• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.132-132
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• 2016

기계 가공품의 정밀화, 경량화 요구로 난색재로 분류되는 비철분야 및 복합재 가공용 공구개발에 대한 수요가 급증하고 있으나, 기존 난삭재 가공 시 절삭공구의 마모가 빠르고, 상대재의 융착 불량 등이 공구 수명 감소의 주요 영향으로 보고된다. 상기문제를 해결하기 위해 절삭가공 공정 중 과다한 절삭유의 사용에 따른 가공비용, 에너지소모 증가, 환경오염 등으로 절삭유의 최소화 또는 절삭유를 사용하지 않는 표면처리기술등의 친환경 가공기술의 개발이 필요하다. 내융착 및 내마모 특성 향상을 위한 표면코팅 방법으로 수소가 포함되지 않은 고경도 비정질 카본 (ta-C)이 있으나, ta-C 코팅 막은 경도 30 - 80 GPa, 잔류응력 3 - 10 GPa 범위로 일반 경질 코팅 막 (AlTiN, TiSiCrN : 평균 3 GPa)에 비해 높고 산업적 활용이 가능한 0.5 - 1.5 um 두께 수준의 후막화가 힘들어 매우 우수한 절삭공구용 코팅 막 특성에도 불구하고 적용사례가 매우 적다. 따라서, 본 연구에서는 아크플라즈마 방식 (Filtered Cathode Vacuum Arc Plasma, FCVA)을 활용한 고경도/무수소 카본 코팅 막을 후막형태로 증착하여 비철금속가공용 절삭 공구류의 수명향상 기법을 제시하고자 한다. ta-C 코팅 막의 기초 공정개발 단계에서는 바이어스 전압, 공정시간을 달리하여 ta-C 코팅 막의 기계적 물성(경도: $50{\pm}3GPa$, 잔류응력: $6{\pm}1GPa$, 밀착력: 30N 이상 및 트라이볼로지 특성: 마찰계수 0.1 이하, 마멸량: $1.85{\times}10-14mm^3$)을 확보하여 절삭공구로의 공정실용화 적용검토를 실시하였다. ta-C 코팅 막은 (1) WC 공구 및 기존 상용품인 (2) TiAlN/TiN/WC 구조에 대해 증착을 실시하였으며 코팅 막의 두께 변화에 따른 실제 절삭환경에서의 내수명 관측을 진행하였다. 시험결과, ta-C/WC의 단일막 구조인 절삭공구의 경우, 실제 절삭환경에서 쉽게 박리가 발생하여 코팅 막으로서의 효과를 나타내지 못하였다. 이는, 기초 공정개발 단계에서의 밀착력 기준이 실제 환경과 부합하지 않는 것을 의미하며 추후 공정개선을 통해 극복하고자 한다. 반면에, 상용품인 (2) TiAlN/TiN/WC 구조의 절삭공구 대비 ta-C/TiAlN/TiN/WC 구조에서 내수명 증가는 약 2.5배 (기존 300회, 코팅 후 800회)로 증가하였으며 ta-C 코팅 막의 두께가 $0.6-0.8{\mu}m$일 때 최대치를 취한 후 감소하였다. 이를 통해, 절삭공구로의 ta-C 코팅 막 효과는 최외각 층의 두께 범위와 모재 강도보강을 할 수 있는 적절한 중간층 막 (TiN/TiAlN 층)이 혼합되어 나타난 것으로 사료되며 현재 산업계로의 적용을 위한 대량생산용 코팅장비의 개발 및 비용절감을 위한 공정개발이 진행 중이다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.449-458
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• 2023

As an adsorption technology for dissolved organic matter, the adsorption capacity of granular activated carbon, GAC, can be applied, but activated carbon whose adsorption capacity is significantly reduced by use is inevitably replaced or regenerated. However, due to the economics of replacement cost, thermal regeneration method is used commercially, but high energy cost and loss of activated carbon occur under high temperature conditions above 800℃. In this study, the Sono-Fenton method, a multi-oxidation technology that combines Fenton oxidation and ultrasonic oxidation, was applied to improve the regeneration efficiency of spent GAC used to treat dissolved organic matter in combined sewer overflows (CSOs), and the regeneration efficiency of spent GAC by oxidant and ultrasonic frequency was investigated. In the applied Sono-Fenton treatment, the highest regeneration efficiency of 68.5% was obtained under the regeneration conditions of Fe²⁺ 10 mmol/L, H₂O₂ concentration 1,000 mmol/L, ultrasonic treatment time of 120 min, and ultrasonic frequency of 40 kHz. And similar efficiency was also obtained at 750 kHz, while ultrasonic waves of other frequencies had poor regeneration efficiency, and the magnitude of frequency and GAC regeneration efficiency did not show a linear relationship. In the case of continuous operation of the GAC adsorption tower with CSOs prepared by diluting raw sewage, about 700 hours of operation without regeneration was possible, and as a result of applying one Sono-Fenton treatment, 40-70% COD_cr removal efficiency was obtained during a total of 1,000 hours of GAC adsorption operation.

