• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.582-585
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• 2006

Recently, many methods to evaluate the water content in concrete were developed. In this study, using a commercially avaliable equipment by the unit volume weight method, the water content in concrete was estimated when the moisture content in sand was changed. In order to evaluate the accuracy and the usefulness of the method, the designed water content and the measured water content were compared. The compressive strength of concrete with the variation of moisture content in sand was measured as well. As a result, it appears that in order to predict the water content in concrete, the adjustment coefficient of aggregate should be exactly estimated. It is shown that the equipment tends to underestimate the water content in concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.73-77
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• 2008

Structural lightweight concrete will reduced total loads of supporting sections and foundations in archtectural and civil structures. So, the lightweight concrete can be used widely for various purpose in the archtectural and civil structures. This paper were examined the influence of the mixing factor on the fresh and hardened properties of lightweight concrete that are used 2types of the differences properties of lightweight aggregates. According to types of lightweight aggregates, the case of synthetic lightweight aggregate are have need higher s/a; 2~4% on mixing proportion. Lightweight concrete was somewhat exhibit lower compressive strength than ordinary concrete. However it was not showed a marked difference. According to types of lightweight aggregates, the case of synthetic the lightweight aggregate are highest performance in fresh and hardened concrete.

• Proceedings of the Mineralogical Society of Korea Conference
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• 1996.10a
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• pp.25-35
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• 1996

유황은 작물에는 양적으로 인산만큼 요구되고 자연계에서 질소와 비슷하게 순환한다. 한국 토양에서 유황의 결핍은 예측이 가능한데 이는 농민이 현재까지 함유황비료의 사용을 등한히 한데 기인된다. 그러나 최근 담배, 채소, 과수 등 경제작물을 재배하는 농가에서는 함유황 비료의 수량 증수와 품질 개선을 이해하고 선호하게 되었다. 더욱이 주요 도시의 아황산가스 배출이 점차 감소하는 것도 한 이유가 된다. 최근 논 토양 1,155점, 밭토양 498점, 시설 재배지 114점을 채취 분석 유효 유황함량을 조사하였다. '88년 1차 유황 심포지엄 성적과 비교하면 작물에 유효한 제일인산칼슘 침출유황은 논과 시설재배지토양에서 뚜렷이 감소되었으며 밭토양에서는 증가하였다. 유효 유황함량인 10mg S/kg 이하인 비율은 논 8.2, 밭 $5.2\%$이었다. 논 토양의 토성속, 배수, 퇴적양식, 지형 등이 논 토양의 유황함량과 밀접한 관계가 있었으나 밭에서는 이 관계가 뚜렷하지 못했다. 조립질이고 배수가 양호하며 잔적층에서 발달된 토양에서는 유황함량이 낮아 이를 개선할 필요가 있으며 토양중 시용유황의 행동에 대한 세밀한 연구가 요구된다.

• Journal of Sericultural and Entomological Science
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• v.18 no.1
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• pp.1-5
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• 1976

This work was carried out to investigate how the effects on the growth af branches and the yield of mulberry leaves are shown, when two of each dwarf and normal branches are thinned out in sumner or early autumn. The results obtained are summarized as follows. 1) In mulberry trees after spring pruning: in case of thin out branches in summer and harvest in autumn (42 days after treatment), (1) The average length of branches in thin out trees showed 19% increase by autumn, which turned out to be 11% higher than that of non-thin out did (8%) (2) The thin out treated mulberry trees presented 9% increase in total yields of summer and autumn, when compared with those of the non-thin out trees. 2) In mulberry trees after sumner pruning: in case of thin out branches in early autumn and harvest either in autumn (15 days after treatment) or in late autumn (28 days after treatment), (1) The average length of branches showed about 6∼7% and 8%, intercase by autumn and late autumn, respectively. Thus no effects of thin out treatment could be recognized in growing of branches. (2) The thin out treated mulberry trees presented about 6% increase in total yields of early autumn, showing no significance through, when compared with those of ron-thin out treatment. Whereas the total yields of early autumn and late autumn showed 12% increase with significance at the level of 5% by thin out treatment. (3) As above mentioned, the thin out of mulberry branches brought about a good effect on yields of mulberry leaves, though less on average length of branches. It may be considered that the thin out treatment makes improve the living condition in mulberry trees and in turn induces photosynthesis actively, which results in increase the weight of leaves.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.294-300
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• 2001

