• Tunnel and Underground Space
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• v.18 no.1
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• pp.33-43
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• 2008

The techniques for measuring the bulking factor of rock mass in subsidence area have never been well known all over the world. The volumetric expansion ratios obtained from blasting operation were the only way of acquiring the bulking factor of rock mass. The bulking factor of rock mass obtained from blasting operation, however, has been seldom classified in a certain criterion. Also the bulking factor of rock mass can be very dependent upon rock types. In order to overcome this limitation obtained from these reasons, the authors studied the experimental bulking factor of rock mass according to the stacking shapes as well as the overburden stresses. Gneiss, limestone and shale were chosen for testing specimens, and each bulking factor has been measured with laboratory test of applying a constant load on the fragmented rock specimens.

• Tunnel and Underground Space
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• v.18 no.6
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• pp.436-446
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• 2008

The volumetric expansion ratio of rock mass on the subsidence occurrence area can explain why the depth of the surface subsidence is lower than the height of an opening; it is because the empty space of the gangway is filled with the broken rock. But, until now, when the surface subsidence mechanism is studied without consideration of the volumetric expansion ratio, it is usually overlooked that the amount of subsidence occurrence can be overestimated. Therefore, in this study, the authors researched the subsidence occurrence mechanism with a new theoretical approaching method. The volumetric expansion ratio obtained from this method has been applied to the numerical simulations. The authors adopted the UDEC(Universal Distinct Element Code) for their discontinuum numerical analysis, because this program has an advantage for analyzing the behavior of rock discontinuities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.8
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• pp.706-713
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• 2007

The jet structure issuing from a conventional convergent nozzle of variable expansion rate is compared with the result from the nozzle of a constant expansion rate using a normal type annular slit. In experiments, to investigate the jet characteristics between the two cases of jet, the mean velocity of nozzle exit is fixed to be 90m/s, the pressures along the jet axis and radial directions are measured by a scanning valve system moving with 3-axis auto-traverse unit, and the velocity distribution obtained by calculation from the measured static and total pressures is compared. Also to obtain the highly stable and convergence jets, it is turned out that the flow through a nozzle of constant expansion rate using the Coanda effect with an annular slit is the most preferable than that case through variable expansion rate nozzle. Furthermore, it is found that the pressure drop along the nozzle for the constant expansion rate nozzle is small relatively against to the case of variable expansion rate nozzle.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2016.11a
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• pp.319-321
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• 2016

본 논문에서는 지반함몰이 발생한 현장에 긴급복구를 위한 팽창기능제의 개발에 대한 내용이다. 현재 유동화토에 대한 기준이 없어 공동에 채워지는 채움재와 비슷한 압축강도인 0.3MPa을 기준으로 하여 흙의 일축압축시험 방법을 이용하여 실험을 진행하였다. 팽창기능제의 최적배합 실험과 팽창률에 따른 압축강도를 측정하여 뒤채움재로써의 기능 특성을 평가하였다. 실험결과, 팽창기능제 A의 경우 팽창률 750%이하에서 팽창기능제 B의 경우는 모든 실험체에서 목표 강도를 만족하였다.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.131-138
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• 2017

In this study, the expansion and compressive strength tests of emergency restoration material were carried out to restore cavity causing ground subsidence. The expansion and compressive strength characteristics according to component ratio of main material - hardener and mix proportion of blowing agent - accelerator were analyzed based on the test results. As a result of the relationship of curing time - expansion ratio analyses, it confirmed that expansion ratio decreased with reduced curing time regardless of mix proportion of blowing agent - accelerator in main material, if component ratio of hardener increased. This means that component ratio of the main material - hardener had greatly affected the expansion ratio. The compressive strength characteristics of emergency restoration material confirmed that strength was affected by mix proportion of blowing agent - accelerator. Therefore, it is necessary to apply reasonable component ratio and mix proportion to consider the required injection time, expansion ratio and strength of restoration material, when emergency restoration in ground cavity is required.

