• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.816-824
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• 2003

In this study, variations of cutting performance with pulse time, open circuit voltage, wire speed and dielectric fluid pressure were experimentally investigated in Wire Electrical Discharge Machining (WEDM) process. Brass wire with 0.25 mm diameter and AISI 4140 steel with 10 mm thickness were used as tool and work materials in the experiments. The cutting performance outputs considered in this study were surface roughness and cutting speed. It is found experimentally that increasing pulse time, open circuit voltage, wire speed and dielectric fluid pressure increase the surface roughness and cutting speed. The variation of cutting speed and surface roughness with cutting parameters is modeled by using a regression analysis method. Then, for WEDM with multi-cutting performance outputs, an optimization work is performed using this mathematical models. In addition, the importance of the cutting parameters on the cutting performance outputs is determined by using the variance analysis (ANOVA).

• Journal of ILASS-Korea
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• v.25 no.3
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• pp.111-118
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• 2020

This paper describes the effect of DME, biodiesel blended fuels on the macroscopic spray characteristics in a high pressure diesel injection system using Background Oriented Schlieren (BOS) method. The BOS method for visualization of impingement evaporation sprays to analyze macroscopic spray properties and evolutionary processes. In this work, the blending ratio of DME in the blended fuel are 0, 50, 100% by weight ratio. In order to investigate the macroscopic impinged spray characteristics under the various injection parameters and blending ratio. In this work, a mini-sac type single-hole nozzle injector with nozzle hole was length 0.7 mm and diameter of 0.3 mm was used. According to the result, the spray area of the collision wall increased as the DME mixing ratio increased, and the evolutionary pattern showed a stepwise increase due to the collision effect of the wall. Also, results of impinged spray area were increased according to increasing injection pressure.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.72-77
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• 2010

During the period of reinforcement work for the licensing renewal of CANDU NPP, the fuel channels, Calandria tubes and feeders of CANDU Reactor are replaced. The remote visual inspection of Calandria internal is also performed during the period of reinforcement work. This period is a unique opportunity to inspect the inside of the Calandria. The visual inspection for the Calandria vessel and its internals of Wolsong NPP Unit 1 was performed by Nuclear Engineering & Technology Institute(NETEC) of KHNP. To perform this inspection, NETEC developed equipment applied new technology such as the synchronization of 3D CAD, automatic alignment and control system. The inspection confirmed that the Calandria integrity of Wolsong NPP Unit 1 is perfect.

• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.1-6
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• 2002

A dynamic characteristics of shock absorber in the various excitation is investigated experimentally. Work diagrams and characteristic curves are used as a experimental standard. The various excitation conditions temperature and noise are very important factors in associated with the reduction of damping force. It is found that the heat occurrence from shock absorber, the gas shock absorber is much higher than oil shock absorber and increased in high speed. As to the variation of damping force, there are no change when the speed is low but we fixed amount of variation by increasing speed and change of new and old decrease. The sound pressure of the swash noise from cycle of shock absorber, we compared with theory sound pressure by experiment.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.4
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• pp.137-146
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• 2000

The hydraulic energy regnerative brake systems is introduced in this work. An accumulator stores kinetic energy during braking action, and the stored energy is used in a following acceleration action. The dynamic model of the brake system is derived for computer simulation study, and the Runge-Kutta numerical integration method is applied to the simulation work. Since the model contains several unknown parameters, these were determined by data which had been proceeded. Through a series of computer simulation , dynamic performance of the energy regenerative brake system is compared with that of a conventional system in which a conventional brake circuit is used. A series of test is carried out in the laboratory. The dynamic characteristics of the hydraulic motor system, such as the surge pressure and response time, are investigated in both brake action and acceleration action.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.5-12
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• 2009

