• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.843-852
• /
• 2005

Presently, test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than $2.0\%$, are scarce. This paper presents test results loaded in axial direction for square reinforced concrete columns confined by various volumetric ratio lateral ties including low-volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type, and tie volumetric ratio. Local strains measured using strain gages bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was efficiently improved by changing tie arrangement type from Type-A to Type-B. A method to compute the stress in lateral ties at the concrete peak strength and a new stress-strain model for the confined concrete are proposed. Over a wide range of confinement parameters, the model shows good agreement with stress-strain relationships established experimentally.

• Tunnel and Underground Space
• /
• v.23 no.1
• /
• pp.66-77
• /
• 2013

This paper deals with Poisson's ratio and volumetric strain behavior on loading-reloading terms under uniaxial condition targeting 404 individual rocks, which include sedimentary rocks as sandstone, shale, mudstone, conglomerate and tuff on Kyungsang basin. Poisson' ratio demonstrates increase, convergence and decrease behavior according to the increase in load, which results in preponderance of increase behavior. Volumetric strain demonstrates normal, positive and negative behavior according to the increase in load, which results in preponderance of normal behavior. On practice, Poisson's ratio can be indicative of high or low values with low values of design load. Consequently, a careful selection of results in in-situ sample experiment should be made and varying design conditions should be considered.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.10 no.1
• /
• pp.65-69
• /
• 1977

The characteristics of two stage compressor which is constituted of two separated reciprocating compressors was tested measuring the volumetric efficiency of each compressor at suction of both bighandlowpressdresideusillgorificetypeflolrmeters. The volumetric efficiency of low pressure side compressor was lower than that of the high side when they were operating under the same compression ratio. And it tended to reduce obviously by lowering evaporating temperature resulting in a markable reduction of refrigerating capacity at the same time. It is assumed that the falling of volumetric efficiency at low side compressor was directed by the decrease in evaporating temperature which derives the falls of gas pressure at suction, increase in compression ratio, and gas flow resistance at suction and discharge valves.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.91-94
• /
• 2005

Experimental research was conducted to investigate the behavior of RC circular columns confined by high-strength ties. Large scale columns with concrete strength 34.1 and 65.3 MPa were tested under monotonically increasing concentric compression. The test parameters included the volumetric ratio, tie arrangement, tie yield strength, and concrete compressive strength. The results indicate that high-strength concrete columns can be confined to achieve inelastic deformations usually predicted for normal-strength concrete columns. This can be done by providing increasing volumetric ratio and tie yield strength.

• Geomechanics and Engineering
• /
• v.33 no.6
• /
• pp.553-565
• /
• 2023

As the structure of broken rock mass is complex, with obvious discontinuity and anisotropy, it is generally necessary to reinforce broken rock mass using grouting in underground construction. The purpose of this study is to experimentally investigate the mechanical properties of broken rock mass after grouting reinforcement with consideration of the characteristics of broken rock mass (i.e., degree of fragmentation and shape) and a range of reinforcement methods such as relative strength ratio between the broken rock mass and cement-based grout stone body (λ), and volumetric block proportion (VBP) representing the volumetric ratio of broken rock mass and the overall cement grout-broken rock mass mixture after the reinforcement. The experimental results show that the strength and deformation of the reinforced broken rock mass is largely determined by relative strength ratio (λ) and VBP. In addition, the enhancement in compressive strength by grouting is more obvious for broken rock mass with spherical shape under a relatively high strength ratio (e.g., λ=2.0), whereas the shape of rock mass has little influence when the strength ratio is low (e.g., λ=0.1). Importantly, the results indicate that columnar splitting failure and inclined shear failure are two typical failure modes of broken rock mass with grouting reinforcement.

• Korean Chemical Engineering Research
• /
• v.55 no.1
• /
• pp.99-106
• /
• 2017

In this study, mixed catalytic char gasification of Indonesia low-rank coal Kideco was investigated under nitrogen atmosphere and isothermal conditions at a fixed reactor. The effects of the temperature were investigated at various temperature (700, 750, 800, $850^{\circ}C$). The effects of blend ratio of catalysts ($K_2CO_3$, Ni) were investigated with different blend ratios (1:9, 3:7, 5:5, 7:3 and 9:1). The sample was prepared by mixing with $K_2CO_3$ physically and by ionexchange method with Ni. The data from thermogravimetric analyzer and gas chromatography were applied to four gassolid reaction kinetic models including shrinking core model, volumetric reaction model, random pore model and modified volumetric reaction model.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.132-135
• /
• 2004

