• Journal of the Korean Recycled Construction Resources Institute
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• 제6권3호
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• pp.160-166
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• 2018

The purpose of this study is to investigate experimentally the effects of aspect ratio of polyethylene fiber on the compressive strength and tensile behavior of alkali-activated cementless composite. Two mixtures were determined according to aspect ratio values of polyethylene fibers, and the compressive strength and tension tests were performed. Test results showed that the effect of aspect ratio of fiber on the compressive strength was negligible and the tensile strength, ductility, and number of cracks of the mixture including the fiber with high aspect ratio were higher than those of the mixture including the fiber with low aspect ratio. On the other hand, the crack spacing and crack width were low in the mixture including the fiber with high aspect ratio.

• Korean Chemical Engineering Research
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• 제50권3호
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• pp.421-426
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• 2012

The effect of synthesis conditions such as various organic material and composition of organic-inorganic material in ozone resistance and surface characteristic of ultraviolet cured organic-inorganic hybrid coating film has been investigated. Organic-inorganic hybrid coating solution was prepared using tetraethoxysilane (TEOS), silane coupling agent methacryloyloxypropyltrimethoxysilane (MPTMS), 2,2,2-trifluoroethylmethacrylate, and various organic materials with acrylate group, bar-coated on substrates using applicator and densified by UV-curing. It was found that ozone resistance and surface hardness of the coating film was increased with contents of TEOS. It was also found that ozone resistance of coating film was increased with contents of 2,2,2-trifluoroethylmethacrylate. On the other hand, surface hardness was decreased with increase of 2,2,2-trifluoroethylmethacrylate. In addition, Surface hardness of coating film was increased with the addition of aliphatic urethane acrylate. It was also found that the transmittance of coating films was not influenced by content of TEOS and 2,2,2-trifluoroethylmethacrylate. In addition, the coating film exhibited high transmittance of above 90%.

• Earthquakes and Structures
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• 제14권6호
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• pp.615-626
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• 2018

The seismic vulnerability of Turkey is relatively high due to its active fault systems with potential to create destructive earthquakes. Thus, reducing the loss of life and property, the number of the earthquake-prone buildings and their retrofit requirements are considerably significant key issues under the scenario earthquakes. The street survey based rapid assessment (SSRA) method can be considered as a powerful tool to determine the seismic vulnerability of building stock of an earthquake-prone city/state. In this study, the seismic vulnerability of the building stock of the Kirikkale province in Turkey is aimed to be estimated adopting the street survey based rapid assessment method (SSRA). For this purpose, central 2074 existing reinforced concrete (R/C) buildings were structurally surveyed with rapid visual site screening and disadvantages such as, the existence of short-column, soft-story, heavy overhangs, pounding effect and local soil conditions were determined for obtaining the structural performance score of each. The results obtained from the study demonstrate that 11-25% of the surveyed buildings in the study region needs to be investigated through more advanced assessment methods. Besides, higher correlation between increasing story number and unsafe/safe building ratio is obtained for the buildings with soft-story parameter than that for those with heavy overhangs and short-column parameters. The conformity of the results of the current study with the previous documented cases of rapid assessment efforts in the recent earthquakes in Turkey shows that the SSRA method for the Kirikkale province performed well, and thus this methodology can be reliably used for similar settlement areas.

• Journal of the Korean Recycled Construction Resources Institute
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• 제8권2호
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• pp.204-211
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• 2020

Poly-Lactic Acid(PLA) fiber is an eco-friendly material and is biodegradable, so it can be utilized for manufacturing porous construction materia ls with interna l pore connection. In this study, domestic PLA fiber products(0.5mm india meter, 1.0mm in length, 10mm in length) were tested for melting at high temperatures and high alkality, and they were incorporated with FA-based geopolymer. Compressive strength was obtained through high temperature curing and alkali activator, however the complete melting of the PLA fiber was not ensured. The previous study handling PLA fiber with 0.003mm in diameter was completely dissolved, but 0.5mm and 1.0mm in diameter showed 42.5% and 33.3% of dissolution ratio, respectively. In addition, the increasing fiber volume led floating fibers during curing, which had a negative effect on its workability and solubility. Although the properties of PLA fiber may vary depending on the raw materials and production conditions, PLA fiber with 0.1mm or less diameter is recommended for porous construction material.

