• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.87-95
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• 2023

Recently, redevelopment of the original downtown area is underway, the necessity of construction in adjacent location is increasing. However, excavations in dense urban areas are prone to ground problems due to various causes, so it is necessary to use materials and methods that can minimize such problems. As a general earth retaining method, various methods such as diaphragm wall and CIP method are applied using cement. However, since a large amount of cement is used for the installation of earth retaining method, it is necessary to conduct research on the development of new cement substitute materials to significantly reduce greenhouse gas emissions. In this study, we utilized the hardening reaction of blast furnace slag powder, desulfurized gypsum and high calcium fly ash by alkali activation and applied it to the SCW method. As a result, it was analyzed that the compressive strength of solidified soil using development solidification material was 96.2 ~ 106.3% of OPC at 28 days of curing. In addition, the strength increment ratio was 2.06 for sandy soil and 2.41 for clayey soil, which was higher than 1.85 of OPC. It seems an advantageous in terms of long-term strength. In addition, from the environmental point of view, it was analyzed that there is no elution of heavy metals and that greenhouse gas emissions can be dramatically reduced. Therefore, if further studies are conducted, it can be applied to the SCW method.

• Clean Technology
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• v.15 no.4
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• pp.273-279
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• 2009

$SF_6$, which has a high global warming potential, can be decomposed to sulfur and fluorine compounds through hydrolysis by $H_2O$ or oxidation by $O_2$ over solid acid catalysts. In this study ${\gamma}-Al_2O_3$ was employed as the solid acid catalyst for the abatement of $SF_6$ and its catalytic activity was investigated with respect to the reaction temperature and the space velocity. The catalytic activity for $SF_6$ decomposition by the hydrolysis reached the maximum at and above 973 K with the space velocity of $20,000\;ml/g_{-cat}{\cdot}h$, exhibiting a conversion very close to 100%. When the space velocity was lower than $45,000\;ml/g_{-cat}{\cdot}h$, the conversion was maintained at the maximum value. On the other hand, the conversion of $SF_6$ by the oxidation was about 20% under the same conditions. The SEM and XRD analyses revealed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during the hydrolysis and to $AlF_3$ during the oxidation, respectively. The size of $AlF_3$ after the oxidation was over $20\;{\mu}m$, and its catalytic activity was low due to the low surface area. Therefore, it was concluded that the hydrolysis over ${\gamma}-Al_2O_3$ was much more favorable than the oxidation for the catalytic decomposition of $SF_6$.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.285-290
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• 2023

Poly-lactic acid (PLA) is the most promising polymer in additive manufacturing as an alternative to acrylonitrile butadiene styrene (ABS). Since it is produced from renewable resources such as corn starch and sugar beets, it is also biocompatible and biodegradable. However, PLA has a couple of issues that limit its use. First, it has a comparatively low glass transition temperature of around 60 ℃, such that it exhibits low thermal resistance. Second, PLA has low impact strength because it is brittle. Due to these problems, scientists have found methods to improve the crystallinity and ductility of PLA. Polyethylene glycol (PEG) is one of the most studied plasticizers for PLA to give it chain mobility. However, the blend of PLA and PEG becomes unstable, and phase separation occurs even at room temperature as PEG is self-crystallized. Thus, it is necessary to investigate the optimal mixing ratio of PLA-PEG at the molecular scale. In this study, molecular dynamics will be conducted with various ratios of L-type PLA (PLLA) or DL-type PLA-PEG (PDLA-PEG) systems by using BIOVIA Materials Studio.

