• Title/Summary/Keyword: Constant Pressure System

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Dual-band Slotted Patch Antenna with Diagonally Offset Deed for GPS and WLAN

  • Lee, Dong-Jun;Shim, Duk-Sun;Kim, Hyung-Kyu;Kim, Hyeong-Seok
    • KIEE International Transactions on Electrophysics and Applications
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    • v.4C no.6
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    • pp.310-313
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    • 2004
  • Spurred by the constant pressure to achieve miniaturization, researchers have designed many different types of compact antennas. One such type is the slotted patch antenna used for dual band operation. In this paper, we propose a novel method of selecting the feeding point of the antenna, which results in superior antenna performance in terms of return loss. Computer simulations verify the validity of the proposed method.

The Reduction of Unburned Hydrocarbons on the Direct-Injection Stratified-Charge Combustion Method by Hydrogen Addition (직접분사 성층연소방식에서 수소 첨가에 의한 미연 탄화수소의 저감)

  • 홍명석;김경석
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.4
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    • pp.46-57
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    • 1996
  • The direct injection stratified charge(DISC) engine enhances the fuel tolerance and the antiknock tendency. This enhanc3d antiknock tendency allows use of a higher compression ratio which results in higher thermal efficiency. But its actual utilization is prevented by high emission combustion time and wall quenching will be the main causes of increasing unburned hydrocarbons in DISC system. In order to solve this problem, small aount of hydrogen was added to the charging air or injected fuel. The effects of hydrogen addition were examined experimentally by radial fuel injection using a pancake-type constant volume bomb. In case of the hydrogen addition to the charge of air, the combustion the amount of hydrogen. In case of the hydrogen addition to the fuel, the combustion pressure was significantly increased.

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Dispersion Characteristics of Sprays under the Condition of Solid Body Rotating Swirl (강체 선회유동 조건에서의 분무 분산 특성에 관한 연구)

  • 이충훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.6
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    • pp.16-23
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    • 2001
  • Spray dispersion in high pressure diesel engines have been simulated experimentally with a special emphasis on the effect of swirl by using a liquid injection technique. A constant volume chamber was designed to be rotatable in order to generate a continuous swirl and to have the flow field closely resembling a solid body rotation. Emulsified fuel was injected into the chamber and the developing process of fuel sprays was visualized. The effect of swirl on the spray dispersion was quantified by calculating non-dimensionalized dispersion area according to the spray tip penetration length. The results show that the effect of swirl on the spray dispersion is different between short and long spray penetrations. For short range of spray tip penetration, the effect of swirl on spray dispersion is quite small. However, as the spray tip is penetrated into longer distance in spray chamber, the effect of swirl on spray dispersion becomes larger. These results can be used as a basic data for designing combustion chamber and injection system of direct injection diesel engine.

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A study on Spray Characteristic of Fuel Injection Nozzle with Geometrical Shape Changes of Needle Valve (연료분사노즐의 니들밸브 형상변화에 따른 분무특성에 관한 연구)

  • 채재우
    • Journal of the korean Society of Automotive Engineers
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    • v.9 no.4
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    • pp.35-40
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    • 1987
  • The experimental study, using constant pressure injection system, is carried out to investigate the effect of the geometrical shape changes of the needle valve of the effective flow area, the spray angle and the Sauter's Mean Diameter according to needle valve lift for a pintle-type injection nozzle. The results are as follows: 1) With the increase of the needle valve lift, the effective flow area is increased, the spray angle is at first increased and later decreased, and the Sauter's Mean Diameter is decreased. 2) It is also shown that the spray angle is maximum at the rapidly increased region of the effective flow area.

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Discharge Characteristics of a KSTAR NBI Ion Source

  • Chang Doo-Hee;Oh Byung-Hoon
    • Nuclear Engineering and Technology
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    • v.35 no.3
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    • pp.226-233
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    • 2003
  • The discharge characteristics of a prototype ion source was investigated, which was developed and upgraded for the NBI (Neutral Beam Injection) heating system of KSTAR (Korea Superconducting Tokamak Advanced Research). The ion source was designed for the arc discharge of magnetic bucket chamber with multi-pole cusp fields. The ion source was discharged by the emission-limited mode with the control of filament heating voltage. The maximum ion density was 4 times larger than the previous discharge controlled by a space-charge-limited mode with fully heated filament. The plasma (ion) density and arc current were proportional to the filament voltage, but the discharge efficiency was inversely proportional to the operating pressure of hydrogen gas. The maximum ion density and arc current were obtained with constant arc voltage ($80{\sim}100V$), as $8{\times}10^{11}cm^{-3}$ and 1200 A, respectively. The estimated maximum beam current was about 35 A, extracted by the accelerating voltage of 80kV.

