• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.44-53
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• 2021

As environmental issues have emerged worldwide, emission gas regulations have been strengthened. In the construction machinery sector, studies have been actively conducted to utilize the power source of electric motors owing to the increasing demand for zero emissions. In this study, the gear specifications of an electric axle for construction machinery were selected by considering the specifications of the motor, gear tooth contact pattern, and face load factor. The gear strength evaluation was performed at the system level using the simulation model. The bending and contact strength of the spiral bevel gears and the bending strength of the planetary gear set showed a safety factor of 1 or more. However, the contact strength of the planetary gear set showed a safety factor of 0.92. Conservative results were derived by performing the analysis under the rated load condition of the motor. However, the ratio of the equivalent torque to the rated torque of the motor was 45% or less, hence, it was determined that no difficulties should arise regarding the durability of the axle.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.650-657
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• 2021

Alkali activators that stimulate mineral compounds are expensive materials, but in order to replace industrial products of high alkali in gredien ts, both product an d econ omic feasibility must be satisfied. In this study, alkali in dustrial waste(LW) from the LCD man ufacturin g process were used for the purpose of alkali active reaction of GGBFS for high stren gth concrete over 50MPa. Concrete mixed with LW had reduced workability, but it had the characteristic of increasing compressive strength. Analysis using ACI 209 Compressive Strength Model Equation was made to compare the changes in strength coefficients according to LW mixing. The durability test of concrete, such as Chloride Penetration Resistance and carbonation resistance, also showed excellent performance. In the Adiabatic temperature rise test results, the concrete mixed with LW had the effect of accelerating the initial hydration heat. However, the final Adiabatic temperature rise was not significantly affected by the mixing of LW.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.469-477
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• 2021

In this study, the mechanical property of anti-fouling coating using CNF was evaluated to prevent the durability and stability of structure exposed the marine environment. Anti-fouling coating using CNF was prepared by CNF, AKD and waste glass powder, and contact angle test, drying time, viscosity analysis and microstructure were performed. When coating on one number of times, It was showed to relatively high hydrophobic performance in steel. And It was confirmed that the contact angle increased as the content of AKD increased in cement mortar. When coating on three number of times, the surface was confirmed super-hydrophobic at maximum of 151.6°. When mixing waste glass powder, the surface was showed to relatively high hydrophobic. It is pseudo plastic fluid when CNF and distilled water were prepared in a ratio of 1:1, And Anti fouling coating is judged to be suitable for use as coating on marine structure.

• Smart Structures and Systems
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• v.22 no.6
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• pp.727-741
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• 2018

To mitigate vibrations, tuned mass dampers(TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.287-297
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• 2019

Monitoring for the physiological state of a solider is essential to the realization of individual combat system. Despite all efforts over the last decades, there is no report to point out the optimal location of the wearable biosensors considering both monitoring accuracy and operational robustness. In response, we quantitatively measure body temperature and heartrate from 34 body parts using 2 kinds of biosensor arrays, each of which consists of a thermocouple(TC) sensor and either a photoplethysmography(PPG) sensor or an electrocardiography(ECG) sensor. The optimal location is determined by scoring each body part in terms of signal intensity, convenience in use, placement durability, and activity impedance. The measurement leads to finding the optimal location of wearable biosensor arrays. Thumb and chest are identified as best body parts for TC/PPG sensors and TC/ECG sensors, respectively. The findings will contribute to the successful development of individual combat system.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.131-137
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• 2019

The purpose of this study is to investigate the perception of buildings suspended from construction and to analyze the problems that are inherent and effective in the management of public officials and residents in the area where construction is suspended. There are 63 buildings in the Gangwon area, 16% of which are occupied by the whole area. 31% of the apartment houses are occupied the most, and 10 years or more is suspended. 241 of them accounted for 62%. In order to efficiently manage buildings that are suspended from construction, protection measures should be taken to ensure safety and prevent crime through periodic and continuous management of facility grade management that conforms to the special act on safety and maintenance of facilities. Effective support for budget and personnel is required for efficient management of construction suspended.

