• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.1
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• pp.10-19
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• 1999

In 1991, the ministry of Gov't. Administration and Home Affairs set up a minimum of one sewage disposal plant in each province. By 1995, 264 models of the capillary infiltration method were set up in 331(78%) villages and the contact oxidation method was set up in 52 places. Since the Gov't. sent a letter to each responsible officer across the country stating their disapproval of the capillary infiltration method, the environmentally friendly sewage disposal system has not been diffused. The current model(mechanical sewage disposal) being used, in agricultural and fishing villages, costs too much for maintenance and operation(\50,000 per capita per year). In particular, because of the difference in sewage characteristics of agricultural and fishing villages from urban sewage, the efficiency of the disposal system is very low. Also, because of the growing need for more disposal plants, the Gov't. is looking for cheaper alternatives. This study has analyzed 2 kinds of sewage disposal. The first is used widely in agricultural and fishing villages in Germany. The second is used widely in similar areas of Korea. It has intended to analyze the characteristics, merits and defects of the sewage disposal water plants and pebbles model which is used widely in Germany and developed compatibly for Korea.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.929-933
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• 1997

Morphological studies in the micro-end-to-end (m-E-E) and micro-side-by-side (m-S-S) aggregations were conducted by using of scanning electron microscope (SEM) for the samples precipitated by heating of the end-products of the transition of FormⅡ (left-handed helix, three peptides per turn, 31) Form Ⅰ (right-handed helix, 3.3 peptides per turn, 103) in poly(L-proline) (PLP) in acetic acid(water)-propanol (1:9 v/v) solvent. The observed morphology for the solide state shows a rope (or super helical) type and pebbles type aggregate for the (m-E-E) and (m-S-S) aggregate respectively. The viscosities were also measured during the heat-precipitation in order to elucidate the process of formation of the rope- and pebbles-type aggregates. The result for the (m-E-E) aggregations exhibit two steps, i.e., at first, the viscosity increases with time (step 1), thereafter it decrease until attain the last value (step 2). But the (m-S-S) aggregations show only one step in the decreases in viscosity. On the bases of all experimental results it is possible to propose a reasonable mechanism for the formation of the two types of aggregates of the (m-E-E) and (m-S-S).

• Earthquakes and Structures
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• v.19 no.2
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• pp.103-117
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• 2020

The effect of the foundation size on the efficiency of seismic base isolation using a layer of stone pebbles is experimentally investigated. Four scaled models of buildings with different stiffnesses (from very stiff to soft) were tested, each with the so-called small and large foundation, and exposed to four different accelerograms (different predominant periods and durations). Tests were conducted so that the strains in the model remained elastic and afterwards the models were tested until collapse. Each model was tested for the case of the foundation being supported on a rigid base and on an aseismic layer. Compared to the smaller foundation, the larger foundation results in a reduced rocking effect, higher earthquake forces and lower bearing capacity of the tested models, with respectable efficiency (reduced strain/stress, displacement and increase of the ultimate bearing capacity of the model) for the considered seismic base isolation compared to the foundation on a rigid base.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2088-2093
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• 2008

In this study, flow field measurement of the Pebble Bed Reactor(PBR) for the High Temperature Gas-cooled Reactor(HTGR) was performed. Large number of pebbles in the core of PBR provides complicated flow channel. Due to the complicated geometries, numerical analysis has been intensively made rather than experimental observation. However, the justification of computational simulation by the experimental study is crucial to develop solid analysis of design method. In the present study, a wind tunnel installed with pebbles stacked was constructed and equipped with the Particle Image Velocimetry(PIV). We designed the system scaled up to realize the room temperature condition according to the similarity. The PIV observation gave us stagnation points, low speed region so that the suspected high temperature region can be identified. With the further supplementary experimental works, the present system may produce valuable data to justify the Computational Fluid Dynamics(CFD) simulation method.

• Journal of applied mathematics & informatics
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• v.42 no.1
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• pp.77-83
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• 2024

Chung defined a pebbling move on a graph G as the removal of two pebbles from one vertex and the addition of one pebble to an adjacent vertex. The monophonic pebbling number guarantees that a pebble can be shifted in the chordless and the longest path possible if there are any hurdles in the process of the supply chain. For a connected graph G a monophonic path between any two vertices x and y contains no chords. The monophonic pebbling number, µ(G), is the least positive integer n such that for any distribution of µ(G) pebbles it is possible to move on G allowing one pebble to be carried to any specified but arbitrary vertex using monophonic a path by a sequence of pebbling operations. The aim of this study is to find out the monophonic pebbling numbers of the sun graphs, (C_n × P₂) + K₁ graph, the spherical graph, the anti-prism graphs, and an n-crossed prism graph.

