• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1680-1686
• /
• 2009

Flow characteristics of a differential pressure flow meters which have a shape of triangular separate bar (TSB) was investigated according to machining conditions in pressure tapping holes. Size of pressure tapping holes is machined with either 1.0 mm or 1.5 mm in diameter. Also, number of pressure tapping holes are drilled either 9 or 17. The mass flow rate of the TSB flow meters are calibrated with a laminar flow meter by connecting them in line. The mass flow rate in the TSB flow meters are plotted with a non-dimensional parameter H which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters, and atmospheric pressure. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter H was obtained. The empirical correlation showed highly linear relationship between the mass flow rate and the non-dimensional parameter H. The hole size of the pressure tapping holes has a bigger effect on the flow rate than the number of the tapping holes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.17 no.4
• /
• pp.74-80
• /
• 2003

Ionic wind is produced by a corona discharge when a DC high voltage is applied across the point-to-plane gap geometry. The corona discharge phenomena have been investigated in several beneficial application fields such as electrostatic cooling, ozone generation, electrostatic precipitation and electrostatic spraying. Recently ionic wind might be used in aerodynamic, for example, heat transfer, airflow modification, and etc. In this work, in order to analyze the control behavior of the velocity and amount of ionic wind produced by the positive DC corona discharges. The ionic wind velocity was measured as a function of the applied voltage, diameter of the punched hole on plate electrode and separation between the point-to-plate electrodes. As a results, the airflow is generated from the tip of needle to the plate electrode in the needle-to-punched-plate electrode systems. The ionic wind velocity is linearly increased with an increase in applied voltage and ranges from 1 to 3 m/sec at the locations of 100-200 mm from the punched-plate.

• Carbon letters
• /
• v.19
• /
• pp.72-78
• /
• 2016

Spinnable pitches and carbon fibers were successfully prepared from petroleum or coal pyrolysis residues. After pyrolysis fuel oil (PFO), slurry oil, and coal tar were simply filtered to eliminate the solid impurities, the characteristics of the raw materials were evaluated by elemental analysis, ¹³C nuclear magnetic resonance spectrometer, matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS), and so on. Spinnable pitches were prepared for melt-spinning carbon fiber through a simple distillation under strong nitrogen flow, and further vacuum distillation to obtain a high softening point. Carbon fibers were produced from the above pitches by single-hole melt spinning and additional heat treatment, for oxidization and carbonization. Even though spinnable pitches and carbon fibers were processed under the same conditions, the melt-spinning and properties of the carbon fiber were different depending on the raw materials. A fine carbon fiber could not be prepared from slurry oil, and the different diameter carbon fibers were produced from the PFO and coal tar pitch. These results seem to be closely correlated with the initial characteristics of the raw materials, under this simple processing condition.

• Journal of Energy Engineering
• /
• v.13 no.2
• /
• pp.118-127
• /
• 2004

The purpose of this study is experimentally to analyze that intake port swirl, injection system and turbocharger have an effect on the engine performance and the emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement 16.7ι, and to suggest the improvement of engine performance. Generally to enhance engine power, TCI diesel engine is put to practically use turbo-charged intercoler in order to increase boost efficiency which is cooled boost air. As results of considering the factors of the intake port of swirl ratio 2.25, compression ratio 17.5, re-entrant 8.5$^{\circ}$ combustion bowl, nozzle hole diameter ${\Phi}$0.33*3+${\Phi}$0.35*2, nozzle protrusion 3.18mm, injection timing BTDC 12$^{\circ}$CA and turbo charger (compressor 0.6A/R+46Trim, turbine 1.0A/R+57Trim) is the best in the full range of operating in the engine performance and the exhaust characteristics of NO$\_$x/ concentration. Therefore their factors are appropriated as intake system, injection and turbocharger system.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.4
• /
• pp.406-414
• /
• 2001

Ultrasonic guided waves were explored to apply them to the long range inspection of polyethylene coated steel gas pipes. The steel pipes have such dimensions as 190.7mm inside diameter and 5.3mm thickness. The outside surface of the pipe is coated by a polyethylene layer of $1.9{\pm}0.5mm$ thickness. Non-axisymmetric guided waves were excited on the outside surface of the polyethylene coated pipe by using a 0.5MHz transducer with a variable angle shoe. Frequency and phase velocity tuning was used to find optimum guided wave modes for the inspection. The dispersive characteristics of the modes were analyzed in time-frequency representation obtained by short time Fourier transforms. Sample results were presented for artificial defects such as wall thinning and hole.

