• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.707-710
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• 2004

This paper reported the results of mock-up test on mass concrete for transfer girder using setting time difference of super retarding agent(SRA). According to test results, two mock-up structures were made. Plain concrete without placing layer reached maximum temperature after 24hours since placement and caused surface hydration cracks at top section. However, concrete with placing layer reached maximum temperature after 72hours and surface temperature was higher than center temperature, which did not cause surface crack. After form removing, no crack was observed at side surface of plain concrete, while concrete using SRA at mid section had surface scaling and settling crack. According to coring results, concrete with placing layer had a penetration crack from top section to bottom section. Therefore, the setting time difference method to reduce hydration heat will have difficulty in applying the mass concrete for transfer girder.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.54-54
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• 2010

In this study, the correlation between temperature and the gel-content of the module were analyzed through experiments. Amorphous thin-film solar cell used in this experiment has a visible light transmission performance of 10%. In addition, ethylene vinyl acetate(EVA) film and the clear glass have been used for the modulation. The most important process is to laminate the module in the manufacturing process of BIPV(Building integrated photovoltaic) module. Setting parameters of laminator in the lamination process are temperature, pressure and time. Setting conditions significantly affect the durability, watertightness and airtightness of module. The most important factor in the setting parameters is temperature to satisfy the gel-contents. The bottom and top surface temperature of module are measured according to setting temperature of laminator. The results showed $145^{\circ}C$ of max temperature of the bottom surface and $128^{\circ}C$ of max temperature of top surface on the module at the temperature condition of $160^{\circ}C$. And at the another temperature condition of laminator with $150^{\circ}C$, the max temperature do bottom and top are $117^{\circ}C$ and $134^{\circ}C$ respectively. The temperature difference between bottom and top of the module occurred, that is because heat has been blocked by the clear glass and the bottom of the cells absorb the heat from the laminator. In this particular, the temperature difference between setting temperature of the laminator and the surface temperature of the module showed $15^{\circ}C$, because the heat of laminator plate is transferred to the surface of the module and heat is lost at this time. As a results, gel-content showed 94.8%, 88.7% and 81.7% respectively according to the setting temperature $155^{\circ}C$, $150^{\circ}C$ and $145^{\circ}C$ of the laminator. In conclusion, the surface temperature of module increases, the gel-contents is relatively increased. But if the laminator plate temperature is too high, the gel-content shows rather decline in performance. Furthermore, the temperature difference between setting temperature and the surface temperature of the module is affected by laminating machine itself and the temperature of module should be considered when setting the laminator.

• 농업과학연구
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• 제49권2호
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• pp.341-355
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• 2022

This research was to examine the differences in post-harvest quality of melons depending on the harvest time after fruit setting. Musk melon cultivar 'K3' plants were grown in glass house conditions with a hydroponic system, and the fruits were harvested at 50, 60, and 70 days after fruit setting. The post-harvest characteristics of melons stored at 7℃ were measured over 32 days. The harvested fruits at 50, 60, 70 days after fruit setting did not differ significantly in weight, height, or size. Solid sugar content was highest in the fruits harvested at 70 days after fruit setting, but firmness, L* value, and respiration rate were highest in the fruits harvested at 50 days after fruit setting. When the harvested melons were stored at 7℃, 'K3' melons responded differently according to the harvest days after fruit setting. The major changes during storage of 'K3' melons can be summarized as follows: Firmness, respiration, moisture content, and general appearance index during storage were highest in the melons harvested at 50 days after fruit setting, but soluble solid content, fresh weight loss, and sensory evaluation were high in the melons harvested at 60 and 70 days after one. During storage at 7℃, there were no significant differences in the appearance of 'K3' melons harvested at different periods after fruit setting, but difference in soluble solid content and taste were noted. It is recommended that the fruit of 'K3' melon plants be harvested about 60 days after fruiting to provide consumers with the highest quality for taste and for storage.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.143-150
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• 1997

The maturity concept was adopted to predict the strength of concrete, which was subjected to same temperature conditions and variable curing conditions. Penetration test and compressive test were conducted to measure the initial and final setting time and the compressible strength of concrete specimen, respectively. Also, the temperature and time were recorded at some intervals of time for calculating the maturity. The initial and final setting were delayed as the w/c ratio increased and curing temperature decreased. The activating energy decreased as the w/c ratio increased. The relationships at the relative strength and the maturity were proposed at different w/c ratio for the same temperature curing condition, and these were applied for the variable curing conditions. The results indicated that the difference between the strength of the proposed and the specimen was big at 1 days's age but quite similar after 3 day's age.

• 한국건축시공학회지
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• 제8권5호
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• pp.119-125
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• 2008

In this paper, the estimation of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) are studied based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24\sim35$ KJ/mol with slightly difference along with mixture proportion. This value is smaller than existing value $30\sim50$ KJ/mol. Based on strength development estimation. it exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided effective strength development prediction value with super retarding agent contents and mineral admixture combination. Strength development prediction equation provided herein is possibly valid for estimating accurate strength development of the super retarding concrete at the job site.