• Culinary science and hospitality research
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• v.21 no.6
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• pp.218-228
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• 2015

In this study, the physicochemical characteristics of rice sourdough fermented with Omija extract were investigated. Rice sourdough was made with a 3 stage fermentation process. pH & total titratable acidity, numbers of yeast and lactic acid bacteria, and dough expansion rate were measured. In addition, an RVA was employed to study the pasting properties of rice sourdough. There was a significant (p<0.05) change in both the pH of rice sourdough, which decreased from 5.08 to 3.98, and total titratable acidity, which increased from 0.20 to 0.57 (0.1N NaOH mL), as fermentation time increased. The amount of yeast and lactic acid bacteria significantly increased from 6.73 to 7.65 log CFU/g, 6.93 to 7.65 log CFU/g, respectively(p<0.05). The expansion rate of rice sourdough fermented with Omija extract was higher than rice sourdough fermented without Omija extract. The initial pasting temperatures of rice sourdough fermented with Omija extract were decreased from $91.3^{\circ}C$ to 85.6. The final viscosity and setbacks decreased as fermentation time increased. These results suggest that Omija extract has a beneficial effect on increasing the expansion rate of rice sourdough as a substitute for wheat flour.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.115-126
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• 2007

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.861-869
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• 2015

In this study, wall to bed heat transfer and hydrodynamic characteristics in a conical fluidized bed combustor was investigated using computational fluid dynamics method. A two-fluid Eulerian-Eulerian model was used with applying the kinetic theory for granular flow(KTGF). The effects of the two drag models, Gidaspow and the Syamlal-O'Brien model, different inlet velocities($1.4U_{mf}{\sim}4U_{mf}$) and different particle sizes on the hydrodynamics and heat transfer were studied. The results showed that the hydrodynamic characteristics such as bed expansion ratio and pressure drop were not affected significantly by the drag models. But the heat transfer coefficient was different for the two drag models, especially at lower gas inlet velocities and small particle sizes.

• Korean Journal of Food Science and Technology
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• v.49 no.2
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• pp.168-172
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• 2017

In this study, the fermentative characteristics of rye sourdough fermented with Omija extract were investigated. The pH and total titratable acidity, numbers of yeast and lactic acid bacteria, and expansion rate were measured. While the pH of Omija rye sourdough decreased from 5.60 to 3.86, the total titratable acidity significantly increased from 2.39 to 8.50 with fermentation time (p<0.05). The numbers of yeast and lactic acid bacteria significantly increased for 18 h of fermentation period (p<0.05). The expansion rate of Omija rye sourdough showed a maximum of 183%, more than 47% more than the highest value of rye sourdough (129%). These results suggest that the application of Omija extract for making sourdough could be a good way to decrease the sanitary risk especially for early stage of sourdough fermentation. In addition, Omija rye sourdough could contribute to improvement of baking quality such as volume increase and flavor improvement of rye bread.

• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.437-441
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• 2017

This study was carried out to investigate the volumetric expansion ratio and hardness of expanded graphite after coating with various resins which were used as an additive of fireproof sealant. The coating thickness of the resin, which represents the coating rate, was dependent of the drying speed of the resin and the viscosity of the resin. Therefore the coating thickness was shown as follows: polyvinyl acetate > acrylic resin > urethane resin > water soluble latex. Furthermore, the volumetric expansion ratio was as follows: urethane resin > water soluble latex > acrylic resin > polyinyl acetate and the hardness was as follows: polyvinyl acetate resin > acrylic resin > water soluble latex > urethane resin. This showed that the volume of expansion was reduced by expansion, which was not covered by coating, but significantly increased by increasing hardness and allowed it to be used as a refractory addition. According to the response surface methodology, the optimized addition amount and stirring speed of acrylic resin were 37.6 wt% and 441.4 rpm, respectively.