• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.382-389
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• 1997

To study the optimum conditions of composing with sewage sludge, the variations of temperature and $CO_2$ generation amount during composting periods were investigated. The conditions were that sewage sludge added to bulking agents such as sawdust and rice hull were used and differently treated with microorganism seeding or not, initial C/N ratio, air flow rate and initial moisture contents. The results were summarized as follows : Seeding of 5% microorganism was higher temperature than not seeding. And using rice hull as bulking agents, and adjusting 21${\sim}$22 of initial C/N ratio, $200ml/l\;{\cdot}\;min$. of air flow rate and 64${\sim}$65% of initial moisture contents were higher temperature than any other conditions. Seeding of 5% microorganism was more $CO_2$ generation amount than not seeding. And using saw dust was more $CO_2$ generation amount than using rice hull as bulking agents. In the case of initial C/N ratio, adjusting 21${\sim}$42 was also more $CO_2$ generation amount than adjusting 12${\sim}$14. Judging from the result, it should be considered that the optimum conditions of composting with sewage sludges were seeding of 5% microorganism and adjusting 21${\sim}$22 of initial C/N ratio, $200ml/l\;{\cdot}\;min$. of air flow rate and 64${\sim}$65% of initial moisture contents.

• Journal of the Korean Wood Science and Technology
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• v.31 no.4
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• pp.8-15
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• 2003

This study was carried out to investigate the dimensional stability of wood treated with PEG for better utilization of domestic small-diameter logs. Four species of ring- porous wood(Quercus mongolica F_ISCH, Quercus variabilis B_LUME, Fraxinus rhynchophylla H_ANCE, Paulownia coreana U_YEKI,) and four species of diffuse-porous wood(Prunus sargentii R_EHDER, Betula davurica P_ALL, Populus tomentiglandulosa T. L_EE, Cornus controversa H_EMSLEY) were used for this experiment. The shrinkage of wood decreased with increasing the concentration of PEG. The shrinkage of diffuse- porous woods was lower than that of ring-porous woods. The weight gain increased in proportional to the PEG concentration. Diffuse-porous woods showed a little higher weight gain than ring-porous woods. Bulking effect also increased with increasing the PEG concentration, but was in inverse proportional to the molecular weight of PEG. Diffuse-porous woods showed higher bulking effect than ring-porous woods. Consequently, diffuse-porous woods showed better dimensional stability than ring- porous woods. It was considered that dimensional stability was affected by characteristics of wood such as vessel and tylosis, and density.

• Journal of the Korea Furniture Society
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• v.11 no.2
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• pp.79-84
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• 2000

It is well-known fact that dimensional stability of wood is greatly enhanced by acetylation of wood. This dimensional stability results from bulking of the reacted acetate within the cell wall, which reduces further swelling when the modified woods come into contact with water or water vapor. The purpose of this research was to determine the water absorption and dimensional stability of the acetylated solid wood in liquid water and in humidity tests. Beech and red oak were acetylated. Moisture and water absorption of acetylated wood were quite dependent on weight percent gain(WPG). Antiswelling efficiency(ASE) was quite dependent on WPG, but was not dependent on species.

• Proceedings of the Membrane Society of Korea Conference
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• 1991.10a
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• pp.41-42
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• 1991

본 연구는 활성슬러지공법의 침전조를 막으로 대체하여 고액분리를 효과적으로 수행하도록 하는 막분리 활성슬러지 공법에 관한 것이다. 이와같은 방법은 공정자체가 간략화되는 동시에 종래법에서 슬러지 팽화(bulking)등에 의해 침전조에서 SS carry-over, 슬러지 침강성 향상을 위한 고부하처리의 곤란성, 침전조 처리수에의 SS 유출등 고액 분리의 문제점을 해소하므로, 여과, 응집침전, 혹은 활성탄흡착등의 고도처리설비없이 양질이 처리수를 얻을 수 있다고 보고 되고 있다.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.371-378
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• 1996

A prototype of expert system which can support the operation for the municipal waste water treatment plant located at Kyoung-Ki Do, Kwang-ju Kun was developed and tested. This system provides (i) tracking the cause of the problem, (ii) analysis, and (iii) solution Knowledge-base consists of about 100 production-rules for the biological wastewater process, such as bio-reactor and final clarifier. Rules were obtained from the analysis of the problems such as sludge bulking. The system provides stable process control and management and effectively helps inexperienced operators with advanced and standard technologies. Future works will focus to develop a statistical process control model and associate with expert system. The control model can process the operation data statistically; analyze the relationship between affecting factors and control variables; and provide optimum operation parameters.

