• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.4
• /
• pp.305-311
• /
• 2003

DOP aerosol particles with geometric mean diameter of 0.5-3.0 ${\mu}{\textrm}{m}$, geometric standard deviation of 1.1-1.3 and total number concentration of 1,500-8,000 Particles/㎤ were used to determine collection efficiencies of a packed wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. Meanwhile, as for the particle size variation, all of the collection efficiency curves increased rapidly between 0.57-1.41${\mu}{\textrm}{m}$ for the range of water injection rate above 30 L/min. It was also seen that the collection efficiency of a packed wet scrubber is mainly governed by the mechanism of inertial impaction.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.766-769
• /
• 2002

We have seen the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine(CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate)(PEDOT:PSS) in a device structure of ITO/buffer/TPD/$Alq_3$/Al. Polymer PVK and PEDOT:PSS buffer layer was made using spin casting method and the CuPc layer was made using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature with a thickness variation of buffer layer. We have obtained an improvement of the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer are used, respectively. The enhancement of the efficiency is attributed to the improved balance of holes and elelctrons due to the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer functions as a hole-injection supporter and the PVK layer as a hole-blocking one.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.17 no.4
• /
• pp.141-148
• /
• 2009

Afterfogging of the regenerative gas turbine system has an advantage over inlet fogging in that the high outlet temperature of air compressor makes the injection of more water and the recuperation of more exhaust heat possible. This study investigates the effects of turbine inlet temperature (TIT) on the performance of regenerative gas turbine system with afterfogging through a thermodynamic analysis model. For the standard ambient conditions and the water injection ratios up to 5%, the variation of system performance including the thermal efficiency is numerically analyzed with respect to the variations of TIT and pressure ratio. It is also analyzed how the maximum thermal efficiency, net specific work, and pressure ratio itself change with TIT at the peak points of thermal efficiency curve. All of these are found to increase almost linearly with the increases of both TIT and water injection ratio.

• Journal of the Optical Society of Korea
• /
• v.12 no.4
• /
• pp.303-308
• /
• 2008

Directly modulated fiber-optic links generally suffer higher link loss and larger signal distortion than externally modulated links. These result from the electron-photon conversion loss and laser modulation dynamics. As a method to overcome the drawbacks, we have experimentally demonstrated the RF performance of directly modulated, ultra-strong injection-locked gain-lever distributed Bragg reflector (DBR) lasers. The free-running DBR lasers exhibit an improved amplitude modulation efficiency of 12.4 dB under gain-lever modulation at the expense of linearity. By combining gain-lever modulation with ultra-strong optical injection locking, we can gain the benefits of both improved modulation efficiency from the gain-lever effect, plus improved linearity from injection locking. Using an injection ratio of R=11 dB, a 23.4-dB improvement in amplitude response and an 18-dB improvement in spurious-free dynamic range have been achieved.

• Journal of the Korean Society for Environmental Technology
• /
• v.19 no.6
• /
• pp.570-575
• /
• 2018

The various of raw wastewater inflows to the industrial wastewater treatment plants everyday. This makes it difficult to operate the coagulation and flocculation efficiently as a pretreatment process for the industrial wastewater treatment. Additionally, it causes loads on evaporation and membrane facilities which are the posttreatment and alternative processes. For this reason, this study sampled raw wastewater before and after the NaOH injection. An experiment was conducted to compare the coagulation characteristics according to the methods of coagulant injection (single injection, simultaneous injection, consecutive injection, and inverse injection) aiming at efficient treatment of industrial wastewater. The coagulation experiment was conducted using a jar tester. The TDS removal efficiency by the coagulant injection methods increased in the order of consecutive injection (2.8 %) < single injection (3.9 %) < simultaneous injection(8.1 %) < inverse injection(9.6 %); the TOC removal efficiency grew in the order of single injection (84.3 %) < inverse injection (86.2 %) < consecutive injection (88.6 %) < simultaneous injection (89.1 %); the turbidity removal efficiency grew from single injection (99.7 %) < consecutive injection (99.8 %) ${\fallingdotseq}$ inverse injection (99.8 %) < simultaneous injection (99.9 %). These results show that the simultaneous inorganic coagulant-polymer coagulant injection method was more efficient than the consecutive injection method (inorganic coagulant ${\rightarrow}$ polymer coagulant).

