• Magazine of the Korean Society of Agricultural Engineers
• /
• v.7 no.1
• /
• pp.861-876
• /
• 1965

During my stay in the Netherlands, I have studied the following, primarily in relation to the Mokpo Yong-san project which had been studied by the NEDECO for a feasibility report. 1. Unit hydrograph at Naju There are many ways to make unit hydrograph, but I want explain here to make unit hydrograph from the- actual run of curve at Naju. A discharge curve made from one rain storm depends on rainfall intensity per houre After finriing hydrograph every two hours, we will get two-hour unit hydrograph to devide each ordinate of the two-hour hydrograph by the rainfall intensity. I have used one storm from June 24 to June 26, 1963, recording a rainfall intensity of average 9. 4 mm per hour for 12 hours. If several rain gage stations had already been established in the catchment area. above Naju prior to this storm, I could have gathered accurate data on rainfall intensity throughout the catchment area. As it was, I used I the automatic rain gage record of the Mokpo I moteorological station to determine the rainfall lntensity. In order. to develop the unit ~Ydrograph at Naju, I subtracted the basic flow from the total runoff flow. I also tried to keed the difference between the calculated discharge amount and the measured discharge less than 1O~ The discharge period. of an unit graph depends on the length of the catchment area. 2. Determination of sluice dimension Acoording to principles of design presently used in our country, a one-day storm with a frequency of 20 years must be discharged in 8 hours. These design criteria are not adequate, and several dams have washed out in the past years. The design of the spillway and sluice dimensions must be based on the maximun peak discharge flowing into the reservoir to avoid crop and structure damages. The total flow into the reservoir is the summation of flow described by the Mokpo hydrograph, the basic flow from all the catchment areas and the rainfall on the reservoir area. To calculate the amount of water discharged through the sluiceCper half hour), the average head during that interval must be known. This can be calculated from the known water level outside the sluiceCdetermined by the tide) and from an estimated water level inside the reservoir at the end of each time interval. The total amount of water discharged through the sluice can be calculated from this average head, the time interval and the cross-sectional area of' the sluice. From the inflow into the .reservoir and the outflow through the sluice gates I calculated the change in the volume of water stored in the reservoir at half-hour intervals. From the stored volume of water and the known storage capacity of the reservoir, I was able to calculate the water level in the reservoir. The Calculated water level in the reservoir must be the same as the estimated water level. Mean stand tide will be adequate to use for determining the sluice dimension because spring tide is worse case and neap tide is best condition for the I result of the calculatio 3. Tidal computation for determination of the closure curve. During the construction of a dam, whether by building up of a succession of horizontael layers or by building in from both sides, the velocity of the water flowinii through the closing gapwill increase, because of the gradual decrease in the cross sectional area of the gap. 1 calculated the . velocities in the closing gap during flood and ebb for the first mentioned method of construction until the cross-sectional area has been reduced to about 25% of the original area, the change in tidal movement within the reservoir being negligible. Up to that point, the increase of the velocity is more or less hyperbolic. During the closing of the last 25 % of the gap, less water can flow out of the reservoir. This causes a rise of the mean water level of the reservoir. The difference in hydraulic head is then no longer negligible and must be taken into account. When, during the course of construction. the submerged weir become a free weir the critical flow occurs. The critical flow is that point, during either ebb or flood, at which the velocity reaches a maximum. When the dam is raised further. the velocity decreases because of the decrease\ulcorner in the height of the water above the weir. The calculation of the currents and velocities for a stage in the closure of the final gap is done in the following manner; Using an average tide with a neglible daily quantity, I estimated the water level on the pustream side of. the dam (inner water level). I determined the current through the gap for each hour by multiplying the storage area by the increment of the rise in water level. The velocity at a given moment can be determined from the calcalated current in m3/sec, and the cross-sectional area at that moment. At the same time from the difference between inner water level and tidal level (outer water level) the velocity can be calculated with the formula $h= \frac{V^2}{2g}$ and must be equal to the velocity detertnined from the current. If there is a difference in velocity, a new estimate of the inner water level must be made and entire procedure should be repeated. When the higher water level is equal to or more than 2/3 times the difference between the lower water level and the crest of the dam, we speak of a "free weir." The flow over the weir is then dependent upon the higher water level and not on the difference between high and low water levels. When the weir is "submerged", that is, the higher water level is less than 2/3 times the difference between the lower water and the crest of the dam, the difference between the high and low levels being decisive. The free weir normally occurs first during ebb, and is due to. the fact that mean level in the estuary is higher than the mean level of . the tide in building dams with barges the maximum velocity in the closing gap may not be more than 3m/sec. As the maximum velocities are higher than this limit we must use other construction methods in closing the gap. This can be done by dump-cars from each side or by using a cable way.e or by using a cable way.

