• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.188-194
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• 2007

New diesel engines equipped with common-rail injection systems and advanced engine management control allow drastic decreases in the production of particulate matters and nitrogen oxides with a significant advantage in terms of the fuel consumption and $CO_2$ emissions. Nevertheless, the contribution of exhaust gas after treatment in the ultra low emission vehicles conception has become unavoidable today. Recently the passive type DPF(Diesel Particulate Filter Trap) system for diesel passenger vehicle has been manufactured into mass production from a French automotive maker since the year of 2000. This passive DPF system fully relies on the catalytic effects from additives blended into the diesel fuel and additives injected into the DPF system. In this study, the effects of PM regeneration in the commercial diesel passenger vehicle with the passive type DPF system were investigated in chassis dynamometer CVS(constant volume sampler)-75 mode. As shown in this experimental results, the DPF regeneration was observed at temperature as low as $350^{\circ}C$. And the engine-controlled the DPF regeneration founded to be one of the most promising regeneration technologies. Moreover, the durability of this DPF system was evaluated with a season weather in terms of the differential pressure and exhaust gas temperature traces from a road test during the total mileage of 80,000km.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.31-38
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• 2016

Most of propellants that is used widely in the world release toxic gases such as methane gas and carbon dioxide during combustion which are noxious to the environment. This study established a synthetic process of a high nitrogen containing derivative of triazole, 4,5-bis(azidomethyl)-methyl-1,2,3-triazole (DAMTR), which can be applied as energetic plasticizer to environmental concerns. Also, the compound was characterized by NMR, IR spectroscopy, and physical properties such as glass transition temperature, melting point, decomposition temperature, density, impact sensitivity, viscosity and volatility were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAMTR were calculated using Gaussian 09 and EXPLO5 programs.

• Elastomers and Composites
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• v.34 no.1
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• pp.3-10
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• 1999

Kinetics of solution photopolymerization of acrylonitrile(AN) with sensitizer, such as $NaSCN,\;KSCN,\;Ba(SCN)_2,\;NH_4SCN,\;ZnCl_2$ and $Na_2SeO_3$, were studied using UV crosslinker at various monomer concentrations($1.8{\sim}7.58mo1/1$), sensitizer concentrations($10{\sim}60%$), reaction temperature($10{\sim}70^{\circ}C$), energy intensities($1,000{\sim}9,900{\mu}J/cm^2$) at isothermal condition under nitrogen atmosphere. Under the irradiation of high pressure mercury lamp(${\lambda}=365nm$). High conversion and uniform molecular weight were obtained compare to thermal polymerization at reaction temperature of $50^{\circ}C$, reaction time of 3hr and 50% NaSCN without any initiator. Their kinetic model was as follows : $R_p=0.0142[M]^{0.82}[I]^{0.49}[S]^{0.52}$ exp(-1.33/RT).

• Journal of Industrial Technology
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• v.18
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• pp.249-258
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• 1998

In this paper, we investigated the post-combustion removal of nitrogen oxide($NO_x$) and sulfur oxide($SO_x$) which is based on the gas to particle conversion process by the pulsed corona discharge. Under normal pressure, the pulsed corona discharge produces the energetic free electrons which dissociate gas molecules to form the active radicals. These radicals cause the chemical reactions that convert $SO_x$ and $NO_x$ into acid mists and these mists react with $NH_3$ to form solid particles. Those particles can be removed from the gas stream by conventional devices such as electrostatic precipitator or bag filter. The reactor geometry was coaxial with an inner wire discharge electrode and an outer ground electrode wrapped on a glass tube. The simulated flue gas with $SO_x$ and $NO_x$ was used in the experiment. The corona discharge reactor was more efficient in removing $SO_x$ and $NO_x$ by adding $NH_3$ and $H_2O$ in the gas stream. We also measured the removal efficiency of $SO_x$ and $NO_x$ in a cylinder type corona discharge reactor and obtained more than 90 % of removal efficiency in these experimental conditions. The effects of process variables such as the inlet concentrations of $SO_x$, $NH_3$ and $H_2O$, residence time, pulse frequencies and applied voltages were investigated.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.706-714
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• 1995

Silicon oxide thin films were deposited by remote plasma chemical vapor deposition (RPCYD). The effect of the operating variables, such as plasma power, deposition temperature and partial pressure of reactant on the material Properties of the silicon oxide film was investigated. By XPS, it was found out that the film was suboxide (O/Si<2) and small amount of nitrogen due to the plasma excitation was accumulated at the Si/SiO$_2$interface. The amount of dangling bonds at the Si/SiO$_2$interfaces were measured by ESR and the concentration of hydrogen bond was obtained by SIMS and FT-IR. The bond angle distribution(d$\theta$/$\theta$) was shown to be similiar to thermal oxide above 20$0^{\circ}C$ but the etch rate was higher than that of the thermal oxides due to the structural difference and the stress between silicon substrate and silicon oxide film.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.530-537
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• 2012

This work experimentally investigates that Diesel-DME blended fuel influences combustion characteristics and emissions (NOx, CO, HC, smoke) in a single-cylinder DI diesel engine. Diesel is used as a main fuel and DME is blended for the use of its quick evaporating characteristics. Diesel and DME are blended by the method of weight ratio. Weight ratios for Diesel and DME are 95:5 and 90:10 respectively and the both ratios have been used altogether in blended fuel. The experiments are conducted in this study single cylinder engine is equipped with common rail and injection pressure is 700 bar at 1200 rpm. The amount of injected fuels is adjusted to obtain the fixed input calorie value as 972.2 J/cycle in order to compare with the fuel conditions. DME is compressed to 15 bar by using nitrogen gas thus it can be maintained the liquid phase. In this study, different system compared others paper is common rail system, also there is combustion and emission about compared DME and diesel fuel. It is expected to be utilized about blended fuel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7745-7753
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• 2015