• Journal of radiological science and technology
• /
• v.21 no.1
• /
• pp.29-34
• /
• 1998

The purpose of simple abdomen erect projection is to see the fluid level which indicates gastrointestinal ileus or free air due to perforation. we do not have to insist on low kVp technique in simple abdomen erect position as long as we can detect the fluid level and free air shadow. Therefore, the author tried to decrease patient dose by high kVp technique and to improve the image quality due to motion artifact by reduction of exposure time. [Methods] Experiment 1. * screen/film SRO1000/HRH * exposure factor : $140\;kvp{\pm}5\;kv$ with added filters, 200 mA, 0.01 sec * phantom : Acryles : 15.0 cm(equivalent to 17 cm body thickness) 17.5 cm(equivalent to 21 cm body thickness) 20.0 cm (equivalent to 25 cm body thickness) With the exposure factor for same film density($D=0.8{\pm}0.1$) and with the materials above, we tried to find out entrance skin dose and gonad dose for both male and female. Experiment 2. Burger's phantom radiography were checked to see whether there was any change of image quality according to the kVp and the added filters. Experiment 3. Using rotating meter(self made), we examined the motion artifact and the exposure time limitation. [Results and conculution] 1. Using high voltage technique of 140 kVp with added filter, Skin dose, testicle dose and ovary dose decrease to 89.3%, 47% and 71.4% respectively compare to 70 kVp technique, 2. No great changes of Burger's phantom image has detected as from 70 kVp to 140 kVp and the air hole size of Burger's phantom over 0.028 cc(Diameter 3 mm, hight 4 mm) can be distinghished. 3. 0.01 sec(1 pulse) exposure time is possible in the single phase full wave rectification that why we can quitely reduce the unsharness caused by patient's movement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.540-543
• /
• 2011

This work is devoted to an experimental investigation on conceptual design of dual consecutive stage micro plasma thruster (${\mu}PT$). Optimization study on the thruster configuration has been performed for various electrode gap distances from 1 mm to 2 mm and the hole diameter from 0.3 mm to 2 mm depending on desired operating conditions and corresponding nozzle design requirement. The operation of ${\mu}PT$ at low pressure from $10^{-1}$ Torr to $10^{-4}$ Torr and at various argon flow rates ranging from 5 sccm to 300 sccm has been studied to understand the physic of plasma and the gas dynamics in details. The specific impulse can reach up to 3000-4000 seconds at low power consumptions from 1 to 5 W. Image of exhaust plume from ${\mu}PT$ will be provided and electrical characteristics is also mentioned in this paper.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.4-4
• /
• 2009

Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) was welded through a combination of a diode laser and CNC. Laser beam passed the transparent PC and was absorbed in an opaque ABS. Polymers were melted and welded by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead size and the specimen cross-section were analyzed, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was 3.75mm and the shear strength was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in CNC machining processes, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision. By combining two operations processes developed process gained 50% more efficiency.

• Progress in Medical Physics
• /
• v.30 no.4
• /
• pp.112-119
• /
• 2019

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber. Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose. Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively. Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.2
• /
• pp.64-76
• /
• 2009

Experimental and numerical studies are conducted on the characteristics of flame extinction and edge flame oscillation in counterflow diffusion flames. The characteristics of flame extinction and edge flame oscillation are well described varying burner diameter, separation distance between two burners, global strain rate, and velocity ratio. It is verified numerically and experimentally that radial conduction heat loss significantly contributes to flame extinction and edge flame oscillation at low strain rate flames in zero- and micro-gravity. It is also shown that for appropriately small burner diameters flame extinction modes are grouped into four and these are significantly attributed to excessive radial conduction heat loss. The edge flame oscillation can be characterized well by one curve with Strouhal number and Peclet number.