A Numerical Analysis of Polymer Flow in Thermal Nanoimprint Lithography

  • Kim, Nam-Woong;Kim, Kug-Weon;Lee, Woo-Young
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.3
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    • pp.29-34
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    • 2010
  • Nanoimprint lithography (NIL) is an emerging technology enabling cost effective and high throughput nanofabrication. To successfully imprint a nanometer scale patterns, the understanding of the mechanism in nanoimprint forming is essential. In this paper, a numerical analysis of polymer flow in thermal NIL was performed. First, a finite element model of the periodic mold structure with prescribed boundary conditions was established. Then, the volume of fluid (VOF) and grid deformation method were utilized to calculate the free surfaces of the polymer flow based on an Eulerian grid system. From the simulation, the velocity fields and the imprinting pressure for constant imprinting velocity in thermal NIL were obtained. The velocity field is significant because it can directly describe the mode of the polymer deformation, which is the key role to determine the mechanism of nanoimprint forming. Effects of different mold shapes and various thicknesses of polymer resist were also investigated.

A semi-analytical solution to spherical cavity expansion in unsaturated soils

  • Tang, Jianhua;Wang, Hui;Li, Jingpei
    • Geomechanics and Engineering
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    • v.25 no.4
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    • pp.283-294
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    • 2021
  • This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

Adsorption of Aromatic Compounds on a QCM System Coated with Polymer Films (고분자 필름이 코팅된 QCM 시스템에 의한 방향족 화합물의 흡착)

  • Hwang, Min-Jin;Shim, Wang-Geun;Moon, Hee
    • Korean Chemical Engineering Research
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    • v.51 no.2
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    • pp.233-239
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    • 2013
  • A quartz crystal microbalance (QCM) system coated with poly (isobutylene), polystyrene, and poly (methyl methacrylate) has been prepared to measure the adsorption amounts of benzene, toluene, and p-xylene at very low pressures. The resonant frequency shift of the QCM system is proportional to the increase in pressure in all experiments. The Henry's constants for all adsorbates on the polymer films are obtained from experimental data and compared with the minimum adsorption potential energies between adsorbates and the polymer films. In general, there is an explicit correlation between adsorption amount and the minimum adsorption potential energy.

Parameter Reduction in Digital Adaptive Flight Control System for Spaceplanes

  • Togasaki, Yoshihiro;Shimada, Yuzo;Uchiyama, Kenji
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.995-1000
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    • 2004
  • A digital adaptive flight control system is presented for a Japanese automatic landing flight experiment vehicle (ALFLEX). In previous adaptive control systems based on a linear-parameter-varying (LPV) form, the output behavior was excellent, while the behavior of the adjusted parameters was unsatisfactory. In the present study, to obtain a more appropriate parameter adjustment law, the relationship between the coefficient matrices in a continuous-time state equation and the coefficients of a pulse transfer function in a discrete system for conventional aircraft is investigated. As a result, it is revealed that the coefficients of the numerator can be treated as a linear function of dynamic pressure (linear-parameter-varying: LPV), while the coefficients of the denominator can be treated as constant (linear-time-invariant: LTI). From the above analysis, an improved parameter adjustment law is derived by reducing the number of the adjustment parameters. Simulation results also revealed both good output tracking and good parameter adjustment compared with the previous results.

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Fault Detection and Diagnosis Simulation for CAV AHU System (정풍량 공조시스템의 고장검출 및 진단 시뮬레이션)

  • Han, Dong-Won;Chang, Young-Soo;Kim, Seo-Young;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.10
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    • pp.687-696
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    • 2010
  • In this study, FDD algorithm was developed using the normalized distance method and general pattern classifier method that can be applied to constant air volume air handling unit(CAV AHU) system. The simulation model using TRNSYS and EES was developed in order to obtain characteristic data of CAV AHU system under the normal and the faulty operation. Sensitivity analysis of fault detection was carried out with respect to fault progress. When differential pressure of mixed air filter increased by more than about 105 pascal, FDD algorithm was able to detect the fault. The return air temperature is very important measurement parameter controlling cooling capacity. Therefore, it is important to detect measurement error of the return air temperature. Measurement error of the return air temperature sensor can be detected at below $1.2^{\circ}C$ by FDD algorithm. FDD algorithm developed in this study was found to indicate each failure modes accurately.