• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.53-62
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• 2007

This paper presents a new vibration control method for long-span bridges using complex damper system. The new system presents simple mechanical configuration with oil and elasto-plastic dampers which have velocity and displacement dependency in vibration energy absorbing. This system can produce various damping forces according to the applied external forces by the velocity and displacement-dependent characteristics of the dampers. The oil damper dissipates vibration energy for relatively frequent and small amplitude like in the case for small to moderate earthquakes, whereas the elasto-plastic damper system works for rare and large amplitude vibration such as high seismic excitation. Thus, the proposed system exhibits the advantage of low cost with high performance since the roles of the two different dampers are effectively separated. A numerical model is established for the complex damper system, and the response characteristics and effectiveness of the proposed system are presented through numerical simulations. Numerical results show that the proposed complex damper system can significantly improve the seismic performance of long-span bridge structures with much more effective damping mechanism than single conventional passive damper systems.

• Clean Technology
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• v.20 no.2
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• pp.103-107
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• 2014

Acrylic acid is a commodity chemical which is applicable for various industries such as polymer and textile industry. Currently, it has been produced by chemical synthesis from petroleum. However, due to the high price of petroleum and global $CO_2$ emission, renewable materials such as sugar are interesting alternative carbon sources for the biological production of acrylic acid. For an economic production of acrylic acid from renewable carbon sources, a cost effective separation process for acrylic acid should be needed. In this study, reactive extraction by TOA (tri-n-octylamine) was used for the recovery of acrylic acid from its aqueous solutions. The effects of polarity of diluents and concentration of TOA on extraction equilibrium were investigated. The extraction efficiency was proportional to concentration of TOA and polarity of diluents and its value was more than 95% in the case of sufficient concentration of TOA. From IR spectroscopy, it was concluded that the ratio of (1,1) acid-amine complex was increased and the ratio of acid dimer was decreased with concentration of TOA. Equilibrium model based on IR spectroscopy was well fitted with experimental data.

• Clean Technology
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• v.24 no.1
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• pp.27-34
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• 2018

Catalytic filter has many advantages for the industrial application owing to its bi-functional ability to treat nitrogen oxides and particulate simultaneously. The technical feasibility of using the catalytic filter in the flue gas treatment process will be more promoted if the high porous ceramic sheet filter is utilized. However, it is not easy to prepare the effective catalytic filter using sheet filter as it has less room for catalyst support due to its thin layer. In this study, catalytic filter using a domestic ceramic sheet filter element has been prepared and conducted the experimental evaluation for NO reduction performance. The current sheet filter element shows the low catalytic activity less than 92% conversion for NO concentration 700 ppm at the face velocity $0.02m\;s^{-1}$. This unexpected low catalytic activity seems to be caused by the present of extraordinary large pores from the lack of uniformity in the pore size distribution of the sheet filter. The large pore size of the sheet filter is reduced by composing the smaller powder as its raw material, which presents improvement in NO conversion more than 96%. More improvement is observed showing 98% NO conversion which is applicable to a commercial plant when the catalyst coating layer is expanded by adding the large $TiO_2$ particles during the catalyst preparation. Both of above two methods is regarded as that the broad gates of the larger pores in the coating layer are effectively filled with the proper catalyst. So these results encourage the utilization of sheet filter as a good catalytic filter material with its potential merit of high permeability.

• Polymer(Korea)
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• v.38 no.6
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• pp.752-759
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• 2014

Crosslinked polyimides (PIs) were synthesized by reacting 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFDB) with various ratios of the cross-linkable, end-capping agent cis-1,2,3,6-tetrahydrophthalic anhydride (CDBA) via ring-opening metathesis polymerization. Residual stress behaviors were investigated in-situ during thermal imidization of the crosslinked PI precursors using a thin film stress analyzer (TFSA) by wafer bending method. The thermal properties were investigated via differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA). The optical properties were measured by ultraviolet-visible spectrophotometer (UV-vis) and spectrophotometry. All properties were interpreted with respect to their morphology of crosslinked networks. With increasing the amounts of the end-capping agent, the residual stress decreased from 27.9 to -1.3 MPa, exhibited ultra-low stress and high thermal properties. The minimized residual stress and enhanced thermal properties of the crosslinked PI makes them potential candidates for versatile high-density multi-layer structure applications.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1017-1026
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• 2014

To investigate the effect of upstream dam operation and river water use on the downstream flows, SWAT-K watershed model was applied to the Paldang Dam watershed of the Han River basin. Analysis results from 2001 to 2009 showed that outflows from the multi-purpose dams such as the Soyanggang Dam and Chungju Dam much have a strong influence on the downstream flows during both the low- and high-flow seasons. This resulted an increase of low-flow at the Paldang Dam, the end of Pukhangang, and the Yangpyeong stage station by $100.57m^3/s$, $33.01m^3/s$, and $49.66m^3/s$, respectively. Whereas, the impact of river water use was hardly found in the Pukhangang, and also was not significant in the (Nam)hangang. Therefore, the effect of small dam such as the Hoengseong Dam or river water use would be able be excluded for long-term runoff analysis. But, in the case of the areas with a large amount of water use, a sufficient information such water-intake and water movement also must be taken into account like this study.