• Advances in concrete construction
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• v.8 no.1
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• pp.21-31
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• 2019

The rich recipe of ultra high performance concrete (UHPC) offers the higher mechanical, durability and dense microstructure property. The variable like cement/sand ratio, amount of supplementary cementitious material, water/binder ratio, amount of fiber etc. alters the UHPC hardened properties to any extent. Therefore, to understand the effects of these variables on the performance of UHPC, inevitably a stage-wise development is required. In the present experimental study, the effect of sand/cement ratio, the addition of finer material (fly ash and quartz powder) and, hybrid fiber on the fresh, compressive and microstructural property of UHPC is evaluated. The experiment is conducted in three phases; the first phase evaluates the flow value and strength attainment of ingredients, the second phase evaluates the efficiency of finer materials (fly ash and quartz powder) to develop the UHPC and the third phase evaluate the effect of hybrid fiber on the flow value and strength of ultra high performance hybrid fiber reinforced concrete (UHP-HFRC). It has been seen that the addition of fly ash improves the flow value and compressive strength of UHPC as compared to quartz powder. Further, the usage of hybrid fiber in fly ash contained matrix decreases the flow value and improves the strength of the UHP-HFRC matrix. The dense interface between matrix and fiber and, a higher amount of calcium silicate hydrate (CSH) in fly ash contained UHP-HFRC is revealed by SEM and XRD respectively. The dense interface (bond between the fiber and the UHPC matrix) and the higher CSH formation are the reason for the improvement in the compressive strength of fly ash based UHP-HFRC. The differential thermal analysis (DTA/TGA) shows the similar type of mass loss pattern, however, the amount of mass loss differs in fly ash and quartz powder contained UHP-HFRC.

• Fashion & Textile Research Journal
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• v.21 no.5
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• pp.640-655
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• 2019

Technology status was investigated by analyzing patents and development cases of wearable robots. Development direction of wearable robot for wearability was also suggested by understanding the problems of wearability from development cases through the FGI technique. The number of patents per technical field was the most in the field of strength support, but AI in the technology field was different in each country; Korea was found to be poor in the category of daily living assistance. The number of patents by technology category was the most in the category of muscular strength assistance. However, the values of AI in the technology category were different in each country; Korea was found to be poor in the category of daily living assistance. Development cases were focused on rehabilitation, so development is not fulfilled uniformly by use purpose. By wearing body parts, robots with single function type were mainly developed. Rigid material robots were mainly developed. It was confirmed that wearable robot technology is not developed evenly in the category of application because it is in the early stage of the technical proposal and centered on main performance improvement. We derived twelve wearable conditions for wearable robots: Shape and Size Appropriateness, Movement Appropriateness, Composition Appropriateness, Physiological Appropriateness, Performance Satisfaction, Ease of Operation, Safety, Durability, Ease of Dressing, Ease of Cleaning, Portability and Ease of Storage and Appearance Satisfaction. Finally, the development direction of a wearable robot for each wearable condition was suggested.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.394-399
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• 2019

Plywood is a laminated wood material where alternating layers are perpendicular to each other. It is used in a liquefied natural gas (LNG) carrier for an insulation system because it has excellent durability, a light weight, and high stiffness. An LNG cargo containment system (LNG CCS) is subjected to loads from gravity, sloshing impact, hydrostatic pressure, and thermal expansion. Shear forces are applied to an LNG CCS locally by these loads. For these reasons, the materials in an LNG CCS must have good mechanical performance. This study evaluated the shear behavior of plywood. This evaluation was conducted from room temperature ($25^{\circ}C$) to cryogenic temperature ($-163^{\circ}C$), which is the actual operating environment of an LNG storage tank. Based on the plywood used in an LNG storage tank, a shear test was conducted on specimens with thicknesses of 9 mm and 12 mm. Analyses were performed on how the temperature and thickness of the plywood affected the shear strength. Regardless of the thickness, the strength increased as the temperature decreased. The 9 mm thick plywood had greater strength than the 12 mm thick specimen, and this tendency became clearer as the temperature decreased.

• Journal of the Korean Society of Safety
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• v.34 no.2
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• pp.40-47
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• 2019

The Half-depth precast deck is a structural system that utilizes pre-cast panels pre-built at the factory as formwork at the construction stage and as a major structural member at the same time after completion. These systems have joints between segments, and the detail and performance of the joints are factors that have a very large impact on the quality, such as the constructability and durability of the bridge decks. In this study, strength performance evaluation was performed for improved joints using connecting rebar by experimental method. Static loading tests were conducted on the test specimen with improved joint, those with existing joint and those without joint. The test results of the specimens were compared to each other, and the flexural strength required by the design was compared. The flexural strength required in the design was presented by finite element analysis. It has been shown that the flexural strength of the specimens with joints were more than twice that required by the design. But the flexural strength of the specimen with existing joint was about 84% of that without joint. The flexural strength of the specimen with improved joints was a nearly similar degree of that compared to the specimen without joint. And a comparison of the moment-deflection relationship curves of the two specimens also shows a very similar flexural behavior. It is confirmed that improved joint has sufficient flexural strength. In addition to strength, the bridge decks require serviceability, such as deflection and cracking, and in particular, fatigue resistance due to repetitive live loads is an important performance factor. Therefore, further verification studies are required.