• International Journal of Automotive Technology
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• 제6권5호
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• pp.437-444
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• 2005

Unburned hydrocarbon (UBHC) emissions from gasoline engines remain a primary engineering research and development concern due to stricter emission regulations. Gasoline engines produce more UBHC emissions during cold start and warm-up than during any other stage of operation, because of insufficient fuel-air mixing, particularly in view of the additional fuel enrichment used for early starting. Impingement of fuel droplets on the cylinder wall is a major source of UBHC and a concern for oil dilution. This paper describes an experimental study that was carried out to investigate the distribution and 'footprint' of fuel droplets impinging on the cylinder wall during the intake stroke under engine starting conditions. Injectors having different targeting and atomization characteristics were used in a 4-Valve engine with optical access to the intake port and combustion chamber. The spray and targeting performance were characterized using high-speed visualization and Phase Doppler Interferometry techniques. The fuel droplets impinging on the port, cylinder wall and piston top were characterized using a color imaging technique during simulated engine start-up from room temperature. Highly absorbent filter paper was placed around the circumference of the cylinder liner and on the piston top to collect fuel droplets during the intake strokes. A small amount of colored dye, which dissolves completely in gasoline, was used as the tracer. Color density on the paper, which is correlated with the amount of fuel deposited and its distribution on the cylinder wall, was measured using image analysis. The results show that by comparing the locations of the wetted footprints and their color intensities, the influence of fuel injection and engine conditions can be qualitatively and quantitatively examined. Fast FID measurements of UBHC were also performed on the engine for correlation to the mixture formation results.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.110-116
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• 2005

Linear dynamic simulations with one and two degrees of freedom were built from SIMULINK in MATLAB commercial program. Before starting the simulations, initial conditions and system parameters which are mass, spring constant and coefficient of damping are easily inputted by user through each pop-up window, and the conditions for the simulation including time step, analysis methodology and so on can be modified with ease. Also, as soon as the simulations are started, the windows for animations which shows deformed motions dynamically with real time are popped-up and the graphical results are shown in time and frequency domains, simultaneously, The results of the simulations were verified through some examples of textbooks of mechanical vibrations. It was found that the programs would help us to solve any kind of linear dynamic simulation for one and two degrees of freedom.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.125-127
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• 2003

The single phase switched reluctance motor(SRM) is more simpler and robust in the structure than poly phase SRM. It has the merits that it reduces the switching elements and the energy density per volume is very high. Recently, it has been researched and developed in various types and starting method due to the technique of power electronics and the computer added design. The single phase SRM is tried to apply to many industrial appliance field to substitutethe the induction motor by the single phase SRM. On the previous studies, we decided the design parameters of the single phase SRM for the blower driver to adapt the design method of the conventional machine and the poly phase SRM. In this studies, it is proposed the conditions to decide the optimal pole arcs because the stator and rotor pole arcs is very important in the characteristics of the single phase SRM. For this reason, it is analysed the characteristics of current on/off angle vs. pole arc, pole arcs vs. average torque.

• 한국세라믹학회지
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• 제31권8호
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• pp.879-885
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• 1994

Coprecipitation technique was used to synthesize ZrO2+12 mol% CeO2 powders with ZrOCl2.8H2O and Ce(NO3)3.6H2O as starting materials. The powders were dried on different conditions such as distilled water, ethanol, and azeotropic distillation. The powders prepared by azeotropic distillation showed weak aggregation of particles and the average particle size of powders calcined at 85$0^{\circ}C$ for 1 hour was 0.19 ${\mu}{\textrm}{m}$. The optimum sintering temperature and holding time are 130$0^{\circ}C$ and 2.5~10 hours, respectively. Beyond the optimum conditions, a phase transition from tetragonal to monoclinic causes to produce cracks in the sintered bodies and to decrease the density.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.244-249
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• 2002

It is known that tip clearance flows reduce the pressure rin, flow range and efficiency of the turbomachinery. So, the clear understanding about flow fields in the tip region is needed to efficiently design the turbomachinery. The Navier-Stokes code with the proper treatment of the boundary conditions has been developed to analyze the three-dimensional steady viscous flow fields in the transonic rotating blades and a numerical study has been conducted to investigate the detail flow physics in the tip region of transonic rotor, NASA Rotor 67. The computational results in the tip region of transonic rotors show the leakage vortices, leakage flow from pressure side to suction side and their interaction with a shock Depending on the operating conditions, the position of shock-wave on the blade surface are v8y different close to the blade tip of the transonic compressor rotor. The shock-wave position dose to the blade tip had the dose relationship with the starting position of leakage vortex and the direction of leakage flow.