• Composites Research
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• v.19 no.1
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• pp.29-35
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• 2006

The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

• Journal of Appropriate Technology
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• v.5 no.1
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• pp.18-24
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• 2019

Citarum river in West Java, Indonesia plays strategic roles for Jakarta metropolitan areas. Besides it provides major source of water supply such as domestics and drinking water including Jakarta, it also provides water for hundreds of industries through its cascade reservoirs. However, recently, Citarum river basin has been seriously suffering from water and groundwater pollution as well as the lowering-down of groundwater level due to the extreme use of water resources in dry season by domestic and industrial activities. This project objectives are design and installation of industrial wastewater treatment/recycle facilities to overcome the problem of water pollution and the lowering-down of groundwater level in Bandung. For these, cyclone type dissolved air flotation (DAF), CYFLOAT, was successfully installed as the appropriate technology for the target textile industry with 100 ton/day of capacity. The CYFLOAT system can remove the 96.8% of particulates, which are known as a critical factor to recycle the wastewater, within 40 min of residence time. Furthermore, The CYFLOAT system can reduce the operational cost and land use. The project was carried out in strong partnership with local institute including UNPAR, IBT, and PUSKIM for the sustainability of the technology to textile industry complex in Indonesia.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.221-230
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• 2009

In Korea, many water intake plants are easily affected by effluents of sewage treatment plants because sewage treatment plants are usually located upstream or nearby the plants of the same riverine area. Furthermore, the inflow of harmful contaminants owing to pollutant spills or transportation accidents of vehicles using the roads and bridges intersecting the river causes significant impact on the management of water intake plants. Paldang lake, the main water intake plants in Korea, is especially exposed to various water pollution accidents, because the drainage basin area is significantly large compared to the water surface area of the lake. Therefore it is necessary to predict the possible pollutant spill in advance and consider measurements in case of water pollution. In this study, water quality prediction was performed in Paldang Lake in Korea durig the dry season using two-dimensional numerical models. In order to represent the cases of pollutant accidents, the difference of pollutant transport patterns with varying injection points was analyzed. Numerical simulations for hydrodynamics of water flow and water quality predictions were performed using RMA-2 and RAM4 respectively. As a result of simulation, the difference of pollutant transport with the injection points was analyzed. As a countermeasure against the pollutant accident, the augmentation of the flow rate is proposed. In comparison with the present state, the rapid dilution and flushing effects on the pollutant cloud could be expected with increase of flow rate. Thus, increase of flow rate can be used for operation of water intake plants in case of pollutant spill accidents.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.78-82
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• 2023

A fabrication of smart windows with controllable visible light transmittance in three steps by using λ/2 retardation films based on a reactive mesogen (RM) material and polarizing films is demonstrated. The phase retardation films with a Δn·d value of λ/2 (λ: wavelength) convert the direction of a traveling light to the optical axis of the film symmetrically. In this work, the retardation characteristics according to the RM thickness were evaluated and henceλ/2 phase retardation film can be fabricated. The phase retardation film with Δn·d of 276.1 nm, which is close to λ/2 (=275 nm @550 nm), was fabricated. The light transmittance of a smart window with the structure of (polarizing film)/(glass)/(alignment layer)/(λ/2 retardation film) was measured in the transmission mode, half mode and blocking mode. The evaluation results show that the transmittance of the smart window can be controlled in three steps with 35.8%, 27.8%, and 18.2% at each mode, respectively. In addition, by fabricating a smart window with a size of 15×200 mm², the feasibility of use in various fields such as buildings and automobiles was verified.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.59-71
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• 2023

Carbon capture, and storage (CCS) is important for the reduction of greenhouse gases and achieving carbon neutrality. CCS focuses on storing captured CO₂ permanently in underground reservoirs. CO₂-enhanced oil recovery (CO₂-EOR) is one form of CCS, where CO₂ is injected into the underground to enhance oil recovery. CO₂-EOR not only aids in the extraction of residual oil but also contributes to carbon neutrality by storing CO₂ underground continuously. CO₂-EOR can be classified into miscible and immiscible methods, with the CO₂-water alternating gas (CO₂-WAG) technique being a representative approach within the miscible method. In CO₂-WAG, water and CO₂ are alternately injected into the reservoir, enabling oil production and CO₂ storage. The WAG method allows for controlling the breakthrough of injection fluids, providing advantages in oil recovery. It also induces hysteresis in relative permeability during the injection and production process, expanding the amount of trapped CO₂. In this study, the effects of enhancing oil recovery and storing CO₂ underground during CO₂-EOR were presented. Additionally, cases of CO₂-EOR application in relation to CCS were introduced.

