• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.85-91
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• 2023

In this study, an experimental study was conducted on the flame behavior, combustion dynamics, and NOx emission characteristics for hydrogen co-firing with the EV burner which is the first stage combustor of GT24. It was confirmed that as the hydrogen co-firing rate increases, the NOx emission increases. This change was elucidate to be the result of a combination of changes in penetration depth due to changes in fuel density, reduction in fuel mixing due to changes in flame position due to increased flame propagation speed, and oscillation of fuel mixedness due to combustion instability. Through pressurization tests in the range of 1.3 to 3.1 bar, NOx emission characteristics under high-pressure operating conditions were predicted, and based on this, the hydrogen co-firing limits of the EV burner was evaluated.

• Information Systems Review
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• v.24 no.4
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• pp.41-54
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• 2022

Despite the recent rapid advancement of science and technology, we have been experiencing the decline in productivity since the 2000s. This study aims to investigate the decline at both industry and firm levels, by looking at the emergence and growth of large firms such as Amazon, Alphabet, and Apple and M&A trends. Following the results of previous studies, our results show that productivity at industry level has decreased since the 2000s. Particularly, in the period after 2011, the deterioration of allocative efficiency due to the large firms and the decline in the growth rate of surviving firms in the industry with low ratio of large firms contributed to the productivity decline. On the other hand, our analysis at firm level demonstrates that the productivity of firms that acquired IT firms improved over the entire period. While M&As have a positive impact on productivity, M&As with a demand-side motive such as market penetration and expansion of channels have a relatively larger impact than the ones for production or operation efficiency. Our results also suggest that the higher the proportion of large firms in a specific industry, the lower the productivity of individual firms in the same industry. Overall, given that the industry's structural changes for digital transformation tends to strengthen the growth of large firms, our findings have significant implications by empirically identifying the relationships of the emergence of large firms, the acquisition of IT/Non-IT firms, and motivations for M&As to firm/industry productivity.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.2
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• pp.157-172
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• 2024

Autonomous driving technology, when commercialized, has the potential to improve the safety, mobility, and environmental performance of transportation networks. However, safe autonomous driving may be hindered by poor sensor performance and limitations in long-distance detection. Therefore, cooperative autonomous driving that can supplement information collected from surrounding vehicles and infrastructure is essential. In addition, since HDVs, AVs, and CAVs have different ranges of perceivable information and different response protocols, countermeasures are needed for mixed traffic that occur during the transition period of autonomous driving technology. There is a lack of research on traffic flow optimization that considers the penetration rate of autonomous vehicles and the different characteristics of each road segment. The objective of this study is to develop weights based on safety, operational, and environmental factors for each infrastructure control use case and autonomous vehicle MPR. To develop an integrated evaluation index, infra-guidance AHP and hybrid AHP weights were combined. Based on the results of this study, it can be used to give right of way to each vehicle to optimize mixed traffic.

• Information Systems Review
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• v.22 no.1
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• pp.125-146
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• 2020

With the penetration of the Internet and e-commerce, a 'crowdfunding' has emerged as a new way of financing. Crowdfunding has the advantage for a person to able to a simple way to finance her/his an innovative product or service from crowd. However, the success rate for crowdfunding projects is less than half. In this study, we introduce social exchange theory to explore the impact of trust and perceived psychological risk on the intention to participate in a crowdfunding website. Different from previous studies that have focused on a crowdfunding creator, we consider two different perspectives of a project creator and a project supporter. In addition, we compare perceptions of crowdfunding in different cultural contexts by conducting survey in two different countries Korea and Austria. Result shows that trust in recommendation and trust in website have different impacts on the intention to participate from two different perspectives. It also shows that perception of the quality and transparency of information provided by crowdfunding website has greater impact on trust in Korea than that in Austria. In case of perception of psychological risk, it has a negative impact on Austria's intention to create or support a project. On the other hand, it has relatively small impact on the intention to support and does not affect the intention to create a project in Korea.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.12-23
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• 2024

