• 통합자연과학논문집
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• 제12권3호
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• pp.74-77
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• 2019

The purpose of this study is to explore the effects of Chamaecyparis obtusa essential oil on the activity of autonomic nervous system. Heart rate variability (HRV), as an indicator of autonomic nervous system activity and blood pressure were measured before and after inhalation of Chamaecyparis obtusa essential oil. The systolic blood pressure was decreased by inhalation of Chamaecyparis obtusa essential oil (p<0.05). The diastolic blood pressure was not changed significantly by Chamaecyparis obtusa. High frequency (HF) power level was not changed but High frequency/Low frequency (HF/LF) ratio was decreased by Chamaecyparis obtusa essential oil (p<0.05), meaning that parasympathetic nervous system activity was not affected but sympathetic nervous system activity was decreased. These results indicate that Chamaecyparis obtusa essential oil has a modulatory effect on the autonomic nervous system activity.

• Food Science and Biotechnology
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• 제17권2호
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• pp.324-329
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• 2008

The effect of ultra-high pressure homogenization on the emulsifying properties of whey protein was investigated in a model emulsion made with whey protein isolate and soya oil under various pH. The emulsifying properties, the average diameter of the oil droplets ($d_{vs}$), and the protein load, were measured for each emulsion produced at different homogenization pressures (50 to 200 MPa) and pH values (4.6 to 8.0). According to the results of variance analysis and response surface, the pH had more influence on oil droplet size and protein load than homogenization pressure. The model equations, which were obtained by response surface analysis, show that pH and homogenization pressure had the major effect on oil droplet size and protein load. Higher homogenization pressure decreased the average droplet size and the protein load. Homogenization at high pressure, as opposed to low pressure, causes no overprocessing, but the effect was pH-dependent. The average diameter of the oil droplets increased slightly by decreasing the pH from 8.0 to 6.5 and then increased dramatically toward the isoelectric point of whey protein (i.e., at pH 4.6). Moreover associated droplets were found at acidic pH and their size was increased at high temperature.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.557-562
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• 2008

In this paper, experiments have been performed for the investigation of tribological characteristics of automobile gear oil with the addition of ZDDP and DEP by using the FALEX WEAR TEST MACHINE. The results are as follows. The wear characteristics of gear oil was improved by adding compound additives. The extreme pressure of gear oil increases and then decreases with the applied load. The maximum extreme pressure of gear oil with compound additive is bigger then that of pure gear oil. The friction coefficient of pure gear oil monotonically increases with the temperature, but that of gear oil mixed with the additives decreases at the high temperature.

• 한국해양공학회지
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• 제11권4호
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• pp.152-158
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• 1997

An analyzing method for pressure fluctuations in oil hydraulic pipe network was developed in this study. The object pipe network has multi-branch configuration, and the pipelines of it are composed of steel tubes, flexible hoses. Also, accumulators, orifices and lumped oil volume components are attached on it. Transfer matrix method, in other words impedance method, was used for the analysis. The reliability and usefulness of the analyzing method were confirmed by investigation computed results and experimental results got in this study.

• Journal of Biosystems Engineering
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• 제24권2호
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• pp.107-114
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• 1999

To find the best combustion conditions in the heavy oil burner kinetic viscosity of heavy oil A, B and C at different temperature range, from 40 to 140$^{\circ}C$, and the droplet sizes of the heavy oils at different temperature and pump pressure were measured. And, combustion characteristics were investigated under the different conditions : two different heavy oil and three different oil temperature. At temperature of 70, 100, 130$^{\circ}C$ the kinetic viscosity of heavy oil A and B are 7.9, 5.7, 4.3 and 30.4, 13.7, 7.9cSt, respectively. The greatest and smallest viscosity were 7,455 cSt at C oil on 27$^{\circ}C$ and 4.26cSt at A oil on 140$^{\circ}C$. The magnitude of viscosity difference between at 100$^{\circ}C$ and 140$^{\circ}C$ under 6 cSt in cases of A and B oil, but more than 30cST on C oil. Of the droplet sizes, the biggest and smallest droplet size in A oil were 98$\mu\textrm{m}$ at oil temperature of 130$^{\circ}C$(4.3cSt), pump pressure of 1.57MPa and 72$\mu\textrm{m}$ at 70$^{\circ}C$(7.9cSt), 2.35MPa, respectively. It appeared that as spraying pressure increased the droplet size decreased, however, no distinct differences were found in the effects of kinetic viscosity on the droplet sizes of the test range. The best combustion performance was observed when droplet size, spraying pressure and oil temperature were 73$\mu\textrm{m}$, 2.35MPa and 70$^{\circ}C$ producing CO2 of 13.1%, CO of 13ppm and flue gas temperature of 250$^{\circ}C$ in A oil combustion For B oil, it was100$^{\circ}C$, 2.35MPa, 52$\mu\textrm{m}$, producing CO2 of 10ppm and flue gas temperature of 260$^{\circ}C$. In general, it appeared that better combustion results were observed in the smaller droplets produced burner condition.