• Structural Engineering and Mechanics
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• 제69권1호
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• pp.11-20
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• 2019

The biaxial failure mechanism of transversally bedding concrete layers was numerically simulated using a sophisticated two-dimensional discrete element method (DEM) implemented in the particle flow code (PFC2D). This numerical modelling code was first calibrated by uniaxial compression and Brazilian testing results to ensure the conformity of the simulated numerical model's response. Secondly, 21 rectangular models with dimension of $54mm{\times}108mm$ were built. Each model contains two transversely bedding layers. The first bedding layer has low mechanical properties, less than mechanical properties of intact material, and second bedding layer has high mechanical properties, more than mechanical properties of intact material. The angle of first bedding layer, with weak mechanical properties, related to loading direction was $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$ while the angle of second layer, with high mechanical properties, related to loading direction was $90^{\circ}$, $105^{\circ}$, $120^{\circ}$, $135^{\circ}$, $150^{\circ}$, $160^{\circ}$ and $180^{\circ}$. Is to be note that the angle between bedding layer was $90^{\circ}$ in all bedding configurations. Also, three different pairs of the thickness were chosen in models, i.e., 5 mm/10 mm, 10 mm/10 mm and 20 mm/10 mm. The result shows that in all configurations, shear cracks develop between the weaker bedding layers. Shear cracks angel related to normal load change from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Numbers of shear cracks are constant by increasing the bedding thickness. It's to be noted that in some configuration, tensile cracks develop through the intact area of material model. There is not any failure in direction of bedding plane interface with higher strength.

• Computers and Concrete
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• 제27권3호
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• pp.241-252
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• 2021

An experimental program was conducted to investigate the fresh properties, mechanical properties and durability characteristics of the self-compacting mortars (SCM) produced with pumice powder and Artificial Lightweight Fine Aggregate (aLWFA). aLWFA was produced by using fly ash. A total of 16 different mixtures were designed with a constant water-binder ratio of 0.37, in which natural sands were partially replaced with aLWFA and pumice powder at different volume fractions of 5%, 10% and 15%. The artificial lightweight aggregates used in this study were manufactured through cold bonding pelletisation of 90% of class-F fly ash and 10% of Portland cement in a tilted pan with an ambient temperature and moisture content. Flowability tests were conducted on the fresh mortar mixtures beforehand, to determine the self-compacting characteristics on the basis of EFNARC. To determine the conformity of the fresh mortar characteristics with the standards, mini-slump and mini-V-funnel tests were carried out. Hardened state tests were conducted after 7, 28 and 56 days to determine the flexural strength and axial compressive strength respectively. Durability, sorptivity, permeability and density tests were conducted at the end of 28 days of curing time. The test results showed that the pumice powder replacement improved both the fresh state and the hardened state characteristics of the mortar and the optimum mixture ratio was determined as 15%, considering other studies in the literature. In the aLWFA mixtures used, the mechanical and durability characteristics of the modified compositions were very close to the control mixture. It is concluded in this study that mixtures with pumice powder replacement eliminated the negative effects of the aLWFA in the mortars and made a positive contribution.

• Computers and Concrete
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• 제29권 6호
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• pp.393-405
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• 2022

Lightweight concrete is a superior material due to its light weight and high strength. There however remain significant lacunae in engineering knowledge with regards to shear failure of lightweight fiber reinforced concrete beams. The main aim of the present study is to investigate the optimum usage of steel fibers in lightweight fiber reinforced concrete (LWFRC). Multi-scale finite element model calibrated with experimental results is developed to study the effect of steel fibers on the mechanical properties of LWFRC beams. To decrease the amount of steel fibers, it is preferred to reinforce only the middle section of the LWFRC beams, where the flexural stresses are higher. For numerical simulation, a multi-scale finite element model was developed. The cement matrix was modeled as homogeneous and uniform material and both steel fibers and lightweight coarse aggregates were randomly distributed within the matrix. Considering more realistic assumptions, the bonding between fibers and cement matrix was considered with the Cohesive Zone Model (CZM) and its parameters were determined using the model update method. Furthermore, conformity of Load-Crack Mouth Opening Displacement (CMOD) curves obtained from numerical modeling and experimental test results of notched beams under center-point loading tests were investigated. Validating the finite element model results with experimental tests, the effects of fibers' volume fraction, and the length of the reinforced middle section, on flexural and residual strengths of LWFRC, were studied. Results indicate that using steel fibers in a specified length of the concrete beam with high flexural stresses, and considerable savings can be achieved in using steel fibers. Reducing the length of the reinforced middle section from 50 to 30 cm in specimens containing 10 kg/m3 of steel fibers, resulting in a considerable decrease of the used steel fibers by four times, whereas only a 7% reduction in bearing capacity was observed. Therefore, determining an appropriate length of the reinforced middle section is an essential parameter in reducing fibers, usage leading to more affordable construction costs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제23권3호
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• pp.175-184
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• 2023

Korean Wave is now internationalized through the internet by social media, which have no space-time restrictions. This research examine the continuance use of K-Pop promotion using social media in Indonesia. In this study we apply the Expectation-Confirmation Model to analyze the effects of individual self-efficacy and perceived enjoyment on perceived usefulness, confirmation, and satisfaction of Social Media. As a research method for that purpose, the conformity of the model and the research hypothesis were verified using the structural equation model. As a result, it was found that the perceived enjoyment positively influences perceived usefulness, self-efficacy has a positive influence on perceived usefulness. We also found that confirmation positively affects both perceived usefulness and satisfaction, and that perceived usefulness positively affects satisfaction. Finally, satisfaction was found to always have a positive effect on intention to use.