• Restorative Dentistry and Endodontics
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• 제25권1호
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• pp.123-132
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• 2000

To overcome problems of conventional glass ionomers, resin components have been added to glass ionomers. On a continuum between glass ionomers and composites are a variety of blends, employing different proportions of acid-base and free radical reactions to bring about cure. Popular groups defined between the ends are resin-modified glass-ionomers(RMGIs), polyacid-modified composite resins(Compomers) and ionomer modified resins. These groups show different clinical properties, and in selecting these materials for a restoration, one should sufficiently understand these different setting properties. In this study, some difference in the setting characteristics of different groups of hybrid ionomers were examined. Two RMGIs (Fuji2 LC,GC / Vitremer, 3M), three Compomers (Dyract AP, Dentsply / F2000, 3M / Elan, Kerr) were involved in this study. The identification of the setting characteristics of different groups was achieved by a two-stage study. First, thermal analysis was performed by a differential scanning calorimeter, and then the hardness of each group at different depth and time were measured by a micro-hardness tester. Thermal analysis was performed to identify the inorganic filler content and to record the heat change during setting process. The setting process was progressed for each material by chemical set mode and light-cured mode. In the hardness test, samples of materials were prepared with a 6mm-diameter metal ring, and the hardness was measured at the top, and 1mm, 2.5mm, 4mm below at just after a 40 second-cure, and after 10 minutes, 24 hours, and 7 days. Statistical analysis was performed by Mann-Whitney rank sum test to assess significant differences between set modes and types of materials, and by ANOVA and T-test to evaluate the statistical meanings of data at different times and depths of each materials. Followings are findings and conclusions derived from this study. Thermal analysis; 1. Compomers show no evidence of chemical setting while RMGIs exhibit heat output during the process of chemical setting. 2. Heat of cure of RMGIs exceed Compomers. 3. The net heat output of RMGIs through light-cured mode is higher than through chemically set mode. Hardness test; 1. Initial hardness of RMGIs immediately after light cure is relatively low, but the hardness increases as time goes by. On the contrary, Comomers do not show evident increase of the hardness following time. 2. Compomers show a marked decrease of setting degree as the depth of the material increases. In RMGIs, the setting degree at different depths does not significantly differ.

• 대한소아치과학회지
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• 제8권1호
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• pp.119-125
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• 1981

The Purpose of this study was to evaluate the effect of frozen slab mixing technique on physical property of zinc phosphate cement used in Korea. Standard consistency, setting time, film thickness, solubility of cement prepared in frozen slab and room temperature slab were tested. The obtained results were as follows. 1. Amount of powder required for standard-consistency for all cements tested could be increased. 2. Setting time for all cements tested could be decreased. 3. No significant difference in film thickness. 4. Solubility for all cements tested could be decreased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술논문발표회
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• pp.41-45
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• 2002

Placing lift is applied to place mass concrete in order to reduce thermal cracks by hydration heat. But they results in cold joint between placing lifts, which bring about the loss of strength, water tightness and undesirable appearance. Therefore, in this paper, mechanical and hydration heat of mass concrete using super retarding agent developed through previous study are investigated in order to reduce the hydration heat and place it without place lift. According to test results, placing lifts combined with normal concrete and concrete containing super retarding agent have positive effects on reducing hydration heat. Especially, the crack index by thermal stress of the concrete containing super retarding agent less than a quarter, compared to that of plain concrete without placing lifts, and less than a half, compared to that of plain concrete with placing lifts.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.336-340
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• 1999

This study was performed to evaluate the physical properties of reinforced soil-mixture powder. Soil was used to be powder that passed by the No. 200 mech and the reinforcement as calcium carbonate, quicklime and portland cement used for this study to improve soil. We resulted from fineness , setting time, and compressive strength test of reinforced soil-mixture powder. We've got the two conclusions . The first , in case that we were used reinforced soil-mixture powder included some portland cement, the higher the mixture rates of the reinforcement , the wider the difference theoretical data with experimental data. The second, the setting time of reinforced soil-mixture powder is faster than soil powder itself and the reinforcement for promoting strength was proved that calcium carbonate was proper than others if we compared it with other reinforcment.

• 한국세라믹학회지
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• 제44권9호
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• pp.489-495
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• 2007

Effects of ultrafinely ground ash on the rheological properties of cement paste were investigated. Also compressive strength development and setting time of ultrafine ash blended cement mortar were investigated in the study. A sample with silica fume was included for comparison. According to the results of ultra fine ash blended cement paste in the lower W/B ratio, the fluidity were high, and the setting time was a little retarded. And the compressive strength of ultrafine ash blended mortar was increased in the long term. In the case of hardened cement paste at 28 days, $Ca(OH)_2$ contents was decreased in order of control, ultrafine ash, silica fume blended cement due to difference of the pozzolanic reaction.