• Sijohaknonchong
• /
• v.24
• /
• pp.5-46
• /
• 2006

Korean verse has flexibly changed its form and contents according to the historical background of the times. This fact arouses reader sympathy because it has reflected ideas, historical aspects and realities of the times. However, korean verse has kept its own characteristics in some ways, allowing it to exist today. It holds its form as 3 verses of three by three or four meter and three letters of the last of three verses. It makes every different version which has specific aspects of each times in the same 'sijo' area. 'Sijo' in Korean poems, is the first form that has been changed from formal to private functionally. As a result of that common verses in the Goryeo to Joseon eras were going with the stream of the times. Verse was the plate for justice so that there was no double meaning, symbols, or technical sentences. It had to show the idea of Myungchundo Jwonginryun. The theme was commonly fitted within certain areas. such as blessings, fidelity, devotion, etc. Around the end of the Joseon era, there was activation of private verses - a form of sijo with no restrictions on the length of the first two verses. Some ideas had been changed because Sarimpa gained power, domestic conflict, and the introduction of practical science. These things had an effect on the form of Sijo. After all, it shows the ideas of collapsing feudalism, resistance of confucian ideas, equality of the sexes, and opposition to the group who rule the government. Thus Sasul Sijo seems to have the tendency of resistance to reality. It was a specialty of realism poetry It explained our life in detail and reflected real life by being an intermediary of realism. This met and represented the demand of a reader's expectations. After 1905, there was new form of sijo that is very different, in form and content, from the previous versions. It was even different in areas of what people accepted. They started to think sijo was not the form of lyrical verse that is once was. It became a 'record of reading'. The form changed to 'hung or huhung' that satirized the times and the ending of a word in the last verse. Although this form could deliver the tension in statement, it was too iu from the original form. Therefore, it didn't last long, and its position got smaller because of the free verse that had western influence and was emerging in the times. In the middle of 1920, there was a movement of Sijo revival. It was lead by Choinamsun. He wrote poems and Sijo which were effected by western ideas in his early works. Although he worked with that, he took the lead in the movement of Sijo revival. He published the collection of Sijo $\ulcorner$Baekpalbunnwoi$\lrcorner$ that has one major theme-patriotic sentiment. He thought an ancient poem was a part of racial characteristics so that he expressed the main theme which represented the times and situations of his era. Modern Sijo is difficult. Sijo has to have modern and Korean verse characteristics at the same time. If it considers a modern aspect too much, it could not be distinguished from sijo and free verse. If it overly leans toward Sijo. it would seem to be too conservative which it then could be said to have no real charm of a poem. In spite of these problems, it is written constantly, because it has its own specialty. It has been focused on some works because they reflect awareness of modern times, the democratic idea, and realism. Overall, the authors of Modern Sijo express various themes by using different forms. The more what we can guess in this work, Sijo will exist permanently because of its flexibility. Furthermore, one special characteristic-flexibility of the korean verse will make it last forever and it will be a genre in Korean poetry.