• 소음진동
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• 제5권3호
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• pp.345-352
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• 1995

A very simple and computationally efficient numerical method is developed for the free vibration of arbitrary shape plates. A set of two- dimensional simple series functions is used as an admissible displacement functions in the Rayleigh-Ritz method to obtain the natural frequencies for the arbitrary shape plates. From the prescribed starting function satisfying only the geometric boundary conditions, the higher terms in the series function are constructed with adding order of polynomial. Natural frequencies are obtained for the arbitrary shape plates, with combinational boundary conditions. The obtained numerical results are presented, some cases are verified with other numerical methods in the literature.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2000년도 춘계 학술대회 및 국제 감성공학 심포지움 논문집 Proceeding of the 2000 Spring Conference of KOSES and International Sensibility Ergonomics Symposium
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• pp.86-90
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• 2000

The effects of the timing of daily bathing on sleep in winter were studied. Eight healthy male subjects were assigned to three sleep conditions: bathing just before sleeping (Condition J), bathing 2 h before sleeping (Condition T0 and no bathing before sleeping (Control). We can found that slow wave sleep and REM sleep were increased, and sleep onset latency and wake after sleep onset were shortened in Condition T compared with Condition J. Rectal and mean skin temperatures n both bathing conditions were the same levels after the first half of sleep. Furthermore, subjective sleep sensation was the highest value in Condition T. These results suggest that bathing done before going to bed in winter was good for sleep; moreover, bathing 2 h before going to bed was more effective than bathing immediately before going to bed.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.779-790
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• 1993

A prototype of the feeding-milking robot was developed in the Hungarian Institute of Agricultural Engineering in 1988-89. Before starting with the operation tests the cleaning system had to be elaborated . The cleaning system has two parts. Those are the complete cleaning of the system, producing a practically sterile state, as well as flushing through the milking device between milking of two cows. Separate electronic sensor development was necessary for both system which can connect to the control system of the robot. To clean the system pneumatic air input was applied. As an effect of the local adjustment of the electronic control system optimal flow conditions can be formed what is more favourable comparing to the earlier solutions of cleaning due to the mechanical effect. In the flushing through overpressure air is applied. The air and the cleaning liquid input duration can be adjusted to the local conditions. The electronic control unit can be connected to the electric ircuits of robot.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.753-758
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• 1987

The purpose of ocean thermal energy conversion (OTEC) plant control is to provide stable power efficiently by appropriately regulating the seawater flow rates and the working fluid flow rate under conditions of continually changing seawater temperatures. This paper describes digital control of working fluid flow rate based on an adaptive control theory for the "Imari 2" OTEC plant at Saga University. Provisions have been made for linkage between the software of the adaptive control theory and the hardware of the OTEC plant. In implementing the working fluid flow rate control, if persistency of excitation conditions are lost, the algorithm of identification often exhibits bursting phenomena. To avoid this difficulty, the stopping-and-starting rule for identification was derived and was used for the working fluid flow rate control. Satisfactory control performance was then obtained by using this digital control system.ol system.

• 한국결정성장학회지
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• 제11권4호
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• pp.176-179
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• 2001

Iron oxide powders were prepared under high temperature (up to $175^{\circ}C$) and pressure conditions( up to 129 pasi) by precipitation from metal nitrates with aqueous potassium hydroxide. Various types of iron oxide powders were obtained at different conditions. The size and the shape of the particles can be controlled as afunction of starting solution pH. The average particles size of the synthesized iron oxide powders increased, the particle shapes of the powders became fibrous, and the crystalline phase of the powder changes from iron oxide to iron hydroxide with increasing solution pH. The effects of synthesis parameters are discussed.