• Journal of Biosystems Engineering
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• v.6 no.2
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• pp.65-76
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• 1982

This survey was conducted to investigate the status of repair and maintenance of 4 wheel tractor for a basic reference to the improvement of quality and proper utilization of tractors. Thirty two counties from eight provinces, except Jeju, were covered in this study in order to investigate annual break-down and repair of tractor in 1980. The analyzed results are summarized as follows; 1. The average number of break-down of large size tractors(47ps) was 5.0 times in a year and it was about twice of that of small size tractors(19-23ps). The break-down frequency per 100 hours of use was 1.11 times in the large size and 0.65 times in the small size tractors. 2. 75.6 percent of total break-down was occured in main body of tractor and 24.4 percent in attachments. In particular, the break-down of plow and rotavator was more than 80 percent of total break-down of the small size tractor attachments. 3. The large size tractors which were occured more than one times of break-down a year was 75 percent and its rate of the small size tractor was 62 percent. But 9 percent of tractor surveyed had more than ten times of break-down in a year 4. The frequency of break-down had a peak in May, and it was directly proportional to the hours of use. 5. The causes of break-down were poor maintenance and operation by 29.8 precent, old parts by 30.2 percent, poor quality of parts by 20.6 percent, poor field condition by 16.3 percent and others by 3.1 percent. 6. Annual number of repair was 5.5 times and among them 55.6 percent was done by shop and 44.4 percent by operator. 7. Total required repair time was 30.6 hours a year in the large size tractor and 19.9 hours in the small size tractor. Average repair time was 3.62 hours a time. 8. Annual repair cost was 278 thousand won in the large size tractor and 70 thousand won in the small size tractor. The repair cost per hour of use was 621 won in the large size and 198 won in the small size tractor. 9. The repair cost rate of tractor(Y) was regulated with tractor age (X) as follow; Y=0.752X In case of the service life of tractor was 10 years, the total repair cost rate was 64 percent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.603-608
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• 2018

Although the voltage-applied discharge method is most widely used in the semiconductor and display industries, periodic management costs are incurred because the method causes defects due to the absorption of ambient fine dust and causes emitter tip contamination due to the discharge. The emitter tip contamination problem is caused by the accumulation of fine particles in ambient air due to the corona discharge of the ionizer. Fuzzy ball generation accelerates the wear of the emitter tip and deteriorates the performance of the ionizer. Although a mechanical cleaning method using a manual brush or an automatic brush is effective for contaminant removal, it requires management of additional mechanical parts by the user. In some cases, contaminants accumulated in the emitter may be transferred to the wafer or product. In order to solve this problem, we developed an ionizer for a clean environment that can remove the pencil-type emitter tip and directly ionize the surrounding gas molecules using the tungsten wire located inside the ion tank. As a result of testing and certification by the Korea Institute of Machinery and Materials, the average concentration was $0.7572particles/ft^3$, the decay time was less than two seconds, and the ion valance was 7.6 V, which is satisfactory.

• Computational Structural Engineering
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• v.2 no.1
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• pp.65-70
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• 1989

An analytical study was conducted using the Galerkin technique to determine behaviour of thin fibrereinforced and laminated composite pipes under soil pressure. Geometric nonlinearity and material linearity have been assumed. It is assumed that vertical and lateral soil pressure are proportional to the depth and lateral displacement of the pipe respectively. It is also assumed that radial shear stress is negligible because the ratio of thickness to the radius of pipe is very small. The above results are verified by the finite element analysis.

• Journal of Korean Society of Disaster and Security
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• v.6 no.1
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• pp.79-86
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• 2013

As car-oriented road policies have been made forward so far, relatively pedestrians' walking conditions are so in poor environments that more than two thousand pedestrians die from car accidents every year. Pedestrians' walking right has been severely invaded like that. Pedestrians' walking right is a right that people are able to walk safely and comfortably in pleasant surroundings as long as they don't threaten the public safety, order maintenance, and welfare. The government has an obligation to provide safe, comfortable, and pleasant environments to pedestrians. Recently interests in pedestrians' safety are increasing, government-driven supports have been made to make safe, pleasant, and healthy walking surroundings. As poor walking condition improvement projects cost high, they should be progressed to accomplish maximal effects using finite finances efficiently, and post feasibility evaluations of the projects should be severely estimated. However site selecting indicators which satisfy with the goal for composing safe working surroundings have not been decided yet, though currently it has a legal basis to specify walking condition improvement sites by the Law for Pedestrians' safety and Comfort Increasement. Therefore this study focuses on suggesting improved ways for selecting sites where pedestrians' safe environment project by reviewing previous research. When project sites are selected, evaluation indicators related to awareness survey of residents and history should be excluded, and disaster safety assessments for walking safety facilities, latent human hazards and natural disasters like a strong wind are proposed besides evaluations on pedestrians' safety and walking environment for matching with the purpose of the project to make safe working surroundings.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.257-270
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• 2022