The effectiveness of bottom ash on the mechanical and physical properties of Controlled Low-Strength Material(CLSM) is investigated in this study, CLSM is defined by the ACI Committee 229 as a cementitious material that is in a flowable state at the time of placement and having a specified compressive strength of 83 kgf/$\textrm{cm}^2$ or less at the age of 28 days. This study was undertaken on the use of bottom ash as a fine aggregate in CLSM. Four different levels of bottom ash with fly ash contents, 25%, 50 %, 75%, 100%, are investigated. Laboratory test results conclude that inclusion of bottom ash increases the demand for mixing water in obtaining the required flow. However, the sand was reduced because it was adjusted to maintain a constant total volume. Miかe proportions were developed for producing CLSM at three 28-day strength levels: removal with tools (less than 7 kgf/$\textrm{cm}^2$), mechanical means (less than 20 kgf/$\textrm{cm}^2$), and power equipment (less than 83 kgf/cm\`). The physical and mechanical properties supports the concept that by-product bottom ash can be successfully used in CLSM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.94-104
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• 2013

Experiments were divided into two parts; one part is to understand the basic properties of high flowable VA/VeoVa-modified cement mortar with different polymer cement ratio (P/C) and the weight ratio of fine aggregate to cement (C:F) and the other part is to investigate the effect of surface water spread on the concrete substrate on adhesion in tension. To understand the basic performance, the specimens were prepared with proportionally mixing VA/VeoVa redispersible powder, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Here, P/C were 10, 20, 30, 50 and 75% and C:F were 1:1 and 1:3. As the change of P/C and C:F unit weight, flow test, crack resistance and adhesion in tension were measured. Three specimens with good adhesion properties were selected among specimens with different P/C and C:F. The effect of surface water evenly sprayed on concrete substrate on adhesive strength is investigated. The results show that surface water on concrete substrate increases the adhesion in tension of high flowable VA/VeoVa-modified cement mortar and additionally improves the flowability compared to the non-sprayed case.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.70-77
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• 2010

This study is to investigate experimentally the influence of mixing factors, such as a mortar mix proportion of non-cement mortar, flow, and W/B, on quality characteristics of blast furnace slag powder mortar incorporating dry type recycled fine aggregates. In the characteristics of fresh mortar, the W/B increased according to the increase in the flow due to the increase in water contents, but air contents decreased due to loss of air contrary to the increase in the W/B. In the case of hardened mortar, the compressive strength showed a decrease due to the highly determined W/B inversely according to the increase in the flow through the entire age in which the compressive strength increased proportionally according to the increase in the B/W. Also, the increasing rate of such compressive strength increased more largely due to the latent hydraulic property of the BS according to the passage of the age. The flexural strength at the age of 28 days according to the increase in the B/W represented a similar level in strength values without any increases. The flexural strength for the compressive strength was distributed as a range of 1/2 ~ 1/3 and that showed a higher range than that of conventional concretes.

• Journal of Sericultural and Entomological Science
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• v.17 no.1
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• pp.27-29
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• 1975

The experiment was carried out to establish a reasonable harvesting method of mulberry shoots with branches by thin out in spring, comparing with thin-out harvest, and the results are as follows. 1. In spring, the thin-out harvest showed no remarkable effect in the results of seven days interval cutting down, except for the treatment of thinning-out thinner branches. 2. There was no significance between the control and the thinning-out thinner branches, but a tendency to increase a little harvest. Therefore, few shoots of thin branches should be cut down for the 4th instarlarvae and the rest of branches for the 5th instarlarvae. 3. The thin-out of the thicker branches showed the worst result of others, because it can hardly expect for 7 days after cutting down the thicker branches.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.1
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• pp.59-66
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• 1997

