• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.839-846
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• 2013

Because the performance of a reciprocating compressor in refrigeration and air-conditioning systems is influenced by the lubrication characteristics of sliding components, the lubrication characteristics between the crankshaft and journal bearing have to be researched for the design and the performance improvement of reciprocating compressors. Thus, the proper supply of lubricant for a lubrication between the crankshaft and journal bearing is essential, and an oil path for lubricant supply is installed in the shaft or bearing. However, in order to guarantee the lubrication performance of the journal bearing, it is necessary to design the position of the oil path. Therefore, it is studied to find the optimum position of the oil path by the analysis of the pressure distribution in the journal bearing. The results show that the position of the oil path is significantly influenced by the pressure distribution of the oil film in the journal bearing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.332-335
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• 1995

Electrification pipe modeled on the oil path of the high power transformer is designed and manufactured. Distributions of oil flow velocity are simulated as spacer form in the electrification pipe. Streaming currents are investigated as each electrification pipe. The surface oil velocity of spacer is small the streaming current.

• Food Science and Preservation
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• v.16 no.2
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• pp.246-252
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• 2009

Diacylglycerol(DAG) was produced by enzymatic esterification of glyceryl mono-oleate(GMO) and conjugated linoleic acid(CLA) in a stirred-batch type reactor. The reaction was catalyzed by lipozyme RMIM(an immobilized lipase from Rizomucor miehei). DAG was isolated by a short-path distillation process and decolorized. DAG oil was composed of 87.3% DAG, 11.4% triacylglycerol(TAG), and 1.5% monoacylglycerol(MAG)(all w/w). Major fatty acids in DAG oil were oleic acid(54%), CLA(31.1%), and linoleic acid(7%). DAG oil iodine,and acid values were 108.8, 2.57, and 1, respectively. The DAG oil solid fat index(SFI) and thermograms were obtained using differential scanning calorimetry.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.5
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• pp.38-44
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• 1992

In this paper, electrification pipe modeled on the oil path that insulating oil flow in the high power transformer is manufactured in order to prevent the accident cause from streaming electrification generated when insulating off flow at a solid-liquid interface, and the streaming current is measured and analyzed according to the shape of oil path in electrification pipe. From the result of this study, the streaming current increases linearly with increasing of a oil velocity and it increases at lower temperature and decreases at higher temperature than [$46^{\circ}C$]. The smoother the flow of insulating oil is the more the streaming current decreases.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.176-180
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• 1997

Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Flow is characterized into five categories according to its leakage path. Effect of geometry and leakage path are evaluated according to variation of sealing geometry. To simulate an oil jet or oil mist type high speed spindle lubrication, the working fluid is regarded as two phases that are mixed flow of oil phase and air phase. Both of the turbulence and the compressible flow model were introduced in CFD(Computational Fluid Dynamics) analysis. This offers a methodological way of enhancement seal design for high speed spindle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.114-119
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• 2016

This paper dealt with the propagation characteristics of acoustic signal in insulation oil for the purpose of improving the reliability of AE (acoustic emission) method used for condition monitoring of oil-immersed transformers. A discharge source was placed in insulation oil and AE sensors ($f_c$ :140 kHz) were attached on the oil tank to study the changes of velocity and propagation path with the depth and distance. The average velocity was 1,436 m/s and the velocity decreased with the increase of depth from the oil surface to 430 mm. The propagation paths were classified into three sections by the shortest reflection path of the detected signal. The minimum distinguishable distance in each section was 70 mm. It was also verified that PD (partial discharge) with a magnitude over than 500 pC can be detected by the AE sensors.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.4
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• pp.594-600
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• 1994

The maximum charge accumulation in transformers caused by streaming electrification is commonly observed on the bottom area of transformer winding(i.e.the oil inlet of transformer winding). It is because turbulent flows occur in this portion of transformers. Consequently, if we are to reduce the maximum charge accumulation of transformers, it is important that we should have a good understanding of the conditions of the occurence of partial turbulent flows in the oil inlet of transformer winding. With this point in mind, a simple flow model was designed in this study in order to simulate oil flow in the insulation ducts of power transformers. As a method for mitigating charge accummulation, attention was given to (a) a flow path design for the improvement of flow conditions, and (b) the charge tendency of the material used this design. The results of this study show that the above method is useful for mitigating charge accumulation.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.11-16
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• 1997

In the stroke sensitive shock absorber, the oil path is formed along the internal cylinder surface to make the oil flow during the piston's upper-lower reciprocation movement. In constrast with the conventional shock absorbesr which show one dynamic characteristic curve, stroke sensitive shock absorber shows two kinds of dynamic characteristics according to the stroke. In this study, in order to obtain more precise information about design and damping performance analysis, the analysis on the damping force generation process and dynamic behaviour characteristics of stroke sensitive shock absorber are performed by considering the valve characteristics.

• Asia-Pacific Journal of Business
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• v.15 no.3
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• pp.385-397
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• 2024

Purpose - The purpose of this study was to analyze the dynamic relationship between oil prices and macroeconomic variables (gross domestic product, consumer price index, and interest rate). Long-run and short-run effects of oil prices on these macroeconomic variables are examined. Design/methodology/approach - The vector error correction model (VECM) is used to examine the short-run and long-term causality of oil prices, and a hierarchical Bayesian vector autoregressive model (HBVAR) is used to find the impulse of oil shock and the response of other variables. Findings - First, oil prices do not have short-term causality with macroeconomic variables, but they have long-term causality with interest rates and GDP. Second, the long-term stable relationship of oil prices and other macroeconomic variables is important to find out causality. Third, oil shock increases interest rates and decreases GDP and consumer price. Research implications or Originality - The significance of this study is a new attempt to analyze the dynamic relationship between oil prices and macroeconomic variables by linking VECM and HBVAR. Although VECM can analyze the long-term relationship and short-term dynamics between oil prices and macroeconomic variables, it was difficult to identify the transmission path of the oil price shock. HBVAR is confirmed to be flexible because it can bypass the process of selecting VAR or VECM through unit root test and cointegration analysis, and it is expected to reduce uncertainty of selecting hyperparameters.

• The Journal of Korea Robotics Society
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• v.2 no.2
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• pp.161-167
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• 2007

It is dangerous that an inspector overhauls defects and condition of the inner parts of an oil tanker because of many harmful gases, complex structures, and etc. However, these inspections are necessary to many oil tankers over old years. In this study, we proposed the design of mobile robot for inspection of CAS in oil tanker. The developed CAS inspection mobile robot has four modules, a measurement module of oil tanker's thickness, a corrosion inspection module, a climbing module of the surface on a wall, and a monitoring module. In order to get over at a check position, the driving control algorithm was developed. Magnetic wheels are used to move on the surface of a wall. This study constructed a communication network and the monitoring program to operate the developed mobile robot from remote sites. In order to evaluate the inspection ability, the experiments about performance of CAS inspection using the developed mobile robot have been carried out.