• Resources Recycling
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• v.32 no.6
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• pp.45-53
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• 2023

This study discussed the trend and future strategy of adsorption technology R&D to effectively recover ammonia emitted from the livestock fields. A proper ammonia adsorbent should incorporate acidic or hydrogen bonding functional groups on the surface, as well as a high specific surface area and a good surface structure appropriate for ammonia adsorption. Activated carbon and minerals such as zeolite have widely been used as ammonia adsorbents, but their adsorption effects are generally low, so any improvement through surface modification should be necessary. For example, incorporation of metal chloride included in a porous adsorbent can promote ammonia adsorption effectiveness. Recently, new types of adsorbents such as MOFs (Metal-Organic Frameworks) and POPs (Porous Organic Polymers) have been developed and utilized. They have shown very high ammonia adsorption capacity because of adjustable and high specific surface area and porosity. In addition, Prussian Blue exhibited high ammonia adsorption and desorption performance and selectivity. This looks relatively advantageous in relation to the recovery of ammonia from livestock waste discharge. In the future, further research should be made to evaluate ammonia adsorption/desorption efficiency and purity using various adsorbents under conditions suitable for livestock sites. Also, effective pre- and/or post-treatment processes should be integrated to maximize ammonia recovery.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.80-80
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• 2022

본 연구에서는 남부지역 논의 이모작 작부체계로부터 생산한 국산밀의 품질 특성을 살펴보았다. 벼 및 이의 대체작물(검정콩, 참깨, 들깨)과 연계한 작부체계별로 생산된 국산밀의 제분율은 모든 토양에서 70% 이상으로 높았으며, 밀가루의 색상은 전작 작물의 종류에 따라 색도(L^*, a^*, b^*) 값과 백색도 지수가 변화하였다. 특히, 흰색의 정도를 나타내는 L^*값과 백색도는 벼 전작 토양에서 수확한 밀에서 높았다. 그러나 다량 및 미량 영양소 함량은 벼 전작물 토양에서 수확된 밀에서 낮았고 대체 작물을 전작한 토양에서 생산한 밀에서 대체로 높았다. 다량 영양소 중 P와 Mg의 함량과 미량 영양소 중 Zn와 Cu의 함량은 검정콩을 전작한 토양에서 수확한 밀에서 특히 높았다. 국산밀의 회분, 단백질, 아밀로스와 손상전분 함량은 각각 0.45-0.59%, 7.7-9.5%, 22.3-24.0%와 5.0-5.9%이다. 국산밀 중에 조경밀은 단백질 함량이 다른 품종에 비해 높고 질이 우수하여 제빵용으로 이용되고 있는데, 본 연구에서는 작부체계에 관계없이 전체적으로 10% 이하로 낮은 특성을 보였다. 그나마 검정콩을 전작한 토양에서 수확한 밀에서 9.45%이며, 벼를 전작한 토양에서는 8.0% 이하로 극히 낮았다. 또한 SDS-침전가도 검정콩 전작 토양에서 수확한 밀에서 높았으며, 회분 함량은 0.6% 이하로 1등급에 해당되었다. 논토양에서 참깨나 콩, 들깨 등의 벼 대체 작물들의 전작은 토양의 물리화학적 특성을 개선하고 제빵공정에 좀 더 유리한 고품질의 밀을 생산하는 데 이바지할 수 있음을 보여준다. 그러나 검정콩-밀 작부체계의 생육일수(344일)가 벼-밀(331일), 들깨-밀(337일), 참깨-밀(310일) 보다 길어 앞뒤 작물의 작기 연결성에 있어서 여유가 없었으며, 기상환경의 변화에 따라 검정콩의 수확시기가 늦어지게 되면 밀 파종 시기와 겹칠 수 있는 우려가 있다. 차후에 시비 기준을 달리한 조건에서 밀의 생산성 증대와 더불어 최고 품질의 밀을 생산할 수 있는 체계를 확립하고자 한다.