• Korean Journal of Materials Research
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• v.27 no.12
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• pp.652-657
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• 2017

The use of continuous welded rail is increasing because of its many advantages, including vibration reduction, enhanced driving stability, and maintenance cost savings. In this work, two different types of continuous welded rails were examined to determine the influence of repeated wheel-rail contact on the crystal structure, microstructure and mechanical properties of the rails. The crystal structure was determined by x-ray diffraction, and the microstructure was examined using optical microscopy and scanning electron microscopy. Tensile and microhardness tests were conducted to examine the mechanical behaviors of prepared specimens taken from different positions in the cross section of both newly manufactured rail and worn rail. Analysis revealed that both the new and worn rail had a mixed microstructure consisting of ferrite and pearlite. The specimens from the top position of each rail exhibited decreased lamella spacing of the pearlite and increased yield strength, ultimate tensile strength and hardness, as compared with those from other positions of the rail. It is thought that the enhanced mechanical property on the top position of the worn rail might be explained by a mixed effect resulting from a directional microstructure, the decreased lamella spacing of pearlite, and work hardening by the repeated wheel-rail contact stress.

• Journal of the Korea Convergence Society
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• v.10 no.11
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• pp.297-302
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• 2019

A-pillar is closely related to safety for the purpose of protecting the bodies of passengers by mitigating the impact that may be caused by the vehicle being overturned while driving. Therefore, the A-pillar should protect these parts from a variety of dynamic loads. This study result is thought to contribute for the strength and durability of A-pillar by designing two types of parts before making this product and analyzing the product which thickness is adjusted for the light weight of vehicle. If this study result is practically applied to the parts of A-pillar in a car, it is considered that the damage can be protected by the durability verification of design. By utilizing the data of analysis and design on the strength and durability of automotive A-pillar in this study, the esthetic sense can be given by being grafted onto the real automotive part.

• Journal of IKEEE
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• v.25 no.3
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• pp.578-583
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• 2021

This paper describes acceleration tests for reliability of semiconductors. It also describes AEC-Q100, international test standard for reliability of automotive semiconductors. Semiconductors can be used for dozens of years. So acceleration tests are essential to test potential problems over whole period of product where test time is minimized by applying intensive stresses. AEC-Q100 is a typical acceleration test in automotive semiconductors, and it is designed to find various failures in semiconductors and to analyze their causes of occurance. So it finds many problems in design and fabrication as well as it predicts lifetime and reliability of semiconductors. AEC-Q100 consists of 7 test groups such as accelerated environmental stress tests, accelerated lifetime simulation tests, package assembly integrity tests, die fabrication reliability tests, electrical verification tests, defect screening tests, and cavity package integrity tests. It has 4 grades from grade 0 to grade 3 based on operational temperature. AEC-Q101, Q102, Q103, Q104, and Q200 are applied to discrete semiconductors, optoelectronic semiconductors, sensors, multichip modules, and passive components, respectively.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.165-170
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• 2019

This study carried out the structural analysis and vibration analysis on scooter seat. By comparing with three kinds of B-bone A, Julio B, and City Ace C, the load was applied to scooter seat as much as a weight of person. Through structural analysis, this study examined which seat is most deformed by comparing the deformation each other or affords passengers most convenience and does not afford passengers the inconvenience by absorbing the vibration during driving. Model C has the most total deformation at the structural analysis result and Model B is seen to be changed to be convenient to sit the deformation as it deforms largely. Through this study, which seat is most convenient and becomes strong on durability can be confirmed. As the durability analysis result data of scooter seat model obtained on the basis of this study result are utilized, the esthetic sense can be shown by being grafted onto the machine or structure at real life.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.290-296
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• 2019

Head-up displays for vehicles play an important role in displaying various information about the safety and convenience of driving on the windshield of the vehicle. In this study, ultra-precision machining was performed and evaluated as a method for machining a large-area aspheric free-form mirror that is applicable to augmented reality technology. Precision diamond cutting is highly accurate and suitable for the production of advanced parts with excellent surface integrity, low surface roughness, and low residual stress. By using an aspheric free-form mold, it is possible to improve the optical transfer function, reduce the distortion path, and realize a special image field curvature. To make such a mold, the diamond cutting method was used, and the result was evaluated using an aspherical shape-measuring machine. As a result, it was possible to the mold with shape accuracy (PV) below $1{\mu}m$ and surface roughness (Ra) below $0.02{\mu}m$.

• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.39-46
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• 2019

The liquefaction is a phenomenon that the effective stress becomes zero due to the rapidly accumulated excess pore water pressure when a strong load acts on the ground for a short period of time, such as an earthquake or pile driving, resulting in the loss of the shear strength of the ground. Since the Geongju and Pohang earthquake, liquefaction brought increasing domestic attention. This liquefaction can be assessed mainly through the semi-empirical procedures proposed by Seed and Idriss (1982) and the liquefaction risk based on the penetration resistance obtained from borehole DB and SPT. However, the geotechnical information data obtained by the in-situ tests or boring information fundamentally have an issue of the representative of the target area. Therefore, this study sought to construct a ground information database by classifying and reviewing the ground information required for liquefaction assessment, and tried to solve the representative problem of the soil layer that is subject to liquefaction evaluation by performing spatial interpolation using GIS.