• Journal of the Korean Recycled Construction Resources Institute
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• 제11권4호
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• pp.391-399
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• 2023

Recently, low-temperature pyrolysis technology has been studied as a recycling method for waste plastic. Low-temperature pyrolysis technology for waste plastic produces pyrolysis oil that can be used as an energy resource, but solid residue remains. Waste plastic pyrolysis residues are mostly landfilled due to their limited use. In this study, it is investigated that mixed waste plastic pyrolysis residues could be recycled into activated carbon. It was confirmed that the fixed carbon content of the residue was 33.69 % from proximate Analysis. Chemical activation was used to manufacture activated carbon. KOH was used as an activator. To investigate the effect of the mixing ratio of KOH and residue, samples were mixed at ratios of 0.5, 1.0, and 2.0. The mixed sample was chemically activated at an activation temperature of 800 ℃ for 1 hour. As a result of analyzing the characteristics of activated carbon through BET, it was confirmed that the specific surface area increased as the mixing ratio of KOH increased.

• The Journal of Dong Guk Oriental Medicine
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• 제4권
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• pp.25-52
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• 1995

'Sang Han Lon' became the sources for treatment and prescription in the Oriental medicine. After that, for some 1800 years the various writings for studying in many ways more than 1000 books which many old sages really intended to inquire into and study the value of books. It is considered that it is the result which the old sages tried to grope for many-sided directions in order to understand 'Sang Han Lon'. In this study, I tried to inquire into prescription and its relevant medicinal substances, that is to say, the crystalization of the physiology, pathology and treating method on the basis of the academic sources of his thoughts. The method to approach is "from what basis of thought system was 'Sang Han Lon' derived first of all?" Secondly, how was the thought system, which became the basis of 'Sang Han Lon', applied to concretely? I studied on the basis of the above important two problems. It is well known to everybody that 'Sang Han Lon' succeeded to the tradition of Naekyung(內經) as well as Cwuyek(周易, Chinese classic on divination). Besides, I inquired into and arrived at conclusion as follows that how the viewpoint on the balance(平衡觀), which was one of the common point between. Cwuyek(周易) and medical science in case of the 'Sanghan prescription'(傷寒方), was applied to concretely. 1. In naming, it is considered that from the same interconnection which the common point with Cwuyek(周易) was the same as obtaining the imigination(取象), the imagination was obtained and was named. 2. In case of being concerned in the gastro-intestinal track, namely, the core of the balance and harmony with the balance and harmony being emphasized, '理中'(It implies 'taking care of gasstro-intestinal track')" and '建中'(It implies 'establishing of gastro-intestinal track'), that is to say, '中'(It implies 'taking care of' & 'establishing of gastro-intestinal track') was emphasized much more. 3. In case of treatment taking advantage of three kinds of medicine in draught, powder and pills in the prescription, while treating during adjusting the slowness and fastness, I maintained the harmony not to damage the righteousness(正氣). 4. In case of the prescription, when exhaling(發散), astringing(收斂), loosing bowels, protecting the gastro-intestinal track and vomitting, he used the medicinal sustances in order to protect the gastro-intestinal track and treated not to damage the righteousness. 5. Especially, in case of the prescription in order to adjust the negative and positive principle of inside-outside(素囊陰陽), he composed of medicinal substances relevant to hot, cold, spicy and sour(寒熱辛酸) in conformity with the prescription and I paid much more attention to the one-sided treatment. Considering the various prescriptions, it is regarded that the adjusting prescription is kept its balance. 6. In the way of processing the medicinal substances in order to change effect of medicine in conformity with the reenactment, he tried to plan the balance of '一升一降' with the decrease of RHEI RADIX ET RHIZOMA(大黃) and increase of wine. 7. In boiling the medicine, he boiled the composed medicine in the time sequence for the purpose of adjusting the slowness and fastness and adapted to harmony of the negative and positive principle(陰陽調和) on the essence function(體峻用純). 8. In taking medicine, he tried to reduce the time of taking the medicine in case of being boiled slowly and tried to increase the dosage and eventually he planned the balance of one time slowness and one time fastness. As I inquired into the above result, a few steps for protecting method to boil the relevant medicinal substances, how to take the medicine and how to process the composed medicinal substances in order to change the effect of medicine can make the human body, which the disease penetrate into, go forward to the righteousness(正氣) and what is much beter, it is considered that this protecting method can be a carefully considerable one in order to protect the righteousness and can subdue the disease, not to damage the gastro-intestinal track and there can exist the viewpoint of balance(平衡觀) on its core.