In this study, a structural concrete square beam was developed using the centrifugal molding technique. In order to secure the bending stiffness of the cross section, the hollow rate of the cross section was set to 10% or less. Instead of using the current poor mixture of concrete and a concrete mixing ratio with a high slump (150-200) and a design strength of 100 MPa or more was developed and applied. In order to investigate the durability of centrifugally formed PSC square beams to be used as the superstructure of the avalanch tunnel or ramen bridge, the durability performance of ultra-high-strength centrifugally formed concrete with a compressive strength of 100 MPa was evaluated in terms of deterioration and chemical resistance properties.Concrete durability tests, including chloride penetration resistance, accelerated carbonation, sulfate erosion resistance, freeze-thaw resistance, and scaling resistance, were performed on centrifugally formed square beam test specimens produced in 2022 and 2023. Considering the information verified in this study, the durability of centrifugally molded concrete, which has increased watertightness in the later manufacturing stage, was found to be superior to that of general concrete.

• Journal of the Korean Society of Radiology
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• v.84 no.4
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• pp.879-888
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• 2023

Purpose The present study was to evaluate the outcomes of Denali filter retrieval. Materials and Methods We retrospectively reviewed 143 patients who received Denali filter insertion from September 2015 to April 2020. Ninety-seven patients who required removal of the filters were include in this study. Filters were retrieved with either standard or advanced techniques. Venography before and after retrieval was obtained to evaluate technical success, complications and duration of filter insertion. Results All 97 filters were retrieved successfully without complications. Ninety-two (94.8%) were retrieved with standard technique and 5 filters (5.2%) required the advanced technique. There were two cases with a filter angle greater than 15 degrees. Inferior vena cava penetration was shown in 17 patients (17.5%) on venography but was not associated with contrast media extravasation after filter removal. Conclusion The Denali filter showed a high rate of successful retrieval without complications. This study adds value to previous studies and trials showing that the Denali filter is a reliable and safe filter that can potentially improve retrieval rates, with increasing use of this device.

• Clean Technology
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• v.27 no.4
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• pp.359-366
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• 2021

Halloysite nanotubes (HNTs), the multiwalled clay mineral with the composition of Al₂Si₂O₅(OH)₄·nH₂O, have been highlighted as a low-cost adsorbent for the removal of dyes from wastewater. Although a powder of halloysite presents a high specific surface area, forming media are significantly considered due to sludge-clogging induced by the water-bound agglomeration. However, higher firing temperature to achieve the structural durability of the media and lower utilization rate due to longer penetration depth into the media act as hurdles to increase the dye-adsorption capacity. In this work, the retention of the adsorption capacity of halloysite was evaluated with methylene blue solution after the heat treatment at 750 ℃. In order to improve the utilization rate, tubular media were fabricated by extrusion. The images taken by transmission electron microscopy show that HNTs present excellent structural stability under heat treatment. The HNTs also provide superb capacity retention for MB adsorption (93%, 18.5 mg g^-1), while the diatomite and Magnesol^® XL show 22% (7.65 mg g^-1) and 6% (11.7 mg g^-1), respectively. Additionally, compositing with lignin enhances adsorption capacity, and the heat treatment under the hydrogen atmosphere accelerates the adsorption in the early stage. Compared to the rod-type, the tubular halloysite media rapidly increases methylene blue adsorption capacity.

• Journal of the Korean Applied Science and Technology
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• v.41 no.1
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• pp.9-18
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• 2024

Smilax china is known for its excellent antimicrobial, antioxidant, and anti-inflammatory properties. As a foundational study for applying the functionality of Smilax china extracts to cosmetics, it is necessory to investigate the concentration-dependent skin permation characteristics of the flavonoids in the extract, namely quercetin, catechin, and naringenin. Therefore, it serves as a crucial method for conducting this basic research on the functional aspects fo Smilax china extracts for cosmetic applications. This investigation focused on examining the percutaneous permeability characteristics of flavonoids originating from Smilax china. Applying Marzulli's definition, the Kp value of quercetin was categorized as "fast" at 0.1 mg/mL and "moderate" at 0.2 and 0.4 mg/mL. Notably, the permeation rate exhibited a decline with increasing concentration. For naringenin, Flux values were 0.69, 1.07, and 1.42 ㎍/hr/cm² at concentrations of 0.1, 0.2, and 0.4 mg/mL, respectively, with corresponding Kp values of 6.95, 5.34, and 3.56. Naringenin's Kp value fell into the "moderate" category across all concentrations, and as observed with quercetin, the permeation rate decreased with higher concentrations. Likewise, for catechin, Flux values were 0.75, 1.09, and 1.66 ㎍/hr/cm², and corresponding Kp values were 7.55, 5.46, and 4.16. Catechin's Kp value was consistently classified as "moderate" across all concentrations. The efficacy of quercetin, catechin, and naringenin, active ingredients in high-performance and anti-inflammatory Smilax china extracts, was found to exhibit skin penetration properties above the average. This confirms their suitability as excellent natural materials for use in functional cosmetics, given their outstanding capabilities in preventing acne and reducing inflammation.