In this paper, we design a smart factory risk improvement system and risk improvement method using AI edge devices. The smart factory risk improvement system collects, analyzes, prevents, and promptly responds to the worker's work performance process in the smart factory using AI edge devices, and can reduce the risk that may occur during work with improving the defect rate when workers perfom jobs. In particular, based on worker image information, worker biometric information, equipment operation information, and quality information of manufactured products, it is possible to set an abnormal risk condition, and it is possible to improve the risk so that the work is efficient and for the accurate performance. In addition, all data collected from cameras and IoT sensors inside the smart factory are processed by the AI edge device instead of all data being sent to the cloud, and only necessary data can be transmitted to the cloud, so the processing speed is fast and it has the advantage that security problems are low. Additionally, the use of AI edge devices has the advantage of reducing of data communication costs and the costs of data transmission bandwidth acquisition due to decrease of the amount of data transmission to the cloud.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.525-534
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• 2010

A road curbstone is a structure installed at the boundary of the sidewalk and the street with the objectives of road drainage, drawing attention and such. The current general construction method of curbstones places foundation concrete for the curbstones first, waits until the concrete reaches the strength to support the curbstones, places the curbstones on top, and then places the gutter and rear filling concrete. Such method has the issues of poor compaction and weakened bond strength of concrete due to split placing of concrete, and causes the curbstones to easily separate due to vehicle impact or earth pressure, in turn creating maintenance costs and spoiling the aesthetics. To improve such conventional construction methods, an all-in-one method was developed using formwork rail and jig where both the curbstones and gutter can be worked at the same time, and to evaluate the structural performance, static tests of lateral loading test, pullout test, and bending test were executed, and dynamic tests such as pendulum test and actual vehicle impact test were executed. In all tests, the all-in-one construction method using formwork rail and jig was shown to be superior to the conventional construction method by the increase of construction quality and bond strength of concrete.

• Korean Journal of Organic Agriculture
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• v.15 no.3
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• pp.319-330
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• 2007

This study analyzed physical and chemical characteristics of peat soil to use peat soil as the materials fur pot media and investigated seedling quality of horticultural plants in order to use peat soil as the raw materials fur pot media. The summary of the results is as follows; The chemical characteristics of peat soil, which is main ingredient of pot media are as follows; pH was 4.9, EC was less than $2.0ds{\cdot}m^{-1}$, which interferes the growth of the plant and organic ingredient was 33%. When looking into the germination characteristics of plants according to the mixture of pot media, red pepper showed 54.2% speed of germination and 97% germination rate in peat soil single treatment. Therefore the peatsoil was appropriate for the pot media for red pepper. In case of cucumbers, in the 50 : 50 treatment of main ingredient (peat soil) and auxiliary ingredients (vermiculite, peat moss and perlite) they showed 100% speed of germination and 100% germination rate. Therefore 50 : 50 treatment was appropriate fur the pot media for cucumbers. In case of chinese cabbage, peat soil, perlite and peat moss mixture (50 : 25 : 25) treatment showed the highest speed of germination (77.5%), while the germination rate was a little lower (92.15%) than comparative soil. However, it was appropriate for the pot media for chinese cabbage. In case of watermelon, germination was bad because of the influence of EC when the teat soil ingredient is over 80%. However, in the mixture of peat soil and vermiculite (50:50) treatment, they showed 91.6% speed of germination and 100% germination rate. Therefore it was appropriate for the pot media for watermelon. When looking into the growth of the plants according to the mixture of ingredients, peat soil and perlite (50:50) mixture showed excellent seedling quality for cucumbers, peat soil and perlite (50:50) mixture showed excellent seedling quality and it was proven to be appropriate for the pot media for cucumbers. In case of watermelon, peat soil, peat moss and perlite (80 : 10 : 10) mixture showed excellent seedling quality and it was proven to be appropriate for the pot media for watermelon.

• Korean Journal of Community Nutrition
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• v.26 no.5
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• pp.327-336
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• 2021

Objectives: This study was conducted to create a 3D printable snack dish model for the elderly with low food or fluid intake along with barriers towards eating. Methods: The decision was made by the hybrid-brainstorming method for creating the 3D model. Experts were assigned based on their professional areas such as clinical nutrition, food hygiene and chemical safety for the creation process. After serial feedback processes, the grape shape was suggested as the final model. After various concept sketching and making clay models, 3D-printing technology was applied to produce a prototype. Results: 3D design modeling process was conducted by SolidWorks program. After considering Dietary reference intakes for Koreans (KDRIs) and other survey data, appropriate supplementary water serving volume was decided as 285 mL which meets 30% of Adequate intake. To consider printing output conditions, this model has six grapes in one bunch with a safety lid. The FDM printer and PLA filaments were used for food hygiene and safety. To stimulate cognitive functions and interests of eating, numbers one to six was engraved on the lid of the final 3D model. Conclusions: The newly-developed 3D model was designed to increase intakes of nutrients and water in the elderly with dementia during snack time. Since dementia patients often forget to eat, engraving numbers on the grapes was conducted to stimulate cognitive function related to the swallowing and chewing process. We suggest that investigations on the types of foods or fluids are needed in the developed 3D model snack dish for future studies.