• Transactions of the Korean Society of Automotive Engineers
• /
• v.23 no.2
• /
• pp.169-177
• /
• 2015

In this study we investigated the regeneration methods for the lean $NO_x$ trap (LNT) catalyst in a 2.2L direct injection diesel engine. The regeneration methods were 1) in-cylinder post fuel injection and 2) external fuel injection strategy. The in-cylinder post fuel injection method uses in-cylinder injectors with the addition of the post fuel injection to supply enough reductants such as CO, $H_2$, THC. The external fuel injection method was enabled by installing a fuel injector with a wide spray angle before the LNT catalyst. Through the engine experiment, the $NO_x$ conversion efficiency, the amount of reductant exhaust gases, fuel consumption, and temperature behavior in the LNT catalyst were evaluated and compared for the two regeneration methods.

• Journal of ILASS-Korea
• /
• v.26 no.2
• /
• pp.96-103
• /
• 2021

In order to improve the overall efficiency and meet the emission regulations of boiler systems, the heat exchanging methods between inlet air and exhaust gas have been used in boiler systems, named as the waste-heat-recovery condensing boiler. Recently, to further improve the overall efficiency and to reduce the NOx emission simultaneously, the concept of the water injection into the inlet air is introduced. This study suggests the models for the optimized design parameters of water injection for waste-heat-recovery condensing boilers and performs the analysis regarding the water injection amount and droplet sizes for the optimized water injection. At first, the required amount of the water injection was estimated based on the 1^st law of thermodynamics under the assumption of complete evaporation of the injected water. The result showed that the higher the inlet air and exhaust gas temperature into the heat exchanger, the larger the amount of injected water is needed. Then two droplet evaporation models were proposed to analyze the required droplet size of water injection for full evaporation of injected water: one is the evaporation model of droplet in the inlet air and the other is that on the wall of heat exchanger. Based on the results of two models, the maximum allowable droplet sizes of water injection were estimated in various boiler operating conditions with respect to the residence time of the inlet air in the heat exchanger.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.193-200
• /
• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.380-380
• /
• 2010

Currently, organic light-emitting diodes (OLEDs) have been proven of their readiness for commercialization in terms of lifetime and efficiency. In accordance with emerging new technologies, enhancement of light efficiency and extension of application fields are required. Particularly inverted structures, in which electron injection occurs at bottom and hole injection on top, show crucial advantages due to their easy integration with Si-based driving circuits for active matrix OLED as well as large open area for brighter illumination. In order to get better performance and process reliability, usually a proper buffer layer for carrier injection is needed. In inverted top emission OLED, the buffer layer should protect underlying organic materials against destructive particles during the electrode deposition, in addition to increasing their efficiency by reducing carrier injection barrier. For hole injection layers, there are several requirements for the buffer layer, such as high transparency, high work function, and reasonable electrical conductivity. As a buffer material, a few kinds of transition metal oxides for inverted OLED applications have been successfully utilized aiming at efficient hole injection properties. Among them, we chose 2 nm of $WO_3$ between NPB [N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] and Au (or Al) films. The interfacial energy-level alignment and chemical reaction as a function of film coverage have been measured by using in-situ ultraviolet and X-ray photoelectron spectroscopy. It turned out that the $WO_3$ interlayer substantially reduces the hole injection barrier irrespective of the kind of electrode metals. It also avoids direct chemical interaction between NPB and metal atoms. This observation clearly validates the use of $WO_3$ interlayer as hole injection for inverted OLED applications.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.3
• /
• pp.45-51
• /
• 2012

This work was investigated 2-stage injection strategy on combustion and emissions in a direct injection compression-ignition engine fueled with DME. Single cylinder engine was equipped with common rail. Injection pressure was 700bar, dSOI between the main injection and the pilot injection was varied. Diesel was used as compared fuel of DME in all cases. The results was shown that maximum pressure was higher than all cases and its amount of DME and diesel was similar. Regardless the pilot injection, the main fuel injection timing was same. The heat release rate of the main injection for diesel was high while that of pilot injection for DME was high. The THC was very low regardless of the fuel type and injection strategy. In the single injection, NOx was increased to retard of main injection timing regardless of the fuel type. NOx emissions was decreased with the retardation of the main injection timing regardless of the fuel type in the case of 2-stage injection strategy.