• Journal of Microbiology and Biotechnology
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• v.31 no.10
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• pp.1393-1400
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• 2021

Acetone-butanol-ethanol (ABE) fermentation by the anaerobic bacterium Clostridium acetobutylicum has been considered a promising process of industrial biofuel production. Phosphotransbutyrylase (phosphate butyryltransferase, PTB) plays a crucial role in butyrate metabolism by catalyzing the reversible conversion of butyryl-CoA into butyryl phosphate. Here, we report the crystal structure of PTB from the Clostridial host for ABE fermentation, C. acetobutylicum, (CaPTB) at a 2.9 Å resolution. The overall structure of the CaPTB monomer is quite similar to those of other acyltransferases, with some regional structural differences. The monomeric structure of CaPTB consists of two distinct domains, the N- and C-terminal domains. The active site cleft was formed at the interface between the two domains. Interestingly, the crystal structure of CaPTB contained eight molecules per asymmetric unit, forming an octamer, and the size-exclusion chromatography experiment also suggested that the enzyme exists as an octamer in solution. The structural analysis of CaPTB identifies the substrate binding mode of the enzyme and comparisons with other acyltransferase structures lead us to speculate that the enzyme undergoes a conformational change upon binding of its substrate.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.465-471
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• 2021

Grass breeding starts with the process of selecting grass with good traits, and this operation consumes a lot of resources. Therefore, there is a need for an efficient screening method. Stolon is a unit for the storage of carbohydrates and vegetative propagation, which enhances grass growth and grass sod. Grass varieties with active production of stolons have excellent traits because they reproduce quickly and have a high density. To select grass with such a trait, the survival rate and the production rate of stolon after transplantation of 72 grass germplasms were investigated. After transplantation, the survival rate ranged from 75% to 100%. The majority of the grass cultivars showed a 100% survival rate. Therefore, the group was divided into two groups: A grass variety showing 100% survival and a grass variety that did not show 100% survival. The grass cultivar group, which showed a 100% survival rate after transplantation, included 61 turf varieties, and the rates of stolon production in these grass varieties ranged from 0 to 100%. In contrast, 10 varieties were included in the grass cultivar group that did not show 100% survival after transplantation. These cultivars had a stolon production rate of 0 to 33%. The results suggest that grass germplasms with a 100% survival rate should be selected.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.111-122
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• 2021

Building footprint extraction is an active topic in the domain of remote sensing, since buildings are a fundamental unit of urban areas. Deep convolutional neural networks successfully perform footprint extraction from optical satellite images. However, semantic segmentation produces coarse results in the output, such as blurred and rounded boundaries, which are caused by the use of convolutional layers with large receptive fields and pooling layers. The objective of this study is to generate visually enhanced building objects by directly extracting the vertices of individual buildings by combining instance segmentation and keypoint detection. The target keypoints in building extraction are defined as points of interest based on the local image gradient direction, that is, the vertices of a building polygon. The proposed framework follows a two-stage, top-down approach that is divided into object detection and keypoint estimation. Keypoints between instances are distinguished by merging the rough segmentation masks and the local features of regions of interest. A building polygon is created by grouping the predicted keypoints through a simple geometric method. Our model achieved an F1-score of 0.650 with an mIoU of 62.6 for building footprint extraction using the OpenCitesAI dataset. The results demonstrated that the proposed framework using keypoint estimation exhibited better segmentation performance when compared with Mask R-CNN in terms of both qualitative and quantitative results.

• Korean Journal of Metals and Materials
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• v.47 no.10
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• pp.644-651
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• 2009

The passivation (or deactivation) of a metal surface during oxide film formation has been quantitatively explored for a ferritic stainless steel by using dynamic electrochemical impedance spectroscopy (DEIS). For this purpose, the electrochemical impedance spectra were carefully examined as a function of applied potential in the active nose region of the potentiodynamic polarization curve, to separate the charge transfer resistance and oxide film resistance. From the discrepancy in the potential dependence between the experimental charge transfer resistance and the semi-empirically expected one, the degree of passivation could be quantitatively estimated. The sensitivity of passivation of the steel surface to anodic potential, which might be the measure of the quality of the oxide film formed under unit driving force or over-potential, decreased by 31% when 3.5 wt% NaCl was added to a 5 wt% $H_2SO_4$ solution.

• Journal of the Korean Society of Safety
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• v.36 no.3
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• pp.24-30
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• 2021

Heat is generated during the synthesis and mixing process of chemical compounds due to a change in activation energy during the reaction. A runaway reaction occurs when sufficient heat is not removed during the heat control process within a reactor, rapidly increasing the temperature, reaction speed, and rate of heat generation inside the reactor. A risk assessment was executed using an RC-1 (Reaction Calorimeter) during Friedel-Crafts acylation. Friedel-Crafts acylation runs the risk of rapid heat generation during Active Pharmaceutical Ingredient (API) manufacturing; it was used to confirm the risk of a runaway reaction at each synthesis stage and during the mixing process. This study used experimental data to develop a safety efficiency improvement plan to control the risks of runaway and other exothermic reactions, which was implemented at the production site of a chemical plant.