The present work aims to estimate channel, shell, tube and tube sheet stresses of shell and tube oil cooler stemmed from various parameters. These parameters involve size, thickness and dimension of shell and tube oil cooler, including fluid temperature. The main purpose of the present work is to ensure safety of design products and also develop new products rapidly. For stress evaluation of oil coolers, first of all, the maximum pressure on the shell-side and on the tube side is fixed with 3.1MPa and 1.5MPa, respectively. Secondly, the pressure on each side varies from 2MPa to 3.1MPa on the shell side and tram 0.6MPa to 2MPa on the tube side. Various parameters under these conditions are employed to estimate design stresses on each side of oil cooler. These basic information related to stresses will be useful for a designer or manufacturer of an oil cooler.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.272-277
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• 1998

Chemical-Mechanical Polishing (CMP) refers to a material removal process done by rubbing a work piece against a polishing pad under load in the presence of chemically active, abrasive containing slurry. CMP process is a combination of chemical dissolution and mechanical action. The mechanical action of CMP involves tribology. The liquid slurry is trapped between the wafer(work piece) and pad(tooling) forming a lubricating film. For the first step to understand material removal rate of the CMP process, the lubricational analyses were done with commercial 100mm diameter silicon wafers to get nominal clearance of the slurry film, roll and pitch angle at the steady state. For this purpose, we calculate slurry pressure, resultant forces and moments at the steady state in the range of typical industrial polishing conditions.

• Tribology and Lubricants
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• v.15 no.1
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• pp.90-97
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• 1999

Chemical-Mechanical Polishing (CMP) refers to a material removal process done by rubbing a work piece against a polishing pad under load in the presence of chemically active, abrasive containing slurry. CU process is a combination of chemical dissolution and mechanical action. The mechanical action of CMP involves tribology. The liquid slurry is trapped between the wafer (work piece) and pad (tooling) forming a lubricating film. For the first step to understand material removal rate of the CMP process, the lubricational analyses were done with commercial 100mm diameter silicon wafers to get nominal clearance of the slurry film, roll and pitch angle at the steady state. For this purpose, we calculate slurry pressure, resultant forces and moments at the steady state in the range of typical industrial polishing conditions.

• Advances in aircraft and spacecraft science
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• v.5 no.5
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• pp.533-550
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• 2018

Detonation transmission between propane/oxygen (donor) and propane/air (acceptor) with an abrupt area change is experimentally studied. In the donor, there are two types of incident detonation waves: A self-sustained Chapman-Jouguet (CJ) detonation wave and an overdriven detonation wave that is a result of the difference in the initial donor pressure ratios. The piston work is used to characterize the strength of the incident detonation wave. For an incident CJ detonation wave, the re-initiation of a detonation wave in the acceptor depends on the initial pressure in the donor and the expansion ratio. The axisymmetric and non-axisymmetric soot patterns respectively correspond to direct detonation and detonation re-initiation. For an incident overdriven detonation wave, the re-initiation of a detonation wave in the acceptor strongly depends on the degree of overdrive.

• The Journal of Pediatrics of Korean Medicine
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• v.4 no.1
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• pp.1-17
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• 1990

?In order to investigate effects of Zanthoxyli Fructus (Sample-A) and Fagarae mandshuricae Fructus (Sample-B), experimental study was performed through observation on isolated - ileum analgesic, hypothermal, anti-pyretic, anti-inflammatory, capillary permeability, blood flow rate, blood pressure and respiratory works. The results were as follows; 1. In spontaneous movement of mice isolated-ileum, both samples were noted to have strong inhibitory action after temporary contraction, and to show antagonism against acetylcholine chloride and barium chloride. 2. Both samples were showed to have antihistamin work on guinea pig isolated-ileum 3. In analgesic work by the acetic acid method, only Fagarae mandshuricae Fructus was proved to have significant analgesic effect in mice. 4. Both sample groups indicated anti-pyretic and anti-inflammatory effect. 5. Both samples were noted to have inhibitory effect against capillary permeability ?rise in mice. ?6. Both samples were noted to have dose-dependent falling effect on blood pressure in rabbits.