• Tribology and Lubricants
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• 제24권3호
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• pp.147-153
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• 2008

The effect of oil supply pressure on the performance of vapor cavitated short squeeze film dampers is examined. Vapor cavitation is characterized by film rupture occurring as a result of evaporating oils. The pressure of vapor cavity in the film is almost zero in absolute pressure and nearly constant. Pan's model about the shape of vapor cavity is utilized for studying the effect of vapor cavitation on the damping capability of a short squeeze film damper. As the level of oil supply pressure is increasing, vapor cavitation is suppressed so that the direct damping coefficient increases and the cross coupled damping coefficient decreases. Futhermore, the analysis of the unbalance responses of a rigid rotor supported on cavitated squeeze film dampers shows that a significant reduction in rotor amplitude and force transmissibility is possible by controlling the oil supply pressure into short squeeze film dampers.

• Journal of Power Electronics
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• 제9권5호
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• pp.800-808
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• 2009

This paper presents a practical method of pressure control for a hydraulic oil-pump system using an SR (Switched Reluctance) drive. For a 6Mpa grade hydraulic oil-pump, a 2.6kW SR drive is developed. In order to get high performance pressure dynamics in actual applications, a data based PID control scheme is proposed. The look-up table from a pre-measured data base produces an approximate current reference based on motor speed and oil-pressure. A PID controller can compensate for the pressure error. With the combination of the two references, the proposed control scheme can achieve fast dynamics and stable operation. Furthermore, a suitable current controller considering the nonlinear characteristics of an SRM (Switched Reluctance Motor) and practical test methods for data measuring are presented. The proposed control scheme is verified by experimental tests.

• International Journal of Air-Conditioning and Refrigeration
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• 제16권4호
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• pp.117-123
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• 2008

The present study is directed at flow and heat transfer of $CO_2$ and oil mixtures in a circular tube. PAG and POE oils are considered in this study. Flow characteristics of $CO_2$ and oil mixtures have been investigated by flow visualization. Pressure drop has been measured in the range of operating mass flow rate from 0.1 to 0.4 kg/min in a circular tube. Heat transfer characteristics of $CO_2$/oil mixtures have been investigated using a counterflow heat exchanger. In case of pure liquid $CO_2$ as well as $CO_2$ and POE mixtures, flow are seen to be uniform so that $CO_2$ and POE oil are still miscible even at flowing state. However, it is found that $CO_2$ and PAG are not miscible. Pressure drop of $CO_2$/PAG mixtures are much higher than that of $CO_2$/POE mixtures as well as pure $CO_2$ at a fixed mass flow rate. As the concentration of POE oil is increased from 0 to 5 wt%, pressure drop is increased. However, heat transfer rate and heat transfer coefficient of $CO_2$/POE mixtures are much higher than that of $CO_2$/PAG mixtures. The f-factor correlation and Nusselt number correlation for $CO_2$/POE oil mixtures are suggested in this paper.

• Tribology and Lubricants
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• 제21권6호
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• pp.249-255
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• 2005

In this paper, the friction characteristic of engine bearings has been analyzed in terms of a friction loss power, a minimum film thickness and an oil film pressure. This analysis has been focused on the fuel economy improvement with a low viscosity engine oil such as SAE 0W-40, which is used for a friction loss reduction and increased for a Diesel fuel economy. The friction loss power, the minimum oil film thickness and oil film pressure distribution for plain bearings of a Diesel engine are analyzed using an AVL's EXCITE program with a conventional engine oils of SAE 5W-40 and 10W-40, and a low viscosity engine oil of SAE 0W-40. The computed results indicate that a viscosity of engine oils is closely related to the friction loss power and the decreased minimum film thickness in which is a key parameter of a load carrying capacity of an oil film pressure distribution. When the low viscosity engine oil is supplied to engine bearings, it does not affect to the formation of a minimum oil film thickness. But the friction loss power has been significantly affected by low viscosity engine oil at a low operating temperature of 0. Based on the FEM computed results, the low viscosity engine oil at a low temperature range will be an important factor for an improvement of the fuel economy improvement.

• Tribology and Lubricants
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• 제24권1호
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• pp.21-26
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• 2008

A pin bush bearing is one of the most important element in the piston engine which is joined a piston to a connecting rod. A pin bush is suffered by heat and changeable repeat loads, which are come from the explosive gas heat and pressures during a reciprocating stroke. Therefore, a tribological behavior of pin bush bearings is very severe compared to other parts of a piston assembly. To keep a stable operation of pin bush bearings effectively, it would be satisfied with proper oil film strength for severe operating conditions and durability, which are strongly related to the oil film thickness, oil film pressure, and a friction loss power. The computed results show that the viscosity of engine oils slightly affects to the minimum oil film thickness and oil film pressure distribution, but is an influential parameter on a total friction loss power. Thus the low viscosity engine oils for an increased operation condition should select a high level of base oil and add a viscosity index improver as an oil film additive.