• Transactions of Materials Processing
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• v.27 no.2
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• pp.123-129
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• 2018

In the present study, the mechanical behavior of the spray-formed high speed steel was investigated employing the internal variable theory of inelastic deformation. Special attention was focused on the effect of the microstructure evolution during the hot working process, such as the distribution of carbides to provide a basic database for the production condition of high speed steels with excellent properties. The billets of high speed steel ASP30TM were fabricated by a spray forming, and the subsequently hot-rolled and heat-treated process to obtain uniformly distributed carbide structure. As noted the spray-formed high speed steel showed relatively coarser carbides than hot-rolled and heat-treated one with fine and uniformly distributed carbide structure. The step strain rate tests and high temperature tensile tests were carried out on both the spray-formed and the hot-rolled specimens, to elucidate their high temperature deformation behavior. The spray-formed high speed steel showed much higher flow stress and lower elongation than the hot-rolled and heat-treated steel. During the tensile test at $900^{\circ}C$, the interruption of the deformation for 100 seconds was conducted to reveal that the recovery was a main dynamic deformation mechanism of spray formed high speed steel. The internal variable theory of the inelastic deformation was used to analyze data from the step strain rate tests, revealing that the activation energies for hot deformation of as-spray-formed and hot-worked steels, which were 157.1 and 278.9 kJ/mol, and which were corresponding to the dislocation core and lattice diffusions of ${\gamma}-Fe$, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.101.3-101
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• 2002

Contents 1 Abstract- In the thermal power plant, there are six manipulated variables; main steam flow, feedwater flow, air flow, spray flow, fuel flow, and gas recirculation flow. Therefore, the thermal power plant control system is a multi-input and output system. In the control system, the main steam temperature typically is regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. Up to the present time, the PID controller has been used to operate this system. This paper focuses on the characteristic comparison of the PID controller, the modified 2-DOF PID Controller on the DCS, in order to design an optimal...

• Plant Journal
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• v.6 no.4
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• pp.63-71
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• 2010

The best way to prevent the corrosion of piston rod is a selection of quality of the material and method of construction which minimize the porosity. The high velocity oxy fuel(HVOF) method, which generates lower porosity than existing plasma spray, was applied to ceramic laminated bond layer. Porosity percentage fell to bellow 2%, lower than that of plasma spray at 7%. Coating material of ceramic-coated main layer was selected as the $Cr_2O_3$ affiliation material, which is more dense than $Al_2O_3$ affiliation. To fill up the pores formed after the coating process, we sealed the bond layer and main layer. Sealing process was performed twice, once after the coating and once after the grinding. Upon the anti-corrosion test on the sealed sample and on the non-sealed sample, it is confirmed that the sealed sample was not corroded for 1,000 hours while the non-sealed sample was corroded within 48 hours.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.553-559
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• 2006

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(volume of fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response In a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.569-576
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• 2023

An agricultural drones are gradually increasing in utilization due to economic efficiency, and consist of a main frame in charge of flying spray system in charge of moving pesticide to control targets. Therefore, the environment and characteristics of crops should be considered when controlling pesticides using drones and conditions such as systematic flying altitude of flight, speed, and spray time should be changed accordingly. However, pest control work using agricultural drones has different spray effects depending on level the operation proficiency and spray impact. In addition, there are variations in operating standards and control efficiency for agricultural drones, which hinder the distribution of agricultural control drones in the field of pest control work. Therefore, this study attempts to identify the spraying characteristics of agricultural drones, apply the effective spraying time, interval and experimentally verify the system that can calculation of spray area compared to previous studies. Through this experimental verification, it is intended to apply the optimal control process by minimizing the obstacles to pest control work by applying the operation method and systematic figures to agricultural drones.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.873-879
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• 2004

In all major industries ranging from powder industries and advanced ceramics, to the food and pharmaceutical manufacture powder industries, the main production process is the spray dryers. In this paper, a systematic approach is used and six rules are obtained for the basis of the fuzzy model. A fuzzy model is based on the past behavior of the target system and expected to be able to reproduce the behavior of the target system. The output of the developed fuzzy model shows, graphically and statistically, a high level of face validity. Therefore, it is concluded that the developed fuzzy model mimics the actual process and can be considered, with confidence, as a reliable model to study, analyze, and improve the existing process.

• Journal of ILASS-Korea
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• v.15 no.3
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• pp.124-130
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• 2010

Numerical simulation has been performed to investigate the mist flow characteristics through the fire suppression nozzles for the design purposes. The commercial softwares, FLUENT and the fire dynamic simulator, FDS with the proper modelings were chosen as the numerical tools. In order to find optimal conditions in sense of the main performances of nozzles, the spray characteristics were analyzed both inside and outside of the nozzles. Geometric factors of the injecting orifices, i.e., diameter and chamfered angle were chosen as the simulation parameters for design application. From the present numerical results, 1.0c nozzles, whose orifice-diameter was 1 mm, having the chamfered angles were shown as the best performance of the fire suppression.

• Tribology and Lubricants
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• v.26 no.3
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• pp.157-161
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• 2010

This study investigated the effects of spray parameters on wear behavior of the Ni-based hard coatings fabricated by thermal spray process. The experiment was designed by an orthogonal array, the Ni-based hard coatings were fabricated according to this experimental design. The wear test was performed on these coatings using ball-on-disk wear tester. The ANOVA was used to analyze the effects of spray parameters on the wear rate of these coatings, as a result, oxygen gas flow and acetylene gas flow were determined as main factors effected on the wear rate. The effects of these two factors on wear behavior were observed by using SEM and EDX.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.54-60
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• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.