intrinsic difference between the meristematic cells of the apieces of juvenile and adult shoot, which are thus determined with respect to there development potentialities. The problems associated with the maintenance of the determined state through mitosis are discussed. The properties of transitional forms of Ribes nigrum L. intermediate between the juvenile and adult phase, are descrived and there implications discussed. Analogies are drawn between juvenile phenomena in woody perennials and in herbaceous species.