• Journal of Korean Society of Forest Science
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• v.82 no.2
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• pp.152-165
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• 1993

This is the basic study in order to know the amount of transpirational water loss in a Larix leptorepis stand by a heat pulse method. Especially this study has been measured and discussed the diurnal and seasonal trends of heat pulse velocity by changes of radiation, temperature and humidity, differences of heat pulse velocity by direction and depth in stem, differences of heat pulse velocity by dominant, codominant and suppressed trees, diurnal change of heat pulse velocity by change of leaf water potential, sap flow path way in sapwood by dye penetration and amount of daily and annual transpiration in a tree and stand. The results obtained as follows : 1. Relation between heat pulse velocity(V) and sap flow rate(SFR) was established as a equation of SFR=1.37V($r=0.96^{**}$). 2. The sap flow rate presented in the order of dominant, codominant and suppressed tree, respectively. The daily heat pulse velocity was changed by radiation, temperature and vapor pressure deficit. 3. The heat pulse velocity in individual trees did not differ in early morning and in late night, but had some differed from 12 to 16 hours when radiation was relatively high. 4. The heat pulse velocity and leaf water potential showed similar diurnal variation. 5. The seasonal variation of heat pulse velocity was highest in August, but lowest in October and similar value of heat pulse velocity in the other months. 6. The heat pulse velocity in stem by direction was highest in eastern, but lowest in southern and similar velocity in western and northern. 7. The difference of heat pulse velocity in according to depths was highest in 2.0cm depth, medium in 1.0cm depth, and lowest in 3.0cm depth from surface of stem. 8. The sap flow path way in stem showed spiral ascent turning right pattern in five sample trees, especially showed little spiral ascent turning right in lower part than 3m hight above ground, but very speedy in higher than 3m hight. 9. The amount of sap flow(SF) was presented as a equation of SF=1.37AV and especially SF in dominant tree was larger than in codominant or suppressed tree. 10. The amount of daily transpiration was 30.8ton/ha/day and its composition ratio was 83% at day and 17% at night. 11. The amount of stand transpiration per month was largest in August(1,194ton/ha/month), lowest in May (386ton/ha/month). The amount of stand transpiration per year was 3,983ton/ha/year.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.67-76
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• 2013

Landfill require special care due to the dangers of nearby surface water and underground water pollution caused by leakage of leachate. The leachate does not leak due to the installation of the geomembrane but sharp wastes or landfill equipment can damage the geomembrane and therefore a means of protecting the geomembrane is required. In Korea, in accordance with the waste control act being modified in 1999, protecting the geosynthetics liner on top of the slope of landfill and installing a drainage layer to fluently drain leachate became mandatory, and technologies are being researched to both protect the geomembrane and quickly drain leachate simultaneously. Therefore, this research has its purpose in studying the drainage functions of leachate and protection functions of the geomembrane in order to examine the application possibilities of Geo-Multicell-Composite (GMC) as a Leachate Collection Removal and Protection System (LCRPs) at the slope on top of the geomembrane of landfill by observing methods of inserting filler with high-quality water permeability at the drainage net. GMC's horizontal permeability coefficient is $8.0{\times}10^{-4}m^2/s$ to legal standards satisfeid. Also crash gravel used as filler respected by vertical permeability is 5.0 cm/s, embroidering puncture strength 140.2 kgf. A result of storm drain using artificial rain in GMC model facility, maxinum flow rate of 1,120 L/hr even spray without surface runoff was about 92~97% penetration. Further study, instead of crash gravel used as a filler, such as using recycled aggregate utilization increases and the resulting construction cost is expected to savings.