• Membrane Journal
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• v.23 no.6
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• pp.409-417
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• 2013

Adsorptive permeation hollow fiber membrane (APM) has been developed for effectively separating $CO_2$ from gas mixture. Inside the APM, zeolite 13X particles were uniformly dispersed without covering their surfaces by a symmetric porous structure of polypropylene lattice. In this study, $CO_2/N_2$ mixture was used as a simulated gas mixture. Separation was achieved by adsorbing $CO_2$ on the zeolite particles in the APM and then permeating $N_2$ into permeate side in passing all the feed gas through the APM. Adsorptive permeation tests were carried out with a set of APM modules, and the adsorptive permeation performances of the modules were analyzed from the test results. After saturation of the adsorbent with $CO_2$, the APM was regenerated by desorption of $CO_2$ from it through vacuuming both inside of outside of the APM hollow fiber, and the regeneration process of the APM by vacuuming was discussed in terms of regeneration efficiency and energy consumption.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.35-46
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• 2014

Two types of cast-in-place concrete-filled hollow PC (HPC1, HPC2) columns were developed to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. To form the hollow PC columns, a couple of prefabricated PC panels was used for HPC1, and special hoops were used for HPC2. Lateral pressure of wet concrete on PC faces was measured while placing the concrete inside the columns. To evaluate the seismic resistance, full scale specimens of two HPC columns and a conventional RC column were tested under combined axial compression and lateral cyclic loading. The test results showed that the structural performance of the proposed HPC columns such as intial stiffness, maximum strength, and displacement ductility was comparable to that of the conventional RC column, but the energy dissipation of HPC2 slightly decreased after rebar-buckling. However, all the test specimens satisfied the energy dissipation requirement specified in ACI 374.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.46-55
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• 2016

Three small scale hollow circular reinforced concrete columns(4.5 aspect ratio) were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable are transverse steel ratio. Volumetric ratio of spirals of all the columns is 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The final objectives of this study are to provide quantitative reference data and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, steel fracture, etc. In this paper, describes mainly failure behavior, strength degradation behaviour, displacement ductility of circular reinforced concrete bridge columns with respect to test variables.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.33-40
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• 1988

The new technique has been used to determine the soil-reinforcement interaction. The testing apparatus is essentially a triaxial cell fitted with the capability to house a hollow cylinderical sample. A hollow cylinderical sand specimen with a concentrical layer of reinfarcing material sandwitched in the middle is used in this investigation. The reinforcement is fastened at the base. The hollow specimen can be viewed as a "unit sheet" of a soil-reinforcement composite system of infinite horizontal extent. Axial load as well as inner and outer chamber pressures can be applied to perform a test. The specimen is first subjected to an isotropic stress state corresponding to the overburden pressure. Next, an extension test by reducing the axial load is carried out. The specimen is "loaded" to failure by either the breakage of reinforcing material (tensile failure) or slippage which takes place at the soil-reinforcement interface (i.e. the overcoming of the bonding capacity). Since the reinforcement is fastened at its lower end to the base, any tendency of relative movement between the reinforcement and the sand during an extension test can induce tensile force in the reinforcement thus forming a "reversed pull-out" test condition. Preliminary test results have demonstrated positively of the new approach to test the soil-reinforcement interaction. Reinforcing elements of different extensibility were used to study the deformbility of reinforced soil. Furthermore, both the breakage and the pull-out modes of failure were observed.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.977-984
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• 1996

Liquid-liquid extractions by use of hollow fiber membrane module are fast because of the large surface area per volume. In these membranes, the extractant and feed can be contacted at high speed and two flows are completely independent, so there are no problems with loading and channeling. In this paper, it was investigated the selectivities of extractants for extraction of heavy metals from aqueous solution into organic extractants by using the hollow fiber membrane. To identify the effect of distribution ratio on mass transfer in the membrane, we also compared the distribution ratio with mass transfer coefficient. From these experiments for the system with high distribution ratio, effect of the distribution ratio on mass transfer was weak compare with the low distribution ratio system in the hollow fiber membrane.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.35-46
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• 2012

