• Proceedings of the KSME Conference
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• 2001.11b
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• pp.776-781
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1MW organic Rankine cycle system was designed and developed. The exhaust gases of $175^{\circ}C$ at two 100MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1MW as designed but only 670kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.79-84
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• 2012

This study consist of two parts. One is development of a self-propelling vinyl remover which was already reported at the previous paper. This is the second part of the study. For the study, an attached vinyl remover was developed. It was consisted of connecting tractor to bucket, removing bucket from tractor, and the process was the tractor's assistance hydraulics. In the case of an attached vinyl remover, the vinyl was twisted 0.5times per 30~85cm length. The bobbin's diameter was 190mm and it's stable travelling speed was 1m/s. The revolution of the remover wheel was 90rpm to maintain the wheel's linear velocity. As seen at performance test at the field which had 950mm ridge intervals and 10 a area, the average working speed was 1m/s and the turning time was 20seconds. Therefore, the working performance was 24.5min/10a. The efficiency of used vinyl remover was 97% and working conditions were good.

• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.125-129
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• 2014

The paint removal and recoating are the very important process in airplane maintenance. The traditional technology is to use the chemical way corroding the paint with paint remover. For changing the defects, corrosion & pollution & manual working, of the traditional technology, the physical process which removes the paint of airplane with 250MPa/250kW ultra-high pressure rotary water jetting though the surface cleaner installed on the six axes robot is studied. The paint layer of airplane is very thin and close. The contradiction of water jetting paint removal is to remove the paint layer wholly and not damage the surface of airplane. In order to solve the contradiction, the best working condition must be reached through tests. The paint removal efficiency with ultra-high pressure and move speed of not damaged to the surface. The move speed of this test is about 2m/min, and the paint removal efficiency is about $30{\sim}40m^2/h$, and the paint removal active area is 85-90%. No-repeat and no-omit are the base requests of the robot program. The physical paint removal technology will be applied in airplane maintenance, and will face the safety detection of application permission.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.699-705
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• 2011

A combined heat and power cogeneration system driven by low-temperature sources is investigated by the first and second laws of thermodynamics. The system consists of Organic Rankine Cycle (ORC) and an additional process heater as a series circuit. Seven working fluids of R152a, propane, isobutane, butane, R11, R123, isopentane and n-pentane are considered in this work. Maximum mass flow rate of a working fluid relative to that of the source fluid is considered to extract maximum power from the source. Results indicate that the second-law efficiency can be significantly increased due to the combined heat and power generation. Furthermore, higher source temperature and lower turbine inlet pressure lead to lower second-law efficiency of ORC system but higher that of combined system. Results also show that the optimum working fluid varies with the source temperature.

• International Journal of Fluid Machinery and Systems
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• v.5 no.1
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• pp.38-48
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• 2012

One centrifugal compressor is applied for refrigeration and its working substance is R134a. The operating points obtained by using similar conversion at different rotation speeds are compared with the numerical results. They keep consistent with each other while the rotation speeds are lower, but the error between them will become large with the increasing of the rotation speed. Then the operating points are obtained when the working substance is air by using two similar conversion methods separately. Based on the comparison, it can be obtained that the result of keeping the specific volume ratio of inlet and outlet is more accurate than the result of maintaining Ma number. Then the test result is compared with the similarity result and the numerical result when the working substance is air. It is obtained that the similarity result is more consistent with the test result better than the numerical result and the trend of efficiency and pressure ratio change with the flow rate is consistent with the test result. In the process of similar conversion, the efficiency ${\eta}$ is no useful for similitude design and it has less influence on the conversion result.

• International Journal of Highway Engineering
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• v.14 no.5
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• pp.157-164
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• 2012

PURPOSES: Regional offices of the Ministry of Land, Transport and Maritime Affairs use a computerized system called KAMIS so as to manage road equipment systematically. Road agencies can record number of operating days by equipment, actual working hours, accumulated operating hours (or distance) by equipment, and operating cost. However, KAMIS does not provide critical information, although it is strongly related to efficient road management equipment operation. In other words, road agencies do not know whether they have sufficient equipment to handle their actual work. METHODS: Therefore, this study suggests a methodology to evaluate for operational efficiency of road management equipment using analytical hierarchy process(AHP). First of all, estimated weights related criteria can be produced by AHP, and then use operational history by pieces of equipment. RESULTS: Results show that importance of management work can differ from weather conditions through five areas. CONCLUSIONS: Commonly, this results can imply to help save money for the purchase and maintenance of road management equipment, and they would improve the functional performance of KAMIS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1193-1215
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• 2021

The measurement of the key product quality index plays an important role in improving the production efficiency and ensuring the safety of the enterprise. Since the actual working conditions and parameters will inevitably change to some extent with time, such as drift of working point, wear of equipment and temperature change, etc., these will lead to the degradation of the quality variable prediction model. To deal with this problem, the selective integrated moving windows based principal component regression (SIMV-PCR) is proposed in this study. In the algorithm of traditional moving window, only the latest local process information is used, and the global process information will not be enough. In order to make full use of the process information contained in the past windows, a set of local models with differences are selected through hypothesis testing theory. The significance levels of both T - test and χ² - test are used to judge whether there is identity between two local models. Then the models are integrated by Bayesian quality estimation to improve the accuracy of quality variable prediction. The effectiveness of the proposed adaptive soft measurement method is verified by a numerical example and a practical industrial process.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.1
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• pp.100-107
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• 2018

Objectives: This study examines exposure to hazardous substances in the working environment caused by exposure to toxic substances produced in the aluminum die casting process in the automobile manufacturing industry. Materials and Methods: The exposure concentration levels, detection rates and time-trend of 15 hazardous factors in the aluminum die casting process over 10 years(from 2006 to 2016) were used as a database. Results: The study found that hazardous factors in the aluminum die casting process were mostly metals. The rate for detected samples was 70.6%(405 samples), and that for not detected samples was 29.4%. The noise for an eight-hour work shift showed a 49.7% exceedance rate for TLV-TWA. Average noise exposure was 89.0 dB. The maximum exposure level was 105.1 dB. Conclusion: The high numbers of no-detection rates for hazardous substance exposure shows that there is no need to do a work environment measurement. Therefore, alternatives are necessary for improving the efficiency and reliability of the work environment measurement. Moreover, to prevent noise damage, reducing noise sources from automation, shielding, or sound absorbents are necessary.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.69-79
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• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.

• Korean Journal of Construction Engineering and Management
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• v.19 no.5
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• pp.61-69
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• 2018

Construction projects consist of long-term on-site production, and most disciplines are featured by outdoor works. Therefore, when a process plan is established, non-working days are calculated and reflected in a process schedule to comply with the planned construction period. However, necessary information and working methods are different in the course of the work, so the method of calculation varies depending on persons even for the same site, and the result is also very different. Therefore, scientific and quantitative understanding of business information is needed. This study reconstructed non-working day estimation process by collecting and organizing the information necessary for non-working day estimation, and designed the demonstration screen based on the reconstructed process and verified through expert interview at each stage. As a result, it showed about 69% reduction of work time and reliability of 92% work information matrix, and 80% of the experts evaluated the systemization of the relevant work. This study is expected to improve the understanding of work and increase the efficiency of work performance, and the study on systemization in the future should be continued.