• Tunnel and Underground Space
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• v.14 no.6 s.53
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• pp.411-422
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• 2004

Sinkhole subsidence occurs over abandoned mine workings and can be detrimental to human lives, damage to properties and other surface structures. In this study, simulation of sinkhole development process is performed using special finite element procedure. Especially, creation of mine voids due to roof falls and generation of goaf from broken rocks are simulated using active-passive-active finite elements. An active or solid element can be made passive or void once the tensile failure criterion is satisfied in the specified sinkhole formation zone. Upon completion of sinkhole development process, these passive elements in again be made active to simulate goal region. Several finite element models are analyzed to evaluate the relationships between sinkhole formation with width of gallery. depth of mine, roof condition and bulking factor of roof rocks. This study demonstrates that the concept of passive elements in numerical analysis can be used effectively for analyzing sinkhole formation or roof fall phenomenon in general.

• Journal of Environmental Science International
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• v.7 no.1
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• pp.96-103
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• 1998

To study the optimum conditions of composting with industrial wastewater sludge, the variations of temperature and $CO_2$ generation amount during the composting periods were investigated. The conditions were that industrial wastewater added to bulking agents such as sawdust and rice hull was used, and differently treated with microorganism seeding or not, initial C/N ratios, air flow rate and initial moisture contents, respectively. The results were summarized as follows : Seeding 5% of microorganism was higher the temperature than not seeding. And using sawdust as bulking agents, and adjusting 30~40 of Initial C/N ratio, 200ml/l.min. of k flow rate and 67~68% moisture contents were higher the temperature than any other conditions. Seeding 5% of microorganisms was higher $CO_2$ generation amount than not seeding. And that was much in the order of 7~40, 30~34 and 22~23 of initial C/N ratio. Judging from the results, it should be considered that the optimum conditions in the composting of industrial wastewater sludge were seeding of 5% microorganisms, and adjusting 30~34 of Initial C/N ratio, 200ml/l min. of air flow rate and 67~68% of Intitial moisture contents. The contents of inorganic matters and C/N ratio during the composting periods at optimum condition were a little Increased. and heavy metals contents after composting were lower than standard for fortllizer.

• Journal of Environmental Health Sciences
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• v.29 no.3
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• pp.28-34
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• 2003

This study was performed to compare the effects of chaff and sawdust as bulking materials on temperature, pH, weight and volume reduction and salinity in aerobic composting of food wastes. Volume ratios of food wastes to chaff in reactor of Control, Ch-l, Ch-2, Ch-3 and Ch-4 were 4:0, 4:1, 4:2, 4:3 and 4:4, respectively. Volume ratios of food wastes to sawdust in reactor of Control, Sd-l, Sd-2, Sd-3 and Sd-4 were 4:0, 4:1, 4:2, 4:3 and 4:4, respectively. Reactors were operated for 24 days with 1 hour stirring by 1 rpm and 2 hours aeration per day. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in the reaction at higher reaction temperature and the elongation of the high temperature reaction period. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in faster pH increase. In the volume ratio of 4:3 and 4:4, pH increased faster in food-chaff mixtures than in food-sawdust mixtures. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in faster steady state in the weight reduction rate and the volume reduction rate. The weight reduction rates of chaff mixtures were higher than those of sawdust mixtures, but the volume reduction rates of sawdust mixtures were more higher than those of chaff mixtures. Salinity increased as composting reaction proceeded, due to reduction in mass weight. The final salinity of Control was 2.79%, and the final range of salinities of chaff and sawdust mixtures were 2.18∼2.37% and 1.86∼2.05%, respectively.

• Journal of Animal Environmental Science
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• v.8 no.2
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• pp.115-118
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• 2002

This study was conducted to determine the effects of pig manure composting on emission of dinitrogen oxide ($N_2O$) that is greenhouse gas. Fresh pig manure was mixed with sawdust as bulking agent and moisture content of mixed compost was adjusted by 61.9%. After mixing bulking agent with pig manure that was left to compost with aeration in composting chamber for an initial period of 30 days. At the end of this period, that was decomposed and a second period of composting was conducted without aeration for 60 days. Temperature during the initial composting period was above $55^{\circ}C$ for 7 days. Moisture reduction rate by composting pig manure was 36.7%. $N_2O$ Produced during composting was 0.043g/T-Ng.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.193-198
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• 2012

Field and laboratory tests were performed to investigate the swelling(L value) and shrinkage modulus (C value) of soil and rock mixtures using 2 sites. According to test results, when disturbed soil and rock were mixed with same amount (5:5), the maximum density was achieved and showed 19% and 18% increased at each site comparing with the unit weight of rock only. Since measured L values of mixtures were overestimated about 4 to 11% compare to estimated values based on the conventional method. While C values were underestimated about 13~20% compare to conventional values due to the development of compacting equipments and effective construction management. When rock and soil were mixed in the ratio of 5 to 5, the unit weight of the mixture was higher than that of other mixtures and rock or soil only.