High-performance concrete (HPC) may be expected to differ from usual concrete with respect to shrinkage behavior, and it shows high autogenous shrinkage due to the use of very low water-binder ratio (w/b) and various admixtures. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structure, volumetric change of HPC should be understood. In this study, small prisms made of HPC with w/b of 0.32 and blast-furnace slag content of $0\%,\;30\%,\;and\;50\%$ were prepared to measure the volumetric changes such as autogenous shrinkage, drying shrinkage, and swelling under three different curing conditions. It was observed that the concrete cured. sealed condition showed only autogenous shrinkage while the concrete let to dry condition at temperature of $20^{\circ}C$ and relative humidity of $60\%$ during the test period showed both autogenous and drying shrinkage. Moreover, the concrete exposed to dry condition after 2-day water curing swelled and then started to shrink with age. The total shrinkage (autogenous+drying) of this concrete was smaller than that of the concrete cured dry condition, especially at early-age. Therefore, the early-age moisture curing is very effective to control or minimize the volumetric change and its induced stress of HPC.

• Journal of Hydrogen and New Energy
• /
• v.22 no.6
• /
• pp.772-779
• /
• 2011

New type of syngas generator based on the partial oxidation of biogas in volumetric permeable matrix reformers was suggested as an effective, adaptable and relatively simple way of syngas and hydrogen production for various low-scale applications. The use of biogas as an energy source reduces the chance of possible emission of two greenhouse gases, $CH_4$ and $CO_2$, into the atmosphere at the same time. Its nature of being a reproducible energy source makes its use even more attractive. Parametric screening studies were achieved as air ratio, biogas component ratio, input gas temperature, Steam/Carbon ratio. As the air ratio was low, the production of the hydrogen and carbon monoxide increased in the condition that 3D matrix reformer maintains the stable driving. As it was the simulation biogas in which the carbon dioxide content is high, the flammable range became narrow. And the flammable range was extended if the injected gas was preheated. The stable driving was possible in the low air ratio. The amount of hydrogen production was increased as S/C ratio increased.

• Journal of Environmental Science International
• /
• v.2 no.2
• /
• pp.135-144
• /
• 1993

The purpose of this experimental research was focused to improve the quality of the effluent and the yielded sludge when the papermill wastewater was treated by the indirect aerated submerged biofilter as a second treatment method of papermill wastewater. Changing the various experimental factors (Nutrient additions or not, HRT, Fh ratio, recirculation ratio, etc) with indirect aerated submerged biofilter, the results are as follows. 1) because of the microbes concentration could be sustained to 9, oho man in submerged biofilter and then the volumetric organic loads could be increased to 2.7 kg-BOD/$m^3$<\TEX>/day, the reactor volume can be reduced. 2) Because of the yield coefficient(Y) and the endogenous decay coefficient(kd) were revealed 0.4 and 0.07/d, the yielded sludge volume was reduced. 3) The concentration of the sloughed sludge in the reactor was 2.62~4.01 %, so the thickener could be omited in the papermill wastewater sludge treatment process. 4) When the operating was conducted at HRT of 4hrs, the treatment efficiencies of BOD and COD were obtained 80% and 70%. 5) The range of the theoretical recirculation ratios of this reactor was 14~26. According to those ratios, at the low loads ( BOD volumetric loads is less than 0.79 kg-BOD/$m^3$<\TEX>/day, FM ratio is less than 2.0/d) the results were fitted to the theoretical recirculation ratios (14 ~26) and at the high loads the efficiency were increased to the rise of recirculation ratios.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.19 no.3
• /
• pp.1-9
• /
• 2016

The objective of this study was to exam early stages of plant growth of Euonymus fortunei 'Emerald and Gold' and Hedera japonica grown in fabric felt bag attached on vertical greenery system with the ratio of hydrophilic polymer to substrate, 0(referred as Control), 0.1, 0.2, or 0.4% (v/v), in order to effectively utilize rainfall for low maintenance. After rainfall, the increase in volumetric water content of substrate amended with the hydrophilic polymer was between 13% and 87%, compared to that in Control. During drought period, higher ratio of hydrophilic polymer to substrate slowly decreased the volumetric water content, and increased plant height, leaf length, leaf width, number of leaves, branch number, and stem diameter of both Euonymus fortunei 'Emerald and Gold' and Hedera japonica with the highest fresh and dry weights of shoots or roots under the 0.1% ratio of hydrophilic polymer.