• Journal of Korea Multimedia Society
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• v.24 no.3
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• pp.355-372
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• 2021

Recently, high-performance HMDs (Head-Mounted Display) are becoming wireless due to the growth of virtual reality technology. Accordingly, environmental constraints on the hardware usage are reduced, enabling multiple users to experience virtual reality within a single space simultaneously. Existing multi-user virtual reality platforms use the user's location tracking and motion sensing technology based on vision sensors and active markers. However, there is a decrease in immersion due to the problem of overlapping markers or frequent matching errors due to the reflected light. Goal of this study is to develop a multi-user virtual reality moving platform in a single space that can resolve sensing errors and user immersion decrease. In order to achieve this goal hybrid sensing technology was developed, which is the convergence of vision sensor technology for position tracking, IMU (Inertial Measurement Unit) sensor motion capture technology and gesture recognition technology based on smart gloves. In addition, integrated safety operation system was developed which does not decrease the immersion but ensures the safety of the users and supports multimodal feedback. A 6 m×6 m×2.4 m test bed was configured to verify the effectiveness of the multi-user virtual reality moving platform for four users.

• Journal of Trauma and Injury
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• v.34 no.4
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• pp.284-287
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• 2021

We report a case of delayed chest wall reconstruction after thoracotomy. A 53-yearold female, a victim of a motor vehicle accident, presented with bilateral multiple rib fractures with flail motion and multiple extrathoracic injuries. Whole-body computed tomography revealed multiple fractures of the bilateral ribs, clavicle, and scapula, and bilateral hemopneumothorax with severe lung contusions. Active hemorrhage was also found in the anterior pelvis, which was treated by angioembolization. The patient was transferred to the surgical intensive care unit for follow-up. We planned to perform surgical stabilization of rib fractures (SSRF) because her lung condition did not seem favorable for general anesthesia. Within a few hours, however, massive hemorrhage (presumably due to coagulopathy) drained through the thoracic drainage catheter. We performed an exploratory thoracotomy in the operating room. We initially planned to perform exploratory thoracotomy and "on the way out" SSRF. In the operating room, the hemorrhage was controlled; however, her condition deteriorated and SSRF could not be completed. SSRF was completed after about a month owing to other medical conditions, and the patient was weaned successfully.

• Current Optics and Photonics
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• v.7 no.3
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• pp.254-262
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• 2023

Novel thermo-optically focus-switchable Fresnel zone plates based on phase-change metafilms are designed and analyzed at a visible wavelength (660 nm). By virtue of the large thermo-optic response of vanadium dioxide (VO₂) thin film, a phase-change material, four different plasmonic phase-change absorbers are numerically designed as actively tunable Gires-Tournois Al-VO₂ metafilms in two and three dimensions. The designed phase-change metafilm unit cells are used as the building blocks of actively focus-switchable Fresnel zone plates with strong focus switching contrast (40%, 83%) and high numerical apertures (1.52, 1.70). The Fresnel zone plates designed in two and three dimensions work as cylindrical and spherical lenses in reflection type, respectively. The coupling between the thermo-optic effect of VO₂ and localized plasmonic resonances in the Al nanostructures offer a large degree of freedom in design and high-contrast focus-switching performance based on largely tunable absorption resonances. The proposed method may have great potential in photothermal and electrothermal active optical devices for nonlinear optics, microscopy, 3D scanning, optical trapping, and holographic displays over a wide spectral range including the visible and infrared regimes.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.389-396
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• 2005

Despite very good reputation that Korean construction industrial firms had enjoyed until early 1990's in overseas markets, their participation abroad drastically declined after the delivery of two(2) million unit-housing project in the early 1990's and the foreign currency crisis that took place in the late 1990's. The revival of booming construction industry in domestic market is far beyond the expectation due to the long recession of the construction economy and government's severe restriction against real estate development. Under such crucial circumstances, the construction industrial firms' strategy to survive is the more active business promotion in overseas markets. However, the Korean construction industrial firms have to abandon the labor intensive strategy, through that they have enjoyed until the early 1990's, and turn to management oriented strategy which may be a new prosperous horizon and a new challenge as well, because the labor cost of newly developing countries is much more competitive. The aim of this study is to suggest how to cope with current market situations through a chronological survey based on the cost data prevailed during four decades from the 1960's until the 1990's in overseas markets.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.4
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• pp.206-214
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• 2023

Tungsten carbide has many industrial applications due to its high electrical and thermal conductivity, high melting temperature, high hardness and good chemical stability. Because tungsten carbide is difficult to sinter, it is sintered with nickel or cobalt as a binder and is currently used in nozzles, cutting tools, and molds. Alumina is reported to be a viable binder for tungsten carbide due to its higher oxidation resistance and lower cost than nickel and cobalt. The ultrafine tungsten carbide-graphene-alumina composites were rapidly sintered in a high frequency induction heating active sintering unit. The microstructure and mechanical properties (fracture toughness and hardness) of the composites were investigated and analyzed by Vickers hardness tester and electron microscope. Since the high-frequency induction heating sintering method enables high-speed sintering, ultrafine composites can be prepared by preventing grain growth. In the tungsten carbide-graphene-alumina composites, the grain size of tungsten carbide increased with the amount of alumina participation. The hardness and fracture toughness of the tungsten carbide-5% graphene- x% alumina (x = 0, 5, 10,15) composites were 5.1, 8.6, 8.6, and 8.4 MPa-m^1/2 and 2384, 2168, 2165, and 2102 kg/mm², respectively. The fracture toughness increased without a significant decrease in hardness. Sinterability was improved by adding alumina to tungsten carbide-graphene.