This experiment was conducted at the forage experimental field, College of Agriculture and Life Sciences, Seoul National University, Suweon in 1992 and 1993 to investigate the effects of tillage method-conventional and rotary-till, rye (Secde cereale L.) harvest date-early (April 14) and late (April 26), and rye residue treatmentno paraquat(1, 1-dinethyl-4,4'-bipyridinium dichloride) and paraquat in minimizing the adverse effects of the rye residue on growth and yield of succeeding corn(Zea mays L.). Corn plant height during the growing season was slighly taller with conventional tillage relative to rotary-till when rye was harvested in early and treated by paraquat. Corn LA1 during the growing season was slighly increased when rye was harvested in early and where conventional tillage was used with paraquat treatment. There were no differences in the leaf number and silking dates of corn among the tillage methods, harvest dates of rye and paraquat treatments. The dry matter yield of corn was significantly increased by paraquat treatment when rye was harvest in early, but no differences were found in the dry matter percentage, ear percent to total dry matter, and stover, ear and estimated TDN yields of corn among the treatments.

• Journal of Sericultural and Entomological Science
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• v.13 no.2
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• pp.81-94
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• 1971

This research is conducted to study the effect to rebbuding, death atop, yielding and occurrence of twig blight disease with the interemediate cutting periods of mulberry branch and at the picking levels of leaf remains in autumn. The results obtained are as follows: 1. Re-budding branches are decreased with delaying of interval cutting period, and that more leaves remained lesser both re-budding branches and buds are observed. Therefore, it is better that leaves remained are placed on the upper part of branch, practically with 3-5 leaf remains. It has decreased re-budding branches, in case cutting is conducted in Sept. 20 with picking leaving 3-5 leaf on. 2. With regard that all picking increases the percentage of death atop of the branch and upper half part picking increases slightly over the other treats. Although it seems unlikely to be different in the other treats with cutting period, exception of all picking, it is elucidated better that the all picking after cutting in Sept. 15 represents unusually high, seemingly effected by the temperature contition preferable to the life of twig blight disease along with the lack of branch nutrition caused by the all picking. 3. In view of yielding, it has no difference in autumn yielding with cutting period, but more picking levels of leaf remains, more yielding. In spring yield, both no picking and all picking is the lowest, in spite of cutting period. Each treat produces high yielding except the no picking if rutting is done in Sept. 15 and Sept. 20, respectively; otherwise it is done earlier or later, each treat produces low yielding. It is suggested that yielding ability in following spring affected by the autumn picking because all picking treats represent lower yielding ability than no picking ones except of cutting in Sept. 15 and Sept. 20. With respect to total yield in spring and autumn, it is represented that other treats, among which cutting in Sept. 15 and Sept. 20 is especially high, produce higher yielding than both no picking and all picking. But no difference seemed in leaf remained treats. In these respects, it may be concluded that 3-5 leaf remains after the interval cutting in Sept. 15 to Sept. 20 increases the yielding throughout two seasons and it is suggested that 3-5 leaf remains after cutting in Sept. 5 to Sept. 10 has no difference with no picking and cutting after that day. 4. Diseases in the branch remained are twig blight, massaria-bye, and Die-back, of which twig blight attacks tremendously and slight ouurence in messaria-byo and Die-back. In ouurence of twig blight, it is appeared much in all picking and seasonal occurence high in Sept. 15 with 92.9, and in Sept. 30 with 100 as index, respectively. Also it occurs ,considerably in upper part picking but little occurrence in no picing. 5. It is considered that negative correlation among re-budding percentage. No. of re-budding leaf, and spring yielding is found, seemingly without heavy correlation at -0.42, and -0.27, respectively. However, death atop of branch and occurence of twig blight has little correlation with spring yield. On the other hand, positive correlation highly appeared with the correlation coefficient at 0.8 between occurence of twig blight and death atop of branch.