• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.143-150
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• 2006

Recently, in proportion to increased demand on environmentally-friendly heat source, efficient management of district heating(DH) system becomes one of important issue. The objectives of this paper are to systematize data processing of transition temperature, investigate the effect of temperature variations on thermal fatigue and find out a way to improve design fractures of Korean DH pipes. For this purpose, reliable fatigue lift evaluation procedures are examined and applied to quantify thermal fatigue lives. Also, as a prototypal optimization analysis results, mean value of original cross sectional area of selected pipes was reduced 18.6% sustaining their sufficient margins against fatigue failure. So, it is anticipated that the output of this research can be used as useful information of optimal design and operation in the future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.106-111
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• 2007

In this study, we designed a digital fuzzy logic controller based on FPGA and microprocessor for MPPT of the sofar power generation system. A fuzzy algorithm to control the power tracking function of a boost converter has been built into the FPGA, and applied to the small scaled solar power generation system. The embodied controller showed a stable operation characteristic with the small output voltage ripple for the intensity change of solar radiation. This result proves that the implementation of the power tracking controller using FPGA is an effective way compared to the existing one using microprocessor.

• International Journal of Railway
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• v.9 no.2
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• pp.27-35
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• 2016

In spite of recent advances in ballasted railway track, the correct choice of ballast for rail track is still considered critical because aggregates progressively deteriorate under traffic loading and environmental exposures. Various ballast requirements, functions and duties have been defined by researchers, railway companies and countries' regulations even though it needs to be integrated to make following proper decision during track operation and maintenance. A proper understanding of ballast properties and suitable tests are prerequisites for minimizing maintenance costs. This paper presents a capable classification for ballast characteristics which need to be investigated beforehand to such a way, firstly to assign ballast functions, secondly need to clarify ballast requirements, thirdly to map appropriate tests to evaluate ballast characteristics and then it must be such that if ballast cannot carry out one of these duties, be able to call there is ballast defect. The paper is structured in order to achieve these objectives.

• Journal of Korean Academy of Nursing
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• v.14 no.2
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• pp.12-18
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• 1984

The purpose of this study was to compare educational needs following open heart surgery assessed by nurses & patients themselves, Data were collected from Nov. 1983 to Jan. 1984 through administration of Questionnaire developed for this study by the researcher. The subjects were 45 patients who experienced open heart surgery and 29 nurses who taking care of these patients in chest surgery ward at Seoul National University Hospital. The Data were analyzed by T-test and One Way ANOVA according to dependent variables. The result were as follows 1. There are significant difference between educational needs, assessed by nurses and patients themselves. (p<0.05) The nurses reported higher score of educational needs than patients. 2. In comparison of content area of educational needs, there was significant difference according to respiratory care, fain, chest tube care and operation including heart function between two groups. But, there was no significant difference in diet, activity, complication, emotional care and medication between two groups. 3. The priorities in content area of educational needs rated by nurses and patients were similar.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.497-501
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• 2000

One of the way to derive design parameters of the fuel feeding system in satellite is to analyze unsteady flow of liquid propellant (hydrazine) in the propulsion system. During steady thruster firing the flow rate is constant: if a thruster valve is abruptly shut down among a sets of thrusters, pressure spikes much higher than the initial tank pressure occur. This renders the fuel flow unsteady, and the fluid pressure and flow rate to oscillate. If the pressure spikes are high enough, there are possibilities that propellant explosively decomposes, thruster valves are damaged, and adiabatic detonation of the hydrazine propellant is potentially incurred. Reflected shockwaves could also affect the calibration and operation of the pressure transducers. These necessitate the analysis of unsteady flow in the propulsion system design, and the calculation results obtained through some governing parameter variation are presented in this work.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1709-1716
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• 2003

Stirling engine is a heat engine with a high potential efficiency, multi-fuel capability, its low emission, quiet operation, very low maintenance requirement and long life. The Stirling cycle can ideally achieve optimum thermodynamic efficiency of the Carnot cycle. But the actual efficiency of practical reciprocating Stirling engine is much less than that of ideal Stirling cycle due to several mechanical limits. This paper presents a new-type Stirling engine employing the scroll mechanism superior to the reciprocating Stirling engine. The new-type Stirling engine is characterized as traits of continuous and wholly seperated compression and expansion, one-way flow, direct cooling and heating through the extensive surfaces of scroll wraps. By means of this traits, the new-type Stirling engine can achieve thermodynamic cycle closer to the ideal Stirling cycle and have many mechanical merits. Also, the new-type Stirling cycle can be applied as Stirling refrigerator and Duplex Stirling machine.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.497-501
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• 2009

When modal tests on the large structures and machinery are performed, it is in general difficult and inaccurate to use artificial excitation devices such as impact hammers, because of insufficient capacity of the device and different environmental conditions of the concerned structures. Therefore, the Operational Modal Analysis(OMA) technique, which is performed by measuring only vibration responses during the operation of the objective product, can be one alternative. In this paper, the way to identify natural frequencies, mode shapes and damping ratios of a ship by using the OMA during the sea trail is described.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.36-40
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• 2006

In order to prevent the environmental pollution, the dryers are commonly used to treat sludge that one of sewages is polluting the quality of water. Generally, the drying method is various as to the property of material and use. Rotary dryer is a good apparatus to treat them. It is the way that is to make substance transmission and heat using hot air between sludge particle and heated gas. In this paper, we developed a 3-pass rotary dryer for a design program for the 3-pass rotary dryer with various conditions. The working conditions of dryer are a raw sludge feed rate, input & output water content and operation time etc.

• Journal of the Korea Safety Management & Science
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• v.16 no.1
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• pp.45-52
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• 2014

The purpose of this study is to make sure what the stress causes of women's EMTs within the firehouse are, and is to suggest ideas (plans) that are possible to resolve this problem. The reasons are because of difficulties such as not only the overwork at one's tasks, the uncomfortable working environment and circumstances, women's pregnancy, but also shift work or the shift system. It's own ideas about the way to resolve these difficulties are as follows: a separate operation of first-aid department, environmental improvement within a fire house (fire station) via remodeling, activation of substitute man power, alterating women's EMT services into daywork system, mutual encouragement and solicitude among co-workers, reinforcement of the number of the working force to be mobilized, and adoption about the rest year system in employment.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.291-296
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• 2000

The crack of concrete induced by the heat of hydration is s serious problem, particularly in concrete structures such as bridge piers. thick walls, box type walls, mat-slab of nuclear reactor building, dams of foundations of high rise buildings, etc. As a result of the temperature rise and restriction condition of foundation, the thermal stress which way induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which consider steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis, Secondly it shows the application of the cracks control technique like the bottom of No.15,16 Underground LNG Tank in Inchon.