• Journal of Drive and Control
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• v.17 no.4
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• pp.141-151
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• 2020

The aim of this study was to analyze the safety factor of range-shift gear pairs on multi-purpose agricultural implement machinery for an optimal design of a transmission system. Gear-strengths such as bending and contact stress and safety factors were analyzed under three load conditions: an equivalent engine torque at plow tillage, a rated engine torque, and the maximum engine torque. Root and contact safety factor were calculated to be 3.88, 5.14, 2.24, 2.11, 2.21, 0.99 and 0.78, 0.94, 0.65, 0.68, 0.84, 0.85, respectively, under equivalent engine torque condition at the plow tillage. The root and contact safety factor were calculated to be 1.91, 2.53, 1.10, 1.04, 1.07, 0.48 and 0.55, 0.66, 0.46, 0.48, 0.59, 0.59, respectively, under rated engine torque condition. The root and contact safety factor were calculated to be 1.60, 2.11, 0.92, 0.87, 0.90, 0.40 and 0.51, 0.61, 0.42, 0.44, 0.54, 0.54, respectively, under the maximum engine torque condition. The multi-purpose agricultural implement machinery could be conducted under plow tillage operation. However, gear specifications for tooth surface need modification because the gear surface would be broken at all driving conditions as safety factors are lower than 1.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.1-16
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• 2022

This work elaborately investigates the influences of the guideway geometry parameters and track irregularity on the dynamic performances of the suspended monorail vehicle-guideway system (SMVGS). Firstly, a spatial dynamic analysis model of the SMVGS is established by adopting ANSYS parameter design language. Then, the dynamic interaction between a vehicle with maximum design load and guideway is investigated by numerical simulation and field tests, revealing the vehicle-guideway dynamic features. Subsequently, the influences of the guideway geometry parameters and track irregularity on the dynamic performances of the SMVGS are analyzed and discussed in detail, and the reasonable ranges of several key geometry parameters of the guideway are also obtained. Results show that the vehicle-guideway dynamic responses change nonlinearly with an increase of the guideway span, and especially the guideway dynamic performances can be effectively improved by reducing the guideway span; based on a comprehensive consideration of all performance indices of the SMVGS, the deflection-span ratio of the suspended monorail guideway is finally recommended to be 1/1054~1/868. The train load could cause a large bending deformation of the pier, which would intensify the car-body lateral displacement and decrease the vehicle riding comfort; to well limit the bending deformation of the pier, its cross-section dimension is suggested to be more than 0.8 m×0.8 m. The addition of the track irregularity amplitude has small influences on the displacements and stress of the guideway; however, it would significantly increase the vehicle-guideway vibrations and rate of load reduction of the driving tyre.

• Korean Journal of Culture and Social Issue
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• v.22 no.2
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• pp.285-311
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• 2016

This study analysed the published papers dealing with traffic behaviors since 2004 in south Korea. The following information was coded for each papers; year of publication, source, authors, main topic, and subtopic. The annual numbers of publication in 2004 and 2005 showed 6 articles and 7 articles. Since 2006, The annual numbers were increasing more than 10 papers. It means that the researches on traffic behavior were rich. The driver was main topic of 73.2% of articles. Cognition & Perception, Fatigue and Stress, and Alcohol were the main interest sub-topics dealing with main topic driver. Elderly driver was 10.4%, the interest in elderly drivers grew with population aging. And the dominant publications were Journal of traffic safety research, Journal of Korean Psychology Association, and Journal of the Koean Data Analysis Society with 60% of all articles for last 10 years.

• Journal of Animal Science and Technology
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• v.66 no.2
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• pp.279-294
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• 2024

Agriculture has played a significant role in the national economy, contributing to food security, driving economic growth, and safeguarding the dietary habits of the population. Korean agriculture has been compelled to focus on intensive farming due to its limited cultivation area, excessive input costs, and the limitations of agricultural mechanization. In the Republic of Korea (R.O.K), the concept of environmentally friendly animal agriculture began to be introduced in the early 2000s. This concept ultimately aims to cultivate sustainable animal agriculture (SAA) through environmentally friendly production practices, ensuring the healthy rearing of animals to supply safe animal products. Despite the government's efforts, there are still significant challenges in implementing environmentally friendly agriculture and SAA in the R.O.K. Therefore, the objective of this review is to establish the direction that the animal agriculture sector should take in the era of climate crisis, and to develop effective strategies for SAA tailored to the current situation in the R.O.K by examining the trends in SAA in the U.S. The animal agriculture sector in the U.S. has been working towards creating a SAA system where humans, animals, and the environment can coexist through government initiatives, industry research, technological support, and individual efforts. Efforts have been made to reduce emissions like carbon, and improve factors affecting the environment such as the carbon footprint, odor, and greenhouse gases associated with animal agriculture processes for animals such as cattle and pigs. The transition of the U.S. towards SAA appears to be driven by both external goals related to addressing climate change and the primary objectives of responding to the demand for safe animal products, expanding consumption, and securing competitiveness in overseas export markets. The demand for animal welfare, organic animal products, and processed goods has been increasing in the U.S. consumer market. A major factor in the transformation of the U.S. animal agriculture sector in terms of livestock specifications is attributed to environmentally friendly practices such as high-quality feed, heat stress reduction, improvements in reproductive ability and growth period reduction, and efforts in animal genetic enhancement.