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무윤활 상태에서 3D 프린팅용 PLA 및 PETG 소재의 마모 현상에 관한 연구
조연상,이현섭 한국정밀공학회 2024 한국정밀공학회지 Vol.41 No.2
With the recent development of 3D printing technology, various 3D printing materials have been developed and used. To utilize 3D-printed products with mechanical parts, studies on friction and wear characteristics according to relative motion between materials are required. However, tribology studies on 3D-printed materials are limited compared to those of the existing materials for mechanical parts. In this study, the frictional and wear characteristics are identified through a reciprocating wear test in non lubricated conditions between the Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PETG) printed in the Fused Deposition Modeling (FDM) method. In the wear test between the same materials, the friction coefficient and wear rate were higher in the PLA than in the PETG, and PLA was deposited on the block due to high frictional heat. In the wear test of the PLA block and PETG bump, the wear of the PLA block decreased compared to the wear test between the same materials, but the wear of the PETG bump tended to increase. Therefore, it seems that the 3D-printed PETG may be more advantageous in terms of friction and wear than 3D-printed PLA during relative movement in a non lubricating condition.
조연상 한국지방재정학회 2010 한국지방재정논집 Vol.15 No.2
Personnel expenditures account for a large, inflexible amount of the budgets of local government. Various attempts have been made to decrease personnel expenditures (wages and salaries) in the local governments. However, no attempts have been made to discover the most rational or efficient size of budget, nor to find the determining factors of personnel expenditures. This article is focused on finding the determining factors of personnel expenditures in lower tier governments in Korea. To find the determining factors of personnel expenditures, I tested the regression analysis model which is composed of per capita personnel expenditures and per capita area, and then investigated outliers from the regression line. In the course of testing outliers, I found that 'the congestion costs' and 'the remote place costs' had influenced the size of personnel expenditures in lower tier governments. Using the adjusted regression analysis model in which 'the congestion dummy variables' and 'the remote place dummy variables' were included, I could prove that this model was a good fit.
민선자치시대의 재정평가 연구: 충청남도 민선 1-3기를 사례로
조연상 한국지방재정학회 2005 한국지방재정논집 Vol.10 No.2
This article is aimed to evaluate the Fiscal Management of Chungnam Province during 1995-2003. J.M. Buchanan(1950) has adopted the concept of horizontal equity to fiscal benefits from public goods as well as to tax burden. In the view of each individual person, horizontal equity means fiscally "wherever he lives, his Fiscal Benefit/Burden is equal to the other's one". In this paper I have defined Residents' Burden as residents' tax burden devided by per capita GRDP. And I have defined Fiscal Benefit as total expenditures devided by the products of UCC(Unit Cost Coefficient) and CCC(Congestion Cost Coefficient). have developed some useful indices (including Residents' Burden Index, Fiscal Benefit Index, Fiscal Benefit/Burden Index, Unit Cost Coefficient, Congestion Cost Coefficient) to evaluate horizontal equity between resident who lives in Chungnam Province and who lives in different areas.
조연상,김영희,박흥식 한국기계가공학회 2008 한국기계가공학회지 Vol.7 No.4
The fractal dimension aims to quantitatively define the irregular characteristics of the shape in nature. It can be useful in describing morphological characteristics of various wear particles. This paper was undertaken to diagnose failure condition for sliding members in lubrication using fractal dimension. The experiments were undertaken to analyze the shape of wear particles and to diagnose failure condition for sliding members in lubrication using the image processing and the fractal parameters. It was possible to diagnose wear mechanism, friction, and damage state of machines through analysis of shape characteristics for wear particle in driven condition using fractal parameters.
조연상 한국재정학회 1991 재정논집 Vol.5 No.-
This paper is aimed at analysing the structure and the characteristics of state expenditure and revenue of Korea in the viewpoint of political economics, following the approach of fiscal crisis theorists. Major empirical findings are as follows: First, state expenditure(including tax expenditure and various funds) has continuosly increased and especially the ratio of expenditures for accumulation(social investment) has been very high. Second, fiscal deficit in consolidated public sector has continued until 1986 in spite of steadily increasing revenue. Third, public debts caused by fiscal deficit expansion have been accumulated, and it has affected chronic inflation. But on the revenue side, we can observe different aspects in view of there being a limitation to increasing revenue. In my opinion, this phenomenon has occured because of the oppressed labor union. I really found that tax revenue has been collected mainly from laborer rather than capital. In paticular we found that the rate of tax exploitation in O'Connor-Miller term has been very high and rapidly increasing.
조연상,배명호 한국트라이볼로지학회 2019 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.35 No.1
The differential planetary gear reducer as a main component of the concrete mixer driving mechanism requires a strong torque to mix concrete compounds. As this component is currently dependent on imports, it is necessary to develop it by conducting a study on vibration analysis and the resonance problem. The noise and vibration of a concrete mixer reducer increase owing to the transmission error of planetary gears, and the damage of components occurs owing to the problems in design and production. In this study, the tooth-passing frequency is calculated to evaluate the noise and vibration of a mixer reducer, and a fast Fourier transform (FFT) analysis is conducted through a vibration test using an acceleration sensor. The vibration of the reducer is measured at three points of input and output of the shaft and planetary gear housing with fixed and variable revolutions per minute. The operating conditions of gears and bearings are evaluated by performing the FFT analysis, and the resonance problem is verified. The results show that No. 1 pinion and ring gears revolve disproportionately. The amplitude values appear high, and the wear of tooth faces occur in tooth-passing frequencies and harmonic components of No. 1 and No. 2 pinion-ring gears. Therefore, we conclude that design changes in the reducer and a correction of tooth profiles are required.