• The Korean Journal of Elementary Counseling
• /
• 제9권1호
• /
• pp.95-110
• /
• 2010

The purpose of this research is to investigate how the Peer-Praise Activity program influence the Elementary School Students' Peer-Relationship and Class Cohesiveness. 2 Classes from the 5th grade of J elementary school in Seoul were selected as experimental group and control group. After the Peer-Praise Activity program was applied to experimental group, a post-test was given to verify the effects of the program. After one month, follow up-test was conducted to check the effect of durability on program. The program was applied to experimental group to check the inadequency and problem. Contrastively, control group had no application of the program. The results of this study are as follows : Compared to control group, experimental group that participated in the Peer-Praise Activity program showed significant improvement(p<.05) in Peer-Relationship and Class Cohesiveness. To supplement the results of quantitative analysis, opinion documents and qualitative analysis were executed. It shows that children had help of having confident school life by improving friendship and having a sense of unity and community spirit. In follow up-test result, it is known that the effect of Peer-Praise Activity Program is continued in Peer-Relationship and Class Cohesiveness and its all sub-factors except Communal life with friends which is one of the sub-factor in Peer-Relationship. The results above prove that Peer-Praise Activity Program has a positive effect on the Peer-Relationship and Class Cohesiveness for elementary school students. But it is needed to study long-term conducted program to improve durability effect. And curriculums and subjects which is able to connected with program should be studied continually.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제18권1호
• /
• pp.119-127
• /
• 2014

The application of sulfur polymer emulsion (SPE) as an acrylate substitute for semi-rigid pavement grout was evaluated, and the performance improvement by employing PVA fibers were also evaluated. The result indicated that the filling ratio of semi-rigid pavement material decreased as the fiber content increased, but it was measured to be 92~94% in every mixing condition, which satisfies the target performance, 90%. The maximum Marshall stability value of semi-rigid pavement material was measured to be 25.4 kN, which is about 4.7 times higher than the Korean Standard required for semi-rigid pavement material, 5.0 kN. The dynamic stability evaluation of semi-rigid pavement material indicated that the resistance to deformation from the wheel tracking test was improved by an SPE substitution, and in every mixing condition, the deformation converged to a constant value after 45 minutes with the same dynamic stability of 31,500 times/mm. The strain at the flexural failure was about 0.53%, which shows superior rigidity to asphalt pavements. The examination of abrasion resistance and impact resistance showed that the loss ratio was 9.8~6.0% in every mixing condition, which indicates a good abrasion resistance. Also, when fiber content ratio was 0.3%, the impact resistance was 2.82 times higher compared to plain (i.e., when fibers were not added). In the limited range of this study, an SPE substitution ratio of 30% was found to be an optimal level considering the mechanical and durability performance. In addition, it is thought that semi-rigid pavement material with superior performance could be manufactured if fiber content ratio up to 0.3% is applied depending on the purpose of use.

• The Journal of the Convergence on Culture Technology
• /
• 제6권2호
• /
• pp.535-541
• /
• 2020

A conventional elastic material replacement and performance evaluation are very complicated and time-consuming, and it is difficult to know when to replace the elastic material in advance. By comparing with the product limit and the functional limit, the necessity of elastic material replacement and the improvement of track support stiffness according to replacement can be immediately demonstrated based on experimental data. Using an evaluation system of track support stiffness, the performance evaluation data for elastic materials obtained through field tests using software for track support stiffness is integrated and managed on the administrator's computer. Therefore, the replacement plan is established and maintenance history is managed by identifying the replacement time and location of elastic materials. It is possible to evaluate the performance and condition of the elastic material at the various points during the working time of the track inspection and the track performance (track support stiffness) and durability of the elastic material (aging level, spring stiffness variation rate, etc.) at the operation condition. The elastic material could be replaced timely, and the deterioration of the elastic material can be continuously monitored.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제22권2호
• /
• pp.774-780
• /
• 2021

The auxiliary power unit (APU) of a rotorcraft starts the engine during operation/flying. The APU is composed of a gas turbine engine type. The starting principle of the component is that the electric start motor generates the power required for starting by rotating the shaft. In this study, quality improvement was performed by applying an over-running clutch (ORC) between the APU and the starter motor to secure the operability of the starter motor of the APU mounted on the rotorcraft. The starter motor has the main role of starting the APU, but during operation, it is rotated without load by the rotational force of the APU gear shaft, resulting in friction at the brush. This phenomenon causes abrasion of the brush of the starter motor. Consequently, when the APU operation time increases, the brush life decreases, and the operability of the APU is affected. In this study, an ORC that separates the interlocking between the start motor brush abrasion and the APU operation time was applied to improve the operability/durability of the APU starter motor. The effect was verified through a test, and the technical feasibility of the design change was analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제18권6호
• /
• pp.395-399
• /
• 2017

The LPI fuel filter housings used in automobiles were made from conventional die castings but have recently been developed by cold forging to improve the weight and durability. On the other hand, a sink may develop at the core of the forged product due to the resulting T-shape, which not only reduces the aesthetics, but also increases the post-processing cost of the product. Therefore, this research focused on methods to predict and mitigate sink development and progression during the T-shape forging process. Finite element analysis of the forging process was first performed to determine the optimal initial workpiece devoid of burrs and underfills. An accurate sink prediction was then obtained via metal flow analysis, which was a result of the finite element simulation. Through finite element analysis, it was confirmed that sink development is a product of the differences in nodal velocities arising from the T-shaped forging process. Consequently, a pad was inserted beneath the sink to minimize these velocity differences. The results yielded significant improvement with regard to the sink defect. This method was practically applied to an industrial site to validate the sink improvement.