• Korean Journal of Food Science and Technology
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• v.36 no.2
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• pp.288-293
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• 2004

Differential scanning calorimetry (DSC) was used to study effects of sucrose and gluten on wheat starch glass transition, gelatinization, and retrogradation. Glass transition temperature ($T_{g}$) of wheat starch decreased as the ratio of sucrose or gluten to starch increased. Both peak temperature ($T_{G}$) and enthalpy values of gelatinization endotherm increased or decreased with increasing ratio of sucrose or gluten, respectively. Wheat starch gel with no sucrose and gluten recrystallized up to 4 weeks of storage at $4^{\circ}C$, whereas those with sucrose and gluten completed recrystallization within 1 week. Both wheat starch gels with no sucrose and gluten, and those with sucrose and gluten at storage temperature of $32^{\circ}C$ recrystallized up to 4 weeks, with wheat starch-sucrose-gluten (1 : 0.5 : 0.12) system, which had highest ratios of gluten and sucrose to starch, showing lowest recrystallization. Nucleation and propagation rates of starch gel recrystallization based on polymer crystallization principles can be converted into peak width (${\delta}T$) and peak temperature ($T_{R}$) of retrogradative endotherm by DSC, because higher nucleation rate at storage temperature of $4^{\circ}C$ close to $T_{g}$ showed higher ${\delta}T$, whereas higher propagation rate at $32^{\circ}C$ (close to $T_{G}$) had higher $T_{R}$.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.88-93
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• 2005

Anode-supported solid oxide fuel cell (SOFC) was investigated to increase the cell power density at intermediate temperature through control of the cathode structure. The anode-supported SOFC cell were fabricated by wet process, in which the electrolyte of $8mol\%\;Y_2O_3-stabilized\;ZrO_2 (YSZ)$ was coated on the surface of anode support of Ni/YSA and then the cathode was coated. The cathode has two- or three- layered structure composed of $(La_{0.85}Sr_{0.15})_{0.9}MnO_{3-x}(LSM),\;LSM/YS$ composite (LY), and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3{LSCF)$ with different thickness. Their single cells with different cathode structures were characterized by measuring the cell performance and ac impedance in the temperature range of 600 to $800^{\circ}C$ in humidified hydrogen with $3\%$ water and air. The cell with $LY\;9{\mu}m/LSM\;9{\mu}m/LSCF\;17{\mu}m$ showed best performance of $590mW/cm^2$, which was attributed to low polarization resistance due to LY and to low interfacial resistance due to LSCF.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.69-73
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• 2010

Finite-element analyses were conducted to investigate the thermal stress in 3-dimensional stacked wafers package containing through-silicon-via (TSV), which is being widely used for 3-Dimensional integration. With finite element method (FEM), thermal stress was analyzed with the variation of TSV diameter, bonding diameter, pitch and TSV height. It was revealed that the maximum von Mises stresses occurred at the edge of top interface between Cu TSV and Si and the Si to Si bonding site. As TSV diameter increased, the von Mises stress at the edge of TSV increased. As bonding diameter increased, the von Mises stress at Si to Si bonding site increased. As pitch increased, the von Mises stress at Si to Si bonding site increased. The TSV height did not affect the von Mises stress. Therefore, it is expected that smaller Cu TSV diameter and pitch will ensure mechanical reliability because of the smaller chance of plastic deformation and crack initiation.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.3
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• pp.1-17
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• 2016

The main aim of this study is to provide an overview of the characteristics the Oungak (五雲閣) area on the north of rear garden of Gyeongbokgung Palace which was constructed during the time of king Kojong. This study also consider the aspect of functional elements of Ocryucheon (玉流川) located in Changdeokgung Palace and how the Oungak area was used as a substitute for the Ocryucheon. The Oungak area is the private space of the king. It was built in a natural setting which used existing environment including spring water and the rock carved with inscriptions 'Cheonha-Jaeil-Bokji (天下第一福地). King Kojong tried to replace Ocryucheon with Oungak area which had played a important role of relaxation and leisure for royal family at the Ocryucheon to reconstructed Gyeongbokgung Palace. Despite being away from each other, Oungak area seems quite similar to Ocryucheon area. Oungak area and Ocryucheon have a common conditions of a location and structure of the building. Both constructed on the northernmost part of rear garden, composition of buildings and the design of waterway estimated to function as Curve-Stream Banquet. Oungak area was consisted of Ocryeonjeong (玉蓮亭) Pavilion, Oungak Building, Byeokhwasil (碧華室) Building and Cheonha-Jaeil-Bokji-Cheon (天下第一福地泉) Spring and Streams. Except Byeokhwasil Building, spatial compositions of Oungak area showed pattern that were similar to Ocryucheon area. The area was developed, moreover, to unconventional space that depended on the conditions of topography, slope, water system. First, The Ocryeonjeong Pavilion constructed to view the landscape of Seoul to Namsan Mountain. Second, the peculiar form of Cheonha-Jaeil-Bokji-Cheon Streams is estimated the shape imitated from Curve-Stream Banquet on Ocryuchon. Third, Oungak Building was constructed like a habitable house with Nongsanjeong Building in Ocryucheon. The Oungak area was constructed to improve Gyeongbokgung Palace, Consequently, the Oungak area specially characteristic of Joseon palaces's rear garden.