• Journal of the Korean Geographical Society
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• v.3
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• pp.11-18
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• 1968

이 글에서는 다음의 내용을 다루었다. 1. 연구의 목적 2. 연구지역개관과 연구방법 3. 원형도와 거리와의 관계 4. 원형도에 의한 마멸방식고찰

• Geomechanics and Engineering
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• v.8 no.6
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• pp.859-872
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• 2015

Pebble matrix filtration (PMF) is a water treatment technology that can remove suspended solids in highly turbid surface water during heavy storms. PMF typically uses sand and natural pebbles as filter media. Hand-made clay pebbles (balls) can be used as alternatives to natural pebbles in PMF treatment plants, where natural pebbles are not readily available. Since the high turbidity is a seasonal problem that occurs during heavy rains, the use of newly developed composite clay balls instead of pure clay balls have the advantage of removing other pollutants such as natural organic matter (NOM) during other times. Only the strength properties of composite clay balls are described here as the pollutant removal is beyond the scope of this paper. These new composite clay balls must be able to withstand dead and live loads under dry and saturated conditions in a filter assembly. Absence of a standard ball preparation process and expected strength properties of composite clay balls were the main reasons behind the present study. Five different raw materials from industry wastes: Red Mud (RM), Water Treatment Alum Sludge (S), Shredded Paper (SP), Saw Dust (SD), and Sugar Mulch (SM) were added to common clay brick mix (BM) in different proportions. In an effort to minimize costs, in this study clay balls were fired to $1100^{\circ}C$ at a local brick factory together with their bricks. A comprehensive experimental program was performed to evaluate crushing strength of composite hand-made clay balls, using uniaxial compression test to establish the best material combination on the basis of strength properties for designing sustainable filter media for water treatment plants. Performance at both construction and operating stages were considered by analyzing both strength properties under fully dry conditions and strength degradation after saturation in a water bath. The BM-75% as the main component produced optimum combination in terms of workability and strength. With the material combination of BM-75% and additives-25%, the use of Red Mud and water treatment sludge as additives produced the highest and lowest strength of composite clay balls, with a failure load of 5.4 kN and 1.4 kN respectively. However, this lower value of 1.4 kN is much higher than the effective load on each clay ball of 0.04 kN in a typical filter assembly (safety factor of 35), therefore, can still be used as a suitable filter material for enhanced pollutant removal.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1941-1941
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• 2024

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.389-400
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• 1999

Habitat preferences of benthic macroinvertebrates were studied according to the different substrate composition. Although it was hard to determine the common dwellers in the habitats with cobbles and pebbles, some taxa such as Ephemera orientalis, Davidius lunatus, Tipula KUb, Isonychica japonica and Tabanus amaenus etc. occurred preferably in the habitats with gravel/sand. In all the sampling stations, the numbers of species collected in the habitats with gravel/sand were always remarkably smaller as compared with the habitats with cobbles and pebbles.

• Journal of architectural history
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• v.20 no.5
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• pp.47-61
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• 2011

This study examined the background and change of building Yeongam eupseong and characteristics and construction method of its spatial structure. The results of this study can be summarized as follows. First, Yeongam eupseong was built for the same purpose of national border defense against the invasion of Japanese army as other Eupseongs were built and it was found first in the literature in the era of King Munjong of Joseon Dynasty with the scale of three gates and 4,369 cheok of castle wall. Such a scale was continued and in particular, according to flat structure, road network and gate position shown in the map, the form and road system of Yeongam eupseong before the 19th century were mostly identical with the current ones. Second, castle wall was built over foundation by using talcum after leveling the foundation soil and castle wall can be divided into outer wall, filling part and inner wall from the section. Outer wall was constructed by inserting and layering pebbles with big irregular stone, filling part was made with talcum and riprap and inner wall with soil in several layers by keeping gradient. This building method showed common features in inserting and layering pebbles for outer wall, use of protruded base and section form compared to Jeollado Eupseong.