• Journal of the Korean Recycled Construction Resources Institute
• /
• 제1권1호
• /
• pp.89-97
• /
• 2005

Recently, for the problem solution of demand and supply imbalance of fine aggregate due to the shortage of natural fine aggregate resource and the environment regulation on sea sand extraction in the construction field, the studies for the application of recycled fine aggregate using waste concrete are being progressed versatilely. On the other hand, the treatment of fly-ashes that of industrial by-product originated in the steam power plant is discussed by the continuous increasing of origination quantities. In the ease of using fly-ash, advantages are the improvement of workability, viscosity and long-time strength, and the reduction of hydration heat under the early ages, as the admixtures for concrete, but the studies for the application of fly-ash as recycled concrete admixtures are inadequacy. There fore, in this study, through investigating the properties of fresh, hardened and durability according to the replacement of recycled fine aggregate and fly-ash, it is intended to propose the fundamental data for structural application of recycled concrete using recycled fine aggregate and fly-ash. As the result of this study, they arc shown that the engineering properties and durability, in the case of replacement ratio 100% of recycled fine aggregate, arc similar to those of concrete using natural fine aggregate, so it is considered that recycled fine aggregate could be used as the fine aggregate for concrete. Also, the performances of recycled concrete are improved by replacing fly-ash.

• Geomechanics and Engineering
• /
• 제36권1호
• /
• pp.39-50
• /
• 2024

Bitumen and high-quality subangular aggregates, the two principal materials used for asphalt concrete construction, are finite and expensive materials. The general availability of crumb rubber and naturally occurring aggregates of different shapes, especially flat and elongated shapes, indicates that they are feasible alternative materials for expanding the volume of bitumen and utilizing a wider range of aggregate shapes for the development of asphalt concrete, with an associated environmental benefit. The study investigated the effect of adding up to 15% crumb rubber and aggregates sorted into different groups, i.e., rounded, elongated, flat, and their combinations, on the rheological and mechanical properties and durability of 50/70 of hot-mix asphalt pavement. The addition of crumb rubber decreased ductility and penetration but increased the softening point. For a 5.5% bitumen content, asphalt concrete briquettes consisting of 7% crumb rubber and three types of aggregate shapes, i.e., 100% rounded, a mix of 75% rounded and 25% elongated, and a mix of 75% rounded, 15% elongated and 10% flat, were associated with high Marshall stability and indirect tensile strength as well as low lateral deformation due to their high solidity and moderate angularity ratio. Also, the addition of 7% crumb rubber resulted in a significant improvement in the tensile strength ratio and rebound strain of briquettes consisting of 75% rounded and 25% elongated aggregates and those with 75% rounded, 15% elongated and 10% flat aggregates. In relation to the parameters investigated, the three groups of briquettes met some of the local (South Africa) requirements for the surface course and base course of low traffic volume roads.

• Journal of the Korean Society of Safety
• /
• 제33권4호
• /
• pp.90-97
• /
• 2018

As the result(also after it's been carried out the damping force test with 800ea lateral dampers of 50ea trainset from entering heavy maintenance workshop to implement heavy maintenance inspection cycle, there were 86.25%(650ea) which were out of $350kg{\pm}15%$ of the standard value of damping force compared to the reference value. After the implementation of heavy maintenance inspection cycle, it's been examined damping force test with total samples 32ea(samples 8ea per a trainset) from actual running EMU 4ea trainset. As the result, percent defective was 84.4%(27ea), which was a very high level. System. The lateral damper's the failure cause of damping force defective was oil leakage caused by tearing crack of oil seal and foreign material in oil iron 473 ~ 1932 times higher than that of new oil, copper 36 ~ 98 times higher than that of new oil reduced oil amount cycling damping valve. It resulted from the change cause of damping force. In the static analysis on the shape of lateral damper oil seal's the existing and improved product, the stress of the improved product was smaller than that of the existing product. In the fatigue analysis, the existing product showed a low life in the upper area. However, in case of the improved product, it could be confirmed that the destruction did not occur up to the specified 1.0e + 006 cycles and the lifetime was further improved in most areas.

• Fashion & Textile Research Journal
• /
• 제21권5호
• /
• pp.640-655
• /
• 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.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 한국표면공학회 2007년도 추계학술대회 논문집
• /
• pp.61-62
• /
• 2007

HVOF thermal spray coating of micron size Co-alloy powder has been studied for the durability improvement of high velocity spindle (HVS). Optimal coating process of this system for the best surface properties is hydrogen flow rate 75 FMR, oxygen flow rate 38-42 FMR, feed rate 30 g/min at spray distance 5 inch. Friction coefficient (FC) and wear trace (WT) decrease increasing coating surface temperature from 25$^{\circ}$C to 538$^{\circ}$C due to the higher lubricant effects of the oxides at the higher temperature. At the study of adhesion of T800 coating on a light metal alloy Ti-6Al-4V (Ti64) tensile bond strength (TBS) and tensile fracture location (TFL) of Ti64/T800 are 8,740 psi and near middle of T800 coating respectively. This shows that adhesion of Ti64/T800 is higher than the cohesion strength (8,740 psi) of T800 coating. Therefore T800 coating is strongly advisable for the surface coating on HVS such as high speed air-bearing spindle.