Gas springs of the television is to control the piston speed when operating under along stroke(200~300 mm, television elevation)is possible. User by this principle is capable of elevation adjustment. First carried out a flow analysis of the piston. A piston speed adjustment technique for precise pipe type cross-section was examined. The piston structure for flow rate control and elevation action is proposed. This study is the development of a gas spring of more than 50 inch television with a large television stand. Hollow piston rod for optimal control(the outer diameter 19.9 mm, the inner diameter 13.9 mm) was injected into the nitrogen gas(0.3 mm/s) in. As a result, the flow rate the pressure drop of the piston rod as the increase was increased without any change of the external force. As a result, control of the displacement via the gas spring is possible.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.29-30
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• 2001

This paper presents some results of plasma nitriding on hard chromium deposit. The substrates were C45 steel and $30~50{\;}\mu\textrm{m}$ of chromium deposit by electroplating was formed. Plasma nitriding was carried out in a plasma nitriding system with $95NH_3{\;}+{\;}SCH_4$ atmosphere at the pressure about 600 Pa and different temperature from $450^{\circ}C{\;}to{\;}720^{\circ}C$ for various time. Optical microscopy and X-ray diffraction were used to evaluate the characteristics of surface nitride layer formed by nitrogen diffusion from plasma atmosphere inward iCr coating and interface carbide layer formed by carbon diffusion from substrate outward Cr coating. The microhardness was measured using microhareness tester at the load of 100 gf. Corrosion resistance was evaluated using the potentiodynamic measurement in 3.5% NaG solution. A saturated calomel electrode (SiCE) was used as the reference electrode. Fig.1 shows the typical microstructures of top surface and cross-section for nitrided and unnitrided samples. Aaer plasma nitriding a sandwich structure was formed consisting of surface nitride layer, center chromium layer and interface carbide layer. The thickness of nitride and carbide layers was increased with the increase of processing temperature and time. Hardness reached about 1000Hv after nitriding while 900Hv for unnitrided hard chromium deposit. X-ray diffraction indicated that surface nitrided layer was a mixture of $Cr_2N$ and CrN at low temperature and erN at high temperature (Fig.2). Anodic polarization curves showed that plasma nitriding can greatly improve the corrosion resistance of chromium e1ectrodeposit. After plasma nitriding, the corrosion potential moved to noble direction and passive current density was lower by 1 to 4 orders of magnitude compared with chromium deposit(Fig.3).

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.512-521
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• 2017

This paper reports development process of a university-based sounding rocket using simplified hybrid rocket propulsion system for low-altitude flight application. A hybrid propulsion system was tried to be designed with as few components as possible for more economical, simpler and safer propulsion system, which is essential for the small scale sounding rocket operation as a CanSat carrier. Using blow-down feeding system and catalytic ignition as combustion starter, 250 N class hybrid rocket system was composed of three components: a composite tank, valves, and a thruster. With a composite tank filled with both hydrogen peroxide($H_2O_2$) as an oxidizer and nitrogen gas($N_2$) as a pressurant, the feeding pressure was operated in blowdown mode during thruster operation. The $MnO_2/Al_2O_3$ catalyst was fabricated for propellant decomposition, and ground test of propulsion system showed the almost theoretical temperature of decomposed $H_2O_2$ at the catalyst reactor, indicating sufficient catalyst efficiency for propellant decomposition. Auto-ignition of the high density polyethylene(HDPE) fuel grain successfully occurred by the decomposed $H_2O_2$ product without additional installation of any ignition devices. Performance test result was well matched with numerical internal ballistics conducted prior to the experimental propulsion system ground test. A sounding rocket using the developed hybrid rocket was designed, fabricated, flight simulated and launch tested. Six degree-of-freedom trajectory estimation code was developed and the comparison result between expected and experimental trajectory validated the accuracy of the developed trajectory estimation code. The fabricated sounding rocket was successfully launched showing the effectiveness of the simplified hybrid rocket propulsion system.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.2
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• pp.85-94
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• 2006

A splanchic artery occlusion for 90 min followed by reperfusion of the mesenteric circulation resulted in a severe form of circulatory shock, characterized by endothelial dysfunction, severe hypotension, marked intestinal tissue injury, and a high mortality rate. The effect of defibrotide, a complex of single-stranded polydeoxyribonucleotides having antithrombotic effect, was investigated in a model of splanchnic artery occlusion (SAO) shock in urethane anesthetized rats. Occlusion of the superior mesenteric artery for 90 min produced a severe shock state, resulting in a fatal outcome within 120 min of reperfusion in many rats. Defibrotide (10 mg/kg body weight) 10 min prior to reperfusion significantly improved mean arterial blood pressure in comparison to vehicle treated rats (p＜0.05). Defibrotide treatment also significantly attenuated in the increase of plasma amino nitrogen concentration, intestinal myeloperoxidase activity, intestinal lipid peroxidation, infiltration of neutrophils in intestine and thrombin induced adherence of neutrophils to superior mesentric artery segments. Superoxide anion and hydrogen peroxide production in $1{\mu}M$ formylmethionylleucylphenylalanine (fMLP)-activated PMNs was inhibited by defibrotide in a dose-dependent fashion. Defibrotide effectively scavenged hydrogen peroxide, but not hydroxyl radical. Treatment of SAO rats with defibrotide inhibited tumor necrosis factor-${\alpha}$, and interleukin-1${\beta}$ productions in blood in comparison with untreated rats. These results suggest that defibrotide partly provides beneficial effects by preserving endothelial function, attenuating neutrophil accumulation, and antioxidant in the ischemic reperfused splanchnic circulation