With the increase in the demand for high-rise buildings, the use of high-strength steel has likewise increased. Thus, it has become more necessary to study the resistance force of the high-strength hollow structural section (HSS) joint of 600MPa. Additionally, the current design equation in Korea limits maximum yield stress at 360MPa in the case of HSS. In other words, since the current specification does not apply to HSS of 600MPa, this study aims to investigate the applicability of design equations as well as examine the behavior of the connection through the experiment and finite element analysis (FEA) of the plate-tube connection of 600MPa. In particular, this paper presents the behavior of joints with the gusset plates welded in the longitudinal direction of the circular hollow section (CHS) when the joints are subjected to lateral force. Comparing design equations with the results of FEA and the test, existing design equations are underestimated to be 56~79% in the case of high-strength materials.

• Journal of the Korean Institute of Gas
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• v.10 no.2 s.31
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• pp.14-21
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• 2006

An experimental apparatus for the removal of $SO_2$ gas using microporous hollow-fiber membrane G-L contactors was setup. Various performance experiments were carried out with commercial membrane modules and the membrane modules made by KIER. The $SO_2$ removal efficiency was outstanding. When the hollow-fiber membrane was used for the removal of $SO_2$, the selection of absorbers and additives, membrane material, operating conditions of membrane manufacture were significant variables to develop optimal G-L contactors. More experiment works will be done for the development of compact, cost-effective and better G-L contactors.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.47-51
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• 2012

In this study, the deformation behavior stability of sealing rings with three different cross sectional areas has been presented using a FEM technique. To investigate the deformation behavior stability, the initial compression rate of 25% has been applied to the sealing ring, which is molded with a nitrile butadiene rubber. The maximum strain, maximum stress, and maximum contact normal stress have been analyzed for the working fluid pressure of $25kgf/cm^2$. The FEM results show that the maximum strain of a hollow o-ring and a hollow rectangular ring with a hollow space in the center of a sealing ring is higher than that of a conventional o-ring, but the maximum stress and the maximum contact normal stress are low. In these results, the sealing rings with a hollow space in the center of the cross sectional area is recommended to increase an extended endurance stability of sealing rings. But, the solid sealing ring is designed to guarantee the sealing safety of a contact sealing ring.

• Journal of Biosystems Engineering
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• v.20 no.4
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• pp.313-322
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• 1995

This study was conducted to find the design factors of spraying device of the boom sprayer for low volume application. Specific objectives of this study were 1) to select proper nozzles for broadcast spraying and row crop spraying by the nozzle spray characterisic experiment, and 2) to investigate the coverage characteristic of rice plant at the row crop spraying. The results of this study are summarized as follows. (1) From the tested results on the droplet diameter spectrum and spray pattern the standard flat-fan nozzle and drift guard nozzle were judged as appropriate for the broadcasting. Even flat-fan nozzle showed similar span values to standard flat-fan nozzles and drift guard nozzle : however, the nozzles were found to be inappropriate for broadcasting because of their spray pattern. Hollow cone nozzle showed relatively small span values and uniform spray pattern. (2) For the upper and lower sides of the rice plants, coverage rates of even flat-fan nozzles and hollow cone nozzles were maximum at the second row, but decreased rapidly after the third row. For the middle side of the rice plants, coverage rates of them were maximum at the first row, but decreased rapidly. When one nozzle was tested, C.V. values were in the range of 90~160% and 60~160% on entire heights of rice plant for even flat-fan nozzles and hollow cone nozzles respectively. C.V. values at other parts were poor. Spray coverage rate at the middle part was improved by overlapping the nozzles whereas there was little difference on the upper and lower part of rice plants. (3) For spraying lower part of rice plant between rows, even flat-fan nozzles and hollow cone nozzle were judged as appropriate, but in order to ensure the uniform coverage, distance between nozzles, recommended to be less than 90cm.

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1670-1679
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• 2015

Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH₄⁺-N/m³/d and 0.10-0.21 kg NO₃^--N/m³/